Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

You’ve supercharged your research process with ACS and Mendeley!

STEP 1:
Click to create an ACS ID

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

MENDELEY PAIRING EXPIRED
Your Mendeley pairing has expired. Please reconnect
ACS Publications. Most Trusted. Most Cited. Most Read
Double Doping of a Low-Ionization-Energy Polythiophene with a Molybdenum Dithiolene Complex
More

OR SEARCH CITATIONS

My Activity
Publications
CONTENT TYPES

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:Chem. Mater. 2022, 34, 12, 5673-5679
  • Open Access
Article

Double Doping of a Low-Ionization-Energy Polythiophene with a Molybdenum Dithiolene Complex
Click to copy article linkArticle link copied!

  • Emmy Järsvall
    Emmy Järsvall
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
    More by Emmy Järsvall
  • Till Biskup
    Till Biskup
    Physical Chemistry, University of Saarland, Saarbrücken 66123, Germany
    More by Till Biskup
    Orcidhttps://orcid.org/0000-0003-2913-0004
  • Yadong Zhang
    Yadong Zhang
    Georgia Institute of Technology, School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332-0400, United States
    Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
    More by Yadong Zhang
  • Renee Kroon
    Renee Kroon
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
    Laboratory of Organic Electronics, Linköping University, 60174 Norrköping, Sweden
    More by Renee Kroon
    Orcidhttps://orcid.org/0000-0001-8053-4288
  • Stephen Barlow
    Stephen Barlow
    Georgia Institute of Technology, School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332-0400, United States
    Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
    More by Stephen Barlow
    Orcidhttps://orcid.org/0000-0001-9059-9974
  • Seth R. Marder
    Seth R. Marder
    Georgia Institute of Technology, School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332-0400, United States
    Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
    Departments of Chemical and Biological Engineering and of Chemistry, University of Colorado Boulder, Boulder, Colorado 80303, United States
    More by Seth R. Marder
  • Christian Müller*
    Christian Müller
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
    *Email: [email protected]
    More by Christian Müller
    Orcidhttps://orcid.org/0000-0001-7859-7909
Open PDFSupporting Information (1)

Chemistry of Materials

Cite this: Chem. Mater. 2022, 34, 12, 5673–5679
Click to copy citationCitation copied!
https://doi.org/10.1021/acs.chemmater.2c01040
Published June 13, 2022

Copyright © 2022 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Abstract

Click to copy section linkSection link copied!
High Resolution Image
Download MS PowerPoint Slide

Doping of organic semiconductors is crucial for tuning the charge-carrier density of conjugated polymers. The exchange of more than one electron between a monomeric dopant and an organic semiconductor allows the polaron density to be increased relative to the number of counterions that are introduced into the host matrix. Here, a molybdenum dithiolene complex with a high electron affinity of 5.5 eV is shown to accept two electrons from a polythiophene that has a low ionization energy of 4.7 eV. Double p-doping is consistent with the ability of the monoanion salt of the molybdenum dithiolene complex to dope the polymer. The transfer of two electrons to the neutral dopant was also confirmed by electron paramagnetic resonance spectroscopy since the monoanion, but not the dianion, of the molybdenum dithiolene complex features an unpaired electron. Double doping allowed an ionization efficiency of 200% to be reached, which facilitates the design of strongly doped semiconductors while lessening any counterion-induced disruption of the nanostructure.

This publication is licensed under

CC-BY 4.0 .
  • cc licence
  • by licence
Copyright © 2022 The Authors. Published by American Chemical Society

Subjects

what are subjects

Introduction

Click to copy section linkSection link copied!
Organic semiconductors attract a great deal of attention since they enable the development of lightweight, flexible, and biocompatible electronic devices for applications from energy harvesting and storage to bioelectronics, which cannot be achieved with inorganic semiconductors alone. (1,2) Doping is a widely used tool to tune the charge-carrier density, which allows the electrical properties of organic semiconductors to be optimized. (3−5) The process typically involves the addition of a dopant, such as an organic molecule, a metal–organic complex, or a metallic salt, that undergoes an electron transfer with the organic semiconductor. (5) Electron transfer readily occurs in the case of a favorable energetic offset between the two materials. In the case of p-doping, for example, it is beneficial if the dopant has an electron affinity (EA) that is larger than the ionization energy (IE) of the semiconductor, i.e., EAdopant ≥ IEsemiconductor. Here, it is important to note that the EA and IE, which are often estimated from electrochemical methods, can take on very different values once the dopant and semiconductor are mixed. (6) Furthermore, the structural and energetic disorder inherent to many organic semiconductors leads to a broad density of states, which may facilitate some degree of electron transfer despite an unfavorable energy offset. (7,8) Provided that each p-dopant accepts one electron from the semiconductor, i.e., the pair undergoes integer charge transfer, one polaron is created per dopant molecule, resulting in an ionization efficiency of 100%. The ionization efficiency is reduced to less than 100% in the case that only partial charge transfer occurs, if there is an unfavorable energetic offset between EAdopant and IEsemiconductor or if the dopant molecules aggregate. The presence of excess dopants and dopant aggregates unduly disrupts the nanostructure of the semiconductor, which tends to negatively affect the electrical properties. (9−11)
We have recently reported that quinodimethane-type dopants with a sufficiently high EAdopant can accept two electrons from a low-IE conjugated polymer, resulting in an ionization efficiency of 200%. (12) This type of double doping was observed for a thienothiophene-based copolymer with tetraethylene glycol side chains, for which IEpolymer = 4.5 eV, doped with either 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), for which EAF4TCNQ = 5.2 eV, or 1,3,4,5,7,8-hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ), for which EAF6TCNNQ = 5.3 eV (electron affinity estimated from half-wave potential E1/2 vs ferrocene/ferrocenium, Fc/Fc+; EAdopant = 5.1 eV + E1/2). (12) The electron affinities of the anions of these two quinodimethane-type dopants, EAdopant–, are estimated to remain sufficiently low that EAdopant– > IEpolymer, allowing each dopant to accept a second electron from the polymer. Other dopants that can give rise to more than one polaron include the dimers formed by certain 19-electron organometallic sandwich compounds or by benzoimidazoline radicals, the overall reaction of which with a host results in the formation of two monomeric dopants and the release of two electrons. (7) These dopant dimers, however, have approximately twice the molecular volume of related monomeric dopants, which reduces the benefit of double doping because it doubles the overall volume that is occupied by counterions. Likewise, multivalent radical cation salts that comprise two or four triphenylamine units can accept two or even four electrons from a conjugated polymer (13,14) but have a close to 2–4 times larger volume compared to the corresponding monovalent radical anion salt tris(4-bromophenyl)ammoniumyl hexachloroantimonate ([TPA–Br3]+[SbCl6]−; Magic Blue). We argue that double doping is preferably achieved without increasing the size of the dopant so that fewer dopant molecules must be added to obtain a certain polaron density, which reduces the risk of dopant aggregation and lessens the impact of doping on the nanostructure of the polymer.
Here we ask whether double doping is unique to quinodimethane-type monomeric dopants or whether it is a generic concept that can also be observed for other species. In particular, we investigate doping using the dithiolene complex Mo(tfd-COCF3)3, (15) for which EAMo(tfd-COCF3)3 can be estimated as ca. 5.5 eV (reduction potential Ered ≈ +0.39 V vs decamethylferrocene/decamethylferrocenium, DmFc/DmFc+; EAMo(tfd-COCF3)3 = 5.1 eV + Ered). (16) We note that electrochemically based estimates of the electron affinity are approximate because solvation effects and solid-state polarization effects likely vary between molecules of different sizes and shapes. However, the value of EAMo(tfd-COCF3)3 = 5.5 eV is in reasonable agreement with a value of 5.6 eV measured in the solid state by inverse photoelectron spectroscopy for a related molecule, Mo(tfd)3, for which Ered ≈ +0.28 V vs DmFc/DmFc+. (17) Mo(tfd-COCF3)3 has been used to dope a wide range of conjugated polymers including poly(3-hexylthiophene) (P3HT), (18,19) poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT), (20,21) and a benzodithiophene-based copolymer. (9,22,23) We chose Mo(tfd-COCF3)3 because it can exist both as an anion and dianion, meaning that it can sustain two electron transfer events, and both of these species are known to have reasonable chemical stability (indeed, the neutral dopant is obtained by chemical oxidation of the dianion). (16) The Mo(tfd-COCF3)3 anion electron affinity, EAMo(tfd–COCF3)3–, can be estimated as ca. 4.9 eV (Ered ≈ −0.16 V vs Fc/Fc+), (16) although the potential separation between subsequent redox processes in electrochemical experiments can be highly medium-dependent, (24) meaning there will be a larger uncertainty in this estimate than in those of the electron affinity of neutral molecules. Nevertheless, if EAMo(tfd–COCF3)3– is indeed ca. 4.9 eV, then polymers with an IEpolymer < 4.9 eV should be able to experience double doping when brought in contact with Mo(tfd-COCF3)3. Doping of two polymers was investigated, the polythiophene p(g42T-T) with tetraethylene glycol side chains and a low IEp(g42T–T) = 4.7 eV (oxidation potential Eox ≈ −0.44 V vs Fc/Fc+; IEp(g42T–T) = 5.1 eV + Eox) (25) and the thiophene-quinoxaline copolymer TQ1, (26,27) which features a large IETQ1 = 5.5 eV (Eox ≈ 0.37 V vs Fc/Fc+; (27) see Figure 1 for chemical structures and energy levels). We here show that p(g42T-T) readily undergoes double doping by Mo(tfd-COCF3)3.

Figure 1

Figure 1. Energy diagram showing the energy levels that are relevant for charge transfer from polymers p(g42T-T) and TQ1 to the p-type dopant Mo(tfd-COCF3)3.

High Resolution Image
Download MS PowerPoint Slide

Results and Discussion

Click to copy section linkSection link copied!
The dopant investigated here can exist as a neutral complex, Mo(tfd-COCF3)3, as well as a salt comprising either its anion or dianion. The dianion salt Mo(tfd-COCF3)3(Et4N)2 is a precursor for the synthesis of Mo(tfd-COCF3)3, as reported previously. (15,16) Neutral Mo(tfd-COCF3)3 was prepared by oxidizing the dianion salt using NOPF6. The anion salt, instead, was prepared by the comproportionation of equimolar amounts of Mo(tfd-COCF3)3 and the dianion salt Mo(tfd-COCF3)3 (Et4N)2. All three species give rise to distinct ultraviolet–visible–near-infrared (UV–vis–NIR) absorbance spectra (Figure 2a). These absorptions, however, occur at wavelengths where either neat p(g42T-T) and TQ1 absorb or where polaronic absorbance peaks tend to arise upon doping. Hence, it is challenging to extract information about the presence of different species from optical spectroscopy. Instead, we chose to use electron paramagnetic resonance (EPR) spectroscopy to detect the presence of different species.

Figure 2

Figure 2. (a) UV–vis spectra of Mo(tfd-COCF3)3, [Mo(tfd-COCF3)3]−Et4N+, and [Mo(tfd-COCF3)3]2–(Et4N+)2 dissolved in dichloromethane (DCM). (b) EPR spectra of [Mo(tfd-COCF3)3]−Et4N+ and [Mo(tfd-COCF3)3]2–(Et4N+)2 dispersed in a matrix of poly(ethylene oxide) (PEO; see Figure S4 for nonsmoothed EPR spectra).

High Resolution Image
Download MS PowerPoint Slide
In a first set of experiments, we recorded EPR spectra of the monoanion salt and the dianion salt dispersed in poly(ethylene oxide) (PEO) to mimic the solid-state environment that the two species will experience when dispersed in a p(g42T-T) matrix. The UV–vis–NIR spectra of the monoanion and dianion salt dissolved in dichloromethane (DCM) or in PEO are comparable (Figure S1), which suggests that the PEO matrix does not strongly alter the electronic state of the two species. The monoanion salt gives rise to a distinct EPR signal centered at B0 = 341.4 mT, in agreement with reports for other monoanionic molybdenum tris(dithiolene) complexes, (28−30) while the dianion salt appears spin-silent (Figures 2b and S2–S4), consistent with the sharp NMR spectra reported for [Mo(tfd-COCF3)3]2–, (15) as well as with magnetic susceptibility (30) and computational studies (31) of other molybdenum tris(dithiolene) dianions.
We next studied doped TQ1, which has a high IETQ1 = 5.5 eV that is comparable to EAMo(tfd-COCF3)3. Judging by the ionization energy of TQ1, the polymer can be expected to undergo some electron transfer with neutral Mo(tfd-COCF3)3, but the energy levels of TQ1 and [Mo(tfd-COCF3)3]− should not allow for a second charge transfer event since IETQ1 ≫ EAMo(tfd–COCF3)3–. UV–vis–NIR spectra of TQ1 sequentially doped with Mo(tfd-COCF3)3 reveal clear polaronic absorption bands confirming that electron transfer has indeed occurred (Figure 3a). The EPR spectra for TQ1 doped with Mo(tfd-COCF3)3 consist of two overlapping signals, one at a magnetic field of 342.2 mT and one at a lower magnetic field. We assign the signal at a lower magnetic field to the monoanion of Mo(tfd-COCF3)3 since it appears at the same position as the EPR signal observed for [Mo(tfd-COCF3)3]−Et4N+ (Figures 3b, S5, and S6). This observation suggests that doping of TQ1 with Mo(tfd-COCF3)3 primarily occurs through a single electron transfer event per dopant, resulting in Mo(tfd-COCF3)3 anions that can be detected with EPR spectroscopy.

Figure 3

Figure 3. (a) UV–vis–NIR absorbance spectra displaying the difference in thickness-normalized absorbance Δ(A/d) between the spectra of neat TQ1 and TQ1 doped with Magic Blue or Mo(tfd-COCF3)3. (b) EPR spectra of [Mo(tfd-COCF3)3]−Et4N+ dispersed in a PEO matrix and TQ1 doped with Mo(tfd-COCF3)3. The spectra have been normalized to the maximum in the field range 338–341.5 mT. (c) EPR spectra of TQ1 doped with Magic Blue or Mo(tfd-COCF3)3. The spectra have been normalized to the same amplitude.

High Resolution Image
Download MS PowerPoint Slide
To confirm the plausibility of assigning the EPR signal at 342.2 mT to the polymer polaron, we also recorded EPR spectra of TQ1 doped with Magic Blue, which is a stronger oxidant than Mo(tfd-COCF3)3 and in which the radical cation portion can accept an electron from TQ1 because neutral tris(4-bromophenyl)amine (TPA–Br3) has a very high IETPA–Br3 ≈ 5.7 eV (E1/2 = +0.7 V vs DmFc/DmFc+), (32) i.e., its radical cation [TPA–Br3]+ can be reduced by TQ1 since 5.7 eV > IETQ1. Doping of TQ1 with Magic Blue is confirmed by the appearance of a strong polaron absorption band at 900 nm in recorded UV–vis spectra (Figure 3a). (33) The tris(4-bromophenyl)ammoniumyl cation [TPA–Br3]+ becomes neutral as it receives an electron from the polymer during the doping process, and hence ends up spin-silent. Consequently, the EPR spectrum of doped TQ1 exclusively features a polaron signal. The similarity of the signal at ca. 342.2 mT seen for Mo(tfd-COCF3)3-doped TQ1 to the EPR spectrum of TQ1 doped with Magic Blue confirms that this signal arises from polarons on TQ1 (Figures 3c, S7, and S8).
In a further set of experiments, we studied sequential doping of p(g42T-T) with neutral Mo(tfd-COCF3)3 as well as its anion salt, i.e., the two species were allowed to ingress from a dopant solution into a solid film of the polymer (see the Experimental Section for details). UV–vis–NIR spectroscopy reveals stronger polaron absorption bands at 900 nm and in the near-infrared region for p(g42T-T) doped with the neutral complex, which indicates a higher degree of doping with Mo(tfd-COCF3)3 compared to doping with the monoanion salt (Figure 4a). Moreover, the fact that we can dope p(g42T-T) with the monoanion suggests that double doping is possible for this system. Doping of p(g42T-T) with Mo(tfd-COCF3)3 gives rise to an electrical conductivity of σ = (19.6 ± 0.6) S cm–1, whereas doping with the monoanion salt gives a value of σ = (11.9 ± 0.3) S cm–1. The higher electrical conductivity for p(g42T-T) doped with the neutral complex is also an indication that we have a higher degree of doping, i.e., a larger number of charge carriers in this sample compared to p(g42T-T) doped with the monoanion salt. EPR spectra of neat p(g42T-T) as well as the polymer doped with either neutral Mo(tfd-COCF3)3 or the anion salt all reveal a polaron signal at g = 342.2 mT (Figures 4b and S9). The signal in the case of the neat p(g42T-T) sample likely arises from adventitious oxygen doping of the polymer. In the case of doping with the neutral complex, the recorded EPR spectrum features a broad shoulder at a lower magnetic field around 341 mT, which we explain with the presence of monoanions, i.e., the EPR spectrum is a superposition of the EPR signal of the polaron on the polymer and the EPR signal of the monoanion. The EPR spectrum of p(g42T-T) sequentially doped with the monoanion features a signal at a similar field as the neat, oxygen-doped polymer, and the absence of a broad shoulder around 341 mT suggests that no major fraction of monoanions is present. Since UV–vis–NIR spectroscopy indicates that the polymer was doped, i.e., polarons were generated (see Figure 4a), the majority of monoanions that have entered the polymer film must have accepted an electron from p(g42T-T) and thus became spin-silent dianions.

Figure 4

Figure 4. (a) UV–vis–NIR absorbance spectra displaying the difference in thickness-normalized absorbance Δ(A/d) between the spectra of neat p(g42T-T) and p(g42T-T) sequentially doped with Mo(tfd-COCF3)3 or [Mo(tfd-COCF3)3]−Et4N+. (b) EPR spectra of neat p(g42T-T) and p(g42T-T) sequentially doped with Mo(tfd-COCF3)3 or [Mo(tfd-COCF3)3]−Et4N+. (c) EPR spectra of co-processed p(g42T-T):Mo(tfd-COCF3)3 films (see Figures S9 and S11 for nonsmoothed EPR spectra).

High Resolution Image
Download MS PowerPoint Slide
Finally, we studied a series of p(g42T-T) thin films that were prepared by co-processing the polymer with different amounts of the neutral Mo-complex. The conductivity increases with the amount of dopant (Table 1) and the polaron absorbance increases (see UV–vis–NIR spectra in Figure S10), which is consistent with an increasing polaron concentration. For all co-processed samples, the EPR signal is centered at 342.2 mT, i.e., the position assigned to polarons, and we do not observe any broad shoulder at lower magnetic fields (Figures 4c and S11). However, we instead observe a symmetrical broadening with increasing dopant concentration. We interpret the lack of the low-field shoulder as an indication that no significant amount of monoanions is present and hence the EPR signal solely originates from the polarons. The observed symmetrical broadening of the EPR signal with increasing dopant concentration could be attributed to a spin–spin interaction between nearby polarons. (34) Another explanation for the observed symmetrical broadening could be a lower degree of interchain charge hopping with increasing dopant concentrations resulting in the transition from Lorentzian to Gaussian absorption features. (35)
Table 1. Parameters Quantifying the Extent of Doping and the Resulting Conductivity and Mobility for p(g42T-T) Co-Processed with Different Amounts of Mo(tfd-COCF3)3; Amount of Dopant in mol %, Calculated Relative to the Molar Mass of the Repeat Unit of p(g42T-T), Oxidation Level Oox, i.e., Number of Polarons Per Polymer Thiophene Ring in Percent, Ionization Efficiency ηion, i.e., Number of Polarons Per Added Dopant Molecules in Percent, Number of Polarons Np, Conductivity σ and Mobility μ = σeNp, where e is the Elementary Charge
mol % dopantOox (%)ηion (%)Np (1026 m–3)σ (S cm–1)μ (cm2 V–1 s–1)
53.4 ± 0.2195 ± 30.94 ± 0.020.05 ± 0.010.003 ± 0.001
107.4200a2.01.1 ± 0.10.03 ± 0.01
2013.1 ± 0.2158 ± 2.33.6 ± 0.115 ± 10.26 ± 0.04
a

For 10 mol % dopant, the calculated value of ηion was larger than physically possible and therefore was set to 200%.

We used the UV–vis–NIR spectra of the co-processed samples to estimate the number of polarons Np (Table 1). To estimate Np we compared the thickness-normalized difference in absorbance Δ(A800/d) between doped samples and the neat polymer at 800 nm, where a pronounced sub-bandgap polaronic absorption peak is situated, with the molar attenuation coefficient of the polaronic absorption obtained from electrochemically doped P3HT at 800 nm, ε800 = (4.1 ± 0.2) × 103 m2 mol–1. (19) The Beer–Lambert law Δ(A800/d) = ε800 × Np, where d is the film thickness, was used to estimate Np. We then calculated the oxidation level according to Oox = Np/Nthiophene and ionization efficiency according to ηion = Np/NMo(tfd–COCF3)3, where NMo(tfd–COCF3)3 is the number of molybdenum dithiolene complexes (Table 1). We obtain an ionization efficiency of more than 100% for all studied samples, indicating that double doping occurs even for the samples with a higher doping concentration. For 5 and 10 mol % dopants, we estimate that the ionization efficiency is close to 200%, meaning that each Mo(tfd-COCF3)3 complex accepts two electrons from p(g42T-T). A high degree of double doping explains why we do not observe any clear feature of the monoanion in the EPR spectra of p(g42T-T) co-processed with Mo(tfd-COCF3)3 (Figure 4c). Most of the monoanions that form undergo a second electron transfer event and thus become dianions, which are spin-silent.

Conclusions

Click to copy section linkSection link copied!
We conclude that the molybdenum dithiolene complex Mo(tfd-COCF3)3 can accept two electrons from the conjugated polymer p(g42T-T). The dopant monoanions could be detected with EPR spectroscopy because their signal appears at a lower magnetic field than the signal from the polymer polaron. The absence of a clear monoanion signal in EPR spectra of the polymer co-processed with Mo(tfd-COCF3)3 suggests that only dianions are present, i.e., the dopant underwent two electron transfer events with the polymer. The viability of double doping was confirmed by sequential doping of polymer films with the monoanion salt [Mo(tfd-COCF3)3]−Et4N+, which gave rise to a conductivity of σ = (11.9 ± 0.3) S cm–1 and EPR spectra that did not feature any signal from anions, indicating that each anion had been converted into a spin-silent dianion by accepting one electron from the polymer. Analysis of the UV–vis–NIR spectra of co-processed samples indicated an ionization efficiency of 200% for use of up to 10 mol % Mo(tfd-COCF3)3. It can be anticipated that double doping of polymers with suitable monomeric dopants may allow us to achieve high charge-carrier densities while reducing the number of counterions and hence their collective impact on the nanostructure of semiconductor films.

Experimental Section

Click to copy section linkSection link copied!

Materials

TQ1 (weight- and number-average molecular weights, Mn = 76 kg mol–1 and PDI = 2.6), p(g42T-T) (Mn = 24 kg mol–1, PDI = 3.3), Mo(tfd-COCF3)3, and [Mo(tfd-COCF3)3]−Et4N+ and [Mo(tfd-COCF3)3]2–(Et4N+)2 were prepared according to previously reported procedures. (15,27,36) Poly(ethylene oxide) (PEO, Mw = 200 kg mol–1), [TPA–Br3]+[SbCl6]− (Magic Blue), dichloromethane (DCM, purity > 99.9%), and anhydrous acetonitrile (AcN, purity > 99.8%) were purchased from Sigma-Aldrich. Chlorobenzene (CB, purity > 99%) and chloroform (CHCl3, purity > 99.8%) were obtained from Fisher Scientific. All commercial solvents and the Magic Blue dopant were used as received and without further purification.

Sample Preparation

Polymers were dissolved with a concentration of 10 g L–1 (TQ1 in CB and p(g42T-T) in CHCl3) and spin-cast onto poly(ethylene terephthalate) (PET) films, yielding a film thickness of 50–100 nm. The polymer films were sequentially doped with Magic Blue dissolved in AcN/CHCl3 (3:1, v/v; 0.45 g L–1), Mo(tfd-COCF3)3 in AcN/CHCl3 (3:1, v/v; 2.5 g L–1), and [Mo(tfd-COCF3)3]−Et4N+ in AcN/DCM (3:2, v/v; 2.5 g L–1). The dopant solutions were added on top of the films for 30 s, spun off, and finally the films were rinsed with anhydrous AcN to remove any excess dopant on top of the film. To prepare co-processed p(g42T-T)/Mo(tfd-COCF3)3 samples, p(g42T-T) and Mo(tfd-COCF3)3 were dissolved in AcN/CHCl3 (1:1, v/v; 15 and 5 g L–1). Appropriate volumes of AcN/CHCl3 (1:1, v/v) were then added to the p(g42T-T) solutions before the addition of the Mo(tfd-COCF3)3 solution to maintain a polymer concentration of 5–7.5 g L–1 in each polymer/dopant solution while varying the concentration of Mo(tfd-COCF3)3. The co-processed polymer/dopant solutions were spin-cast onto PET films, yielding a film thickness of 80–200 nm. The calculations of molar percentage were based on the molar mass of the polymer repeat unit and the molar mass of the dopant. Mo(tfd-COCF3)3, [Mo(tfd-COCF3)3]−Et4N+, and [Mo(tfd-COCF3)3]2–(Et4N+)2 were dissolved together with PEO in DCM (4 and 16 g L–1), and the solutions were then spin-cast onto PET films.

UV–vis–NIR Absorption Spectroscopy

Measurements of liquid and solid samples were performed with a PerkinElmer Lambda 1050 spectrometer. Mo(tfd-COCF3)3, [Mo(tfd-COCF3)3]−Et4N+, and [Mo(tfd-COCF3)3]2–(Et4N+)2 solutions for UV–vis–NIR absorption measurements were prepared at a concentration of 1 g L–1 in DCM.

Electron Paramagnetic Resonance

The polymer films coated on PET films were cut to a size of 25 mm × 3 mm and then sealed under nitrogen in a quartz EPR tube. EPR spectra were recorded at room temperature using a Magnettech MS5000 spectrometer (Freiberg Instruments, now Bruker Biospin). All spectra were corrected for the same microwave frequency (9.6 GHz). Data processing and analysis have been performed using the cwepr Python package. (37,38)

Electrical Characterization

The electrical resistivity was measured with a four-point probe setup from Jandel Engineering (cylindrical probe head, RM3000) using collinear tungsten carbide electrodes with an equidistant spacing of 1 mm that were held down with a constant weight of 60 g. The electrical conductivity σ was then calculated according to σ = ((V/I)kt)−1, where V is the voltage, I is the current, k = 4.53 is a geometrical correction factor, and t is the thickness.

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.chemmater.2c01040.

  • UV–vis–NIR spectra as well as angular-dependent and nonsmoothed EPR spectra (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

Click to copy section linkSection link copied!
  • Corresponding Author
  • Authors
    • Emmy Järsvall - Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
    • Till Biskup - Physical Chemistry, University of Saarland, Saarbrücken 66123, Germany;  Orcidhttps://orcid.org/0000-0003-2913-0004
    • Yadong Zhang - Georgia Institute of Technology, School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332-0400, United States;  Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States
    • Renee Kroon - Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden;  Laboratory of Organic Electronics, Linköping University, 60174 Norrköping, Sweden;  Orcidhttps://orcid.org/0000-0001-8053-4288
    • Stephen Barlow - Georgia Institute of Technology, School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332-0400, United States;  Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States;  Orcidhttps://orcid.org/0000-0001-9059-9974
    • Seth R. Marder - Georgia Institute of Technology, School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Atlanta, Georgia 30332-0400, United States;  Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, Colorado 80303, United States;  Departments of Chemical and Biological Engineering and of Chemistry, University of Colorado Boulder, Boulder, Colorado 80303, United States
  • Notes
    The authors declare no competing financial interest.

    EPR raw data and analysis “recipes” used to analyze the EPR data are available online via Zenodo (DOI: 10.5281/zenodo.6592331).

Acknowledgments

Click to copy section linkSection link copied!

The authors acknowledge funding from the Swedish Research Council through grant agreement no. 2018-03824 and the National Science Foundation through a DMREF award, DMR-1729737.

References

Click to copy section linkSection link copied!

This article references 38 other publications.

  1. 1
    Organic Flexible Electronics: Fundamentals, Devices, and Applications, 1st ed.; Cosseddu, P.; Caironi, M., Eds.; Woodhead Publishing: Duxford, UK, 2021.
    Google Scholar
    There is no corresponding record for this reference.
  2. 2
    Simon, D. T.; Gabrielsson, E. O.; Tybrandt, K.; Berggren, M. Organic Bioelectronics: Bridging the Signaling Gap between Biology and Technology. Chem. Rev. 2016, 116, 13009– 13041,  DOI: 10.1021/acs.chemrev.6b00146
    Google Scholar
    2
    Organic Bioelectronics: Bridging the Signaling Gap between Biology and Technology
    Simon, Daniel T.; Gabrielsson, Erik O.; Tybrandt, Klas; Berggren, Magnus
    Chemical Reviews (Washington, DC, United States) (2016), 116 (21), 13009-13041CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. The electronics in people's daily lives rely almost exclusively on electrons as the dominant charge carrier. In stark contrast, biol. systems rarely use electrons but rather use ions and mols. of varying size. Due to the unique combination of both electronic and ionic/mol. cond. in conducting and semiconducting org. polymers and small mols., these materials have emerged in recent decades as excellent tools for translating signals between these two realms and, therefore, providing a means to effectively interface biol. with conventional electronics, thus, the field of org. bioelectronics. Today, org. bioelectronics defines a generic platform with unprecedented biol. recording and regulation tools and is maturing toward applications ranging from life sciences to the clinic. In this Review, the authors introduce the field, from its early breakthroughs to its current results and future challenges.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtVyrur7I&md5=57086c8309a7d360d24fb813f44cb03f
  3. 3
    Lüssem, B.; Riede, M.; Leo, K. Doping of organic semiconductors. Phys. Status Solidi A 2013, 210, 9– 43,  DOI: 10.1002/pssa.201228310
    Google Scholar
    3
    Doping of organic semiconductors
    Luessem, B.; Riede, M.; Leo, K.
    Physica Status Solidi A: Applications and Materials Science (2013), 210 (1), 9-43CODEN: PSSABA; ISSN:1862-6300. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. The understanding and applications of org. semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small org. LED (OLED) displays; other areas of application such as OLED lighting and org. photovoltaics are on the verge of broad commercialization. Org. semiconductors are superior to inorg. ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, elec. doping of org. semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorg. semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evapd. org. layers with mol. dopants. Recently, both p- and n-type mol. dopants have been developed that lead to efficient and stable doping of org. thin films. Due to doping, the cond. of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between org. layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and org. solar cells is highlighted in this review. Overall, controlled mol. doping can be considered as key enabling technol. for many different org. device types that can lead to significant improvements in efficiencies and lifetimes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhvVyrtLbN&md5=3028d24bf630eae80c6ca787ab64e41b
  4. 4
    Jacobs, I. E.; Moulé, A. J. Controlling molecular doping in organic semiconductors. Adv. Mater. 2017, 29, 1703063  DOI: 10.1002/adma.201703063
    Google Scholar
    There is no corresponding record for this reference.
  5. 5
    Scaccabarozzi, A. D.; Basu, A.; Aniés, F.; Liu, J.; Zapata-Arteaga, O.; Warren, R.; Firdaus, Y.; Nugraha, M. I.; Lin, Y.; Campoy-Quiles, M.; Koch, N.; Müller, C.; Tsetseris, L.; Heeney, M.; Anthopoulos, T. D. Doping Approaches for Organic Semiconductors. Chem. Rev. 2022, 122, 4420– 4492,  DOI: 10.1021/acs.chemrev.1c00581
    Google Scholar
    5
    Doping Approaches for Organic Semiconductors
    Scaccabarozzi, Alberto D.; Basu, Aniruddha; Anies, Filip; Liu, Jian; Zapata-Arteaga, Osnat; Warren, Ross; Firdaus, Yuliar; Nugraha, Mohamad Insan; Lin, Yuanbao; Campoy-Quiles, Mariano; Koch, Norbert; Muller, Christian; Tsetseris, Leonidas; Heeney, Martin; Anthopoulos, Thomas D.
    Chemical Reviews (Washington, DC, United States) (2022), 122 (4), 4420-4492CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. Electronic doping in org. materials has remained an elusive concept for several decades. It drew considerable attention in the early days in the quest for org. materials with high elec. cond., paving the way for the pioneering work on pristine org. semiconductors (OSCs) and their eventual use in a plethora of applications. Despite this early trend, however, recent strides in the field of org. electronics have been made hand in hand with the development and use of dopants to the point that are now ubiquitous. Here, we give an overview of all important advances in the area of doping of org. semiconductors and their applications. We first review the relevant literature with particular focus on the phys. processes involved, discussing established mechanisms but also newly proposed theories. We then continue with a comprehensive summary of the most widely studied dopants to date, placing particular emphasis on the chem. strategies toward the synthesis of mols. with improved functionality. The processing routes toward doped org. films and the important doping-processing-nanostructure relationships, are also discussed. We conclude the review by highlighting how doping can enhance the operating characteristics of various org. devices.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXisFSgtLjJ&md5=1785c05b2620a3f751b0559c1865797a
  6. 6
    Li, J.; Duchemin, I.; Roscioni, O. M.; Friederich, P.; Anderson, M.; Da Como, E.; Kociok-Köhn, G.; Wenzel, W.; Zannoni, C.; Beljonne, D.; Blase, X.; D’Avino, G. Host dependence of the electron affinity of molecular dopants. Mater. Horiz. 2019, 6, 107– 114,  DOI: 10.1039/C8MH00921J
    Google Scholar
    6
    Host dependence of the electron affinity of molecular dopants
    Li, Jing; Duchemin, Ivan; Roscioni, Otello Maria; Friederich, Pascal; Anderson, Marie; Da Como, Enrico; Kociok-Kohn, Gabriele; Wenzel, Wolfgang; Zannoni, Claudio; Beljonne, David; Blase, Xavier; D'Avino, Gabriele
    Materials Horizons (2019), 6 (1), 107-114CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
    Charge carriers energetics is key in electron transfer processes such as those that enable the elec. doping of org. semiconductors. In this study, we take advantage of the quant. accuracy of embedded GW calcns. to perform a series of virtual expts. that allow measuring the electron affinity of p-type dopants in different host solids. Our calcns. show that the energy levels of a mol. impurity strongly depend on the host environment as a result of electrostatic intermol. interactions. In particular, the electron affinity of a dopant impurity in a given semiconductor is found to be up to 1 eV lower than that of the pure dopant crystal. This result questions the pertinence of the electron affinity measured for pure dopants in order to predict doping efficiency in a specific host. The role of the Coulomb electron-hole interaction for the dopant-to-semiconductor charge transfer and for the release of doping-induced charges is discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVejurzO&md5=93fc9d3dcb28a274fdda67ff8ce4a8ce
  7. 7
    Salzmann, I.; Heimel, G.; Oehzelt, M.; Winkler, S.; Koch, N. Molecular electrical doping of organic semiconductors: fundamental mechanisms and emerging dopant design rules. Acc. Chem. Res. 2016, 49, 370– 378,  DOI: 10.1021/acs.accounts.5b00438
    Google Scholar
    7
    Molecular Electrical Doping of Organic Semiconductors: Fundamental Mechanisms and Emerging Dopant Design Rules
    Salzmann, Ingo; Heimel, Georg; Oehzelt, Martin; Winkler, Stefanie; Koch, Norbert
    Accounts of Chemical Research (2016), 49 (3), 370-378CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
    A review. Today's information society depends on the authors' ability to controllably dope inorg. semiconductors, such as silicon, thereby tuning their elec. properties to application-specific demands. For optoelectronic devices, org. semiconductors, i.e., conjugated polymers and mols., have emerged as s superior alternative owing to the ease of tuning their optical gap through chem. variability and their potential for low-cost, large-area processing on flexible substrates. There, the potential of mol. elec. doping for improving the performance of, for example, org. light-emitting devices or org. solar cells has only recently been established. The doping efficiency, however, remains conspicuously low, highlighting the fact that the underlying mechanisms of mol. doping in org. semiconductors are only little understood compared with their inorg. counterparts. .Here, the authors review the broad range of phenomena obsd. upon molecularly doping org. semiconductors and identify two distinctly different scenarios: the pairwise formation of both org. semiconductor and dopant ions on one hand and the emergence of ground state charge transfer complexes between org. semiconductor and dopant through supramol. hybridization of their resp. frontier MOs on the other hand. Evidence for the occurrence of these two scenarios is subsequently discussed from the characteristic and strikingly different signatures of the individual species involved in the resp. doping processes in a variety of spectroscopic techniques. The crit. importance of a statistical view of doping, rather than a bimol. picture, is then highlighted by employing numerical simulations, which reveal one of the main differences between inorg. and org. semiconductors to be their resp. d. of electronic states and the doping induced changes thereof. Engineering the d. of states of doped org. semiconductors, the Fermi-Dirac occupation of which ultimately dets. the doping efficiency, thus emerges as key challenge. As a 1st step, the formation of charge transfer complexes is identified as being detrimental to the doping efficiency, which suggests sterically shielding the functional core of dopant mols. as an addnl. design rule to complement the requirement of low ionization energies or high electron affinities in efficient n-type or p-type dopants, resp. In an extended outlook, the authors finally argue that, to fully meet this challenge, an improved understanding is required of just how the admixt. of dopant mols. to org. semiconductors does affect the d. of states: compared with their inorg. counterparts, traps for charge carriers are omnipresent in org. semiconductors due to structural and chem. imperfections, and Coulomb attraction between ionized dopants and free charge carriers is typically stronger in org. semiconductors owing to their lower dielec. const. Nevertheless, encouraging progress is being made toward developing a unifying picture that captures the entire range of doping induced phenomena, from ion-pair to complex formation, in both conjugated polymers and mols. Once completed, such a picture will provide viable guidelines for synthetic and supramol. chem. that will enable further technol. advances in org. and hybrid org./inorg. devices.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFSjsrY%253D&md5=cc3b2014b0e798e89fa0f673aa011c7d
  8. 8
    Nell, B.; Ortstein, K.; Boltalina, O. V.; Vandewal, K. Influence of dopant–host energy level offset on thermoelectric properties of doped organic semiconductors. J. Phys. Chem. C 2018, 122, 11730– 11735,  DOI: 10.1021/acs.jpcc.8b03804
    Google Scholar
    8
    Influence of dopant-host energy level offset on thermoelectric properties of doped organic semiconductors
    Nell, Bernhard; Ortstein, Katrin; Boltalina, Olga V.; Vandewal, Koen
    Journal of Physical Chemistry C (2018), 122 (22), 11730-11735CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Increasing the amt. of charge carriers by mol. doping is important to improve the function of several org. electronic devices. In this work, the authors use highly fluorinated fullerene (C60F48) to p-type dope common amorphous mol. host materials. They observe a general relation between the material's elec. cond. and Seebeck coeff., both strongly depending on the energy level offset between the amorphous host and the dopant. This suggests that the doping efficiency at similar doping levels is mainly detd. by the electron transfer yield from host to dopant. Indeed, the dopant anion and host cation absorption strength correlate with the ionization energy (IE) of the host material. Host materials with an IE significantly below the electron affinity of the dopant yield the highest doping efficiency. Surprisingly, the doping efficiency reduces only by about 1 order of magnitude when the IE of the host material is increased by 0.55 eV, which they attribute to the disordered nature of the host materials.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptlyju7o%253D&md5=a665fe8b25ef7c15a9d82d8840e3752b
  9. 9
    Euvrard, J.; Revaux, A.; Bayle, P.-A.; Bardet, M.; Vuillaume, D.; Kahn, A. The formation of polymer-dopant aggregates as a possible origin of limited doping efficiency at high dopant concentration. Org. Electron. 2018, 53, 135– 140,  DOI: 10.1016/j.orgel.2017.11.020
    Google Scholar
    9
    The formation of polymer-dopant aggregates as a possible origin of limited doping efficiency at high dopant concentration
    Euvrard, Julie; Revaux, Amelie; Bayle, Pierre-Alain; Bardet, Michel; Vuillaume, Dominique; Kahn, Antoine
    Organic Electronics (2018), 53 (), 135-140CODEN: OERLAU; ISSN:1566-1199. (Elsevier B.V.)
    The polymer Poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b)dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno [3,4-b]thiophene-)-2-6-diyl] (PBDTTT-c) p-doped with the mol. dopant tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-COCF3)3) exhibits a decline in transport properties at high doping concns., which limits the performance attainable through org. semiconductor doping. SEM is used to correlate the evolution of hole cond. and hopping transport activation energy with the formation of aggregates in the layer. Transmission Electron Microscopy with energy-dispersive X-ray anal. along with liq.-state NMR expts. are carried out to det. the compn. of the aggregates. This study offers an explanation to the limited efficiency of doping at high dopant concns. and reinforces the need to increase doping efficiency in order to be able to reduce the dopant concn. and not neg. affect cond.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvV2qsLnF&md5=2ed763a7e6ecd26eff1f7ea43d3188b1
  10. 10
    Duong, D. T.; Wang, C.; Antono, E.; Toney, M. F.; Salleo, A. The chemical and structural origin of efficient p-type doping in P3HT. Org. Electron. 2013, 14, 1330– 1336,  DOI: 10.1016/j.orgel.2013.02.028
    Google Scholar
    10
    The chemical and structural origin of efficient p-type doping in P3HT
    Duong, Duc T.; Wang, Chenchen; Antono, Erin; Toney, Michael F.; Salleo, Alberto
    Organic Electronics (2013), 14 (5), 1330-1336CODEN: OERLAU; ISSN:1566-1199. (Elsevier B.V.)
    We investigate the chem. and structural properties of soln.-processed thin films of P3HT blended with p-type dopant F4TCNQ. The max. in-plane elec. cond. of doped films is obsd. at a molar doping fraction of 0.17, in agreement with the binding mechanism of F4TCNQ:P3HT complexes. Through the use of X-ray diffraction, a previously unreported cryst. phase is obsd. for P3HT films doped above a crit. threshold concn. This cryst. phase involves the incorporation of F4TCNQ mols. into ordered polymer regions and ultimately improves charge dissocn., leading to higher carrier d. in thin film. Finally, optical absorption and X-ray diffraction reveal that the chem. state of P3HT in soln. has a dramatic impact on the elec. and structural properties of the blended films.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXmt1Clsr8%253D&md5=dbe1ccee73b6e2e48528dfd1b29d2623
  11. 11
    Dixon, A. L.; Vezin, H.; Nguyen, T.-Q.; Reddy, G. N. M. Structural insights into Lewis acid- and F4TCNQ-doped conjugated polymers by solid-state magnetic resonance spectroscopy. Mater. Horiz. 2022, 9, 981– 990,  DOI: 10.1039/D1MH01574E
    Google Scholar
    11
    Structural insights into Lewis acid- and F4TCNQ-doped conjugated polymers by solid-state magnetic resonance spectroscopy
    Dixon, Alana L.; Vezin, Herve; Nguyen, Thuc-Quyen; Reddy, G. N. Manjunatha
    Materials Horizons (2022), 9 (3), 981-990CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
    Mol. doping strategies facilitate orders of magnitude enhancement in the charge carrier mobility of org. semiconductors (OSCs). Understanding the different doping mechanisms and mol.-level constraints on doping efficiency related to the material energy levels is crucial to develop versatile dopants for OSCs. Given the compositional and structural heterogeneities assocd. with OSC thin films, insight into dopant-polymer interactions by long-range techniques such as X-ray scattering and electron microscopy is exceedingly challenging to obtain. This study employs short-range probes, solid-state (ss) NMR and EPR spectroscopy, to resolve local structures and intermol. interactions between dopants such as F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), Lewis acid BCF (tris[pentafluorophenyl] borane) and Lewis base conjugated polymer, PCPDTBT (P4) (poly[2,6-(4,4-bis(2-hexadecyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]). Anal. of 1H and 13C ssNMR spectra of P4, P4 : F4TCNQ and P4 : BCF blends indicates that the addn. of dopants induces local structural changes in the P4 polymer, and causes paramagnetism-induced signal broadening and intensity losses. The hyperfine interactions in P4 : BCF and P4 : F4TCNQ are characterized by two-dimensional pulsed EPR spectroscopy. For P4 : F4TCNQ, 19F ssNMR anal. indicates that the F4TCNQ mols. are distributed and aggregated into different local chem. environments.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xislyruw%253D%253D&md5=2b5536c04d37fbe501f3fe322f9fbca7
  12. 12
    Kiefer, D.; Kroon, R.; Hofmann, A. I.; Sun, H.; Liu, X.; Giovannitti, A.; Stegerer, D.; Cano, A.; Hynynen, J.; Yu, L.; Zhang, Y.; Nai, D.; Harrelson, T. F.; Sommer, M.; Moulé, A. J.; Kemerink, M.; Marder, S. R.; McCulloch, I.; Fahlman, M.; Fabiano, S.; Müller, C. Double doping of conjugated polymers with monomer molecular dopants. Nat. Mater. 2019, 18, 149– 155,  DOI: 10.1038/s41563-018-0263-6
    Google Scholar
    12
    Double doping of conjugated polymers with monomer molecular dopants
    Kiefer, David; Kroon, Renee; Hofmann, Anna I.; Sun, Hengda; Liu, Xianjie; Giovannitti, Alexander; Stegerer, Dominik; Cano, Alexander; Hynynen, Jonna; Yu, Liyang; Zhang, Yadong; Nai, Dingqi; Harrelson, Thomas F.; Sommer, Michael; Moule, Adam J.; Kemerink, Martijn; Marder, Seth R.; McCulloch, Iain; Fahlman, Mats; Fabiano, Simone; Muller, Christian
    Nature Materials (2019), 18 (2), 149-155CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
    Mol. doping is a crucial tool for controlling the charge-carrier concn. in org. semiconductors. Each dopant mol. is commonly thought to give rise to only one polaron, leading to a max. of one donor:acceptor charge-transfer complex and hence an ionization efficiency of 100%. However, this theor. limit is rarely achieved because of incomplete charge transfer and the presence of unreacted dopant. Here, we establish that common p-dopants can in fact accept two electrons per mol. from conjugated polymers with a low ionization energy. Each dopant mol. participates in two charge-transfer events, leading to the formation of dopant dianions and an ionization efficiency of up to 200%. Furthermore, we show that the resulting integer charge-transfer complex can dissoc. with an efficiency of up to 170%. The concept of double doping introduced here may allow the dopant fraction required to optimize charge conduction to be halved.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmt1Oktbs%253D&md5=f3b09a943b9edecf64ef493a17f35ba3
  13. 13
    Goel, M.; Siegert, M.; Krauss, G.; Mohanraj, J.; Hochgesang, A.; Heinrich, D. C.; Fried, M.; Pflaum, J.; Thelakkat, M. HOMO–HOMO electron transfer: An elegant strategy for p-type doping of polymer semiconductors toward thermoelectric applications. Adv. Mater. 2020, 32, 2003596  DOI: 10.1002/adma.202003596
    Google Scholar
    13
    HOMO-HOMO Electron Transfer: An Elegant Strategy for p-Type Doping of Polymer Semiconductors toward Thermoelectric Applications
    Goel, Mahima; Siegert, Marie; Krauss, Gert; Mohanraj, John; Hochgesang, Adrian; Heinrich, David C.; Fried, Martina; Pflaum, Jens; Thelakkat, Mukundan
    Advanced Materials (Weinheim, Germany) (2020), 32 (43), 2003596CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Unlike the conventional p-doping of org. semiconductors (OSCs) using acceptors, here, an efficient doping concept for diketopyrrolopyrrole-based polymer PDPP[T]2-EDOT (OSC-1) is presented using an oxidized p-type semiconductor, Spiro-OMeTAD(TFSI)2 (OSC-2), exploiting electron transfer from HOMOOSC-1 to HOMOOSC-2. A shift of work function toward the HOMOOSC-1 upon doping is confirmed by UPS. Detailed XPS and UV-vis-NIR absorption studies confirm HOMOOSC-1 to HOMOOSC-2 electron transfer. The redn. products of Spiro-OMeTAD(TFSI)2 to Spiro-OMeTAD(TFSI)2 and Spiro-OMeTAD is also confirmed and their relative amts. in doped samples is detd. Mott-Schottky anal. shows two orders of magnitude increase in free charge carrier d. and one order of magnitude increase in the charge carrier mobility. The cond. increases considerably by four orders of magnitude to a max. of 10 S m-1 for a very low doping ratio of 8 mol%. The doped polymer films exhibit high thermal and ambient stability resulting in a max. power factor of 0.07μW m-1 K-2 at a Seebeck coeff. of 140μV K-1 for a very low doping ratio of 4 mol%. Also, the concept of HOMOOSC-1 to HOMOOSC-2 electron transfer is a highly efficient, stable and generic way to p-dope other conjugated polymers.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhvVKgtrnI&md5=876167efc0f58974212d37ef0110fa16
  14. 14
    Krauss, G.; Hochgesang, A.; Mohanraj, J.; Thelakkat, M. Highly Efficient Doping of Conjugated Polymers Using Multielectron Acceptor Salts. Macromol. Rapid Commun. 2021, 42, 2100443  DOI: 10.1002/marc.202100443
    Google Scholar
    14
    Highly Efficient Doping of Conjugated Polymers Using Multielectron Acceptor Salts
    Krauss, Gert; Hochgesang, Adrian; Mohanraj, John; Thelakkat, Mukundan
    Macromolecular Rapid Communications (2021), 42 (22), 2100443CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Chem. doping is a vital tool for tuning electronic properties of conjugated polymers. Most single electron acceptors used for p-doping necessitate high dopant concns. to achieve good elec. cond. However, high-molar doping ratios hamper doping efficiency. Here a new concept of using multielectron acceptor (MEA) salts as dopants for conjugated polymers is presented. Two novel MEA salts are synthesized and their doping efficiency to toward two polymers differing in their dielec. properties are compared with two single electron acceptors such as NOPF6 and magic blue. Cutting-edge methods such as UPS/XPS, impedance spectroscopy, and d. of states anal. in addn. to UV-vis-NIR absorption, spectroelectrochem., and Raman spectroscopy methods are used to characterize the doped systems. The tetracation salt improves the cond. by two orders of magnitude and quadruples the charge carrier concn. compared to single electron acceptors for the same molar ratio. The differences in charge carrier d. and activation energy on doping are delineated. Further, a strong dependency of the carrier release on the polymer polarity is obsd. High carrier densities at reduced dopant loadings and improved doping efficacies using MEA dopants offer a highly efficient doping strategy for conjugated polymers.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitlWntL7N&md5=5705cbc1e4040e4d8056c51a0860a43c
  15. 15
    Paniagua, S. A.; Baltazar, J.; Sojoudi, H.; Mohapatra, S. K.; Zhang, S.; Henderson, C. L.; Graham, S.; Barlow, S.; Marder, S. R. Production of heavily n- and p-doped CVD graphene with solution-processed redox-active metal–organic species. Mater. Horiz. 2014, 1, 111– 115,  DOI: 10.1039/C3MH00035D
    Google Scholar
    15
    Production of heavily n- and p-doped CVD graphene with solution-processed redox-active metal-organic species
    Paniagua, Sergio A.; Baltazar, Jose; Sojoudi, Hossein; Mohapatra, Swagat K.; Zhang, Siyuan; Henderson, Clifford L.; Graham, Samuel; Barlow, Stephen; Marder, Seth R.
    Materials Horizons (2014), 1 (1), 111-115CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
    CVD graphene has been n- and p-doped using redox-active, soln.-processed metal-org. complexes. Elec. measurements, photoemission spectroscopies, and Raman spectroscopy were used to characterize the doped films and give insights into the changes. The work function decreased by as much as 1.3 eV with the n-dopant, with contributions from electron transfer and surface dipole, and the cond. significantly increased.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVShsbrO&md5=04a92aad248993ed5ec2c436060abd60
  16. 16
    Mohapatra, S. K.; Zhang, Y.; Sandhu, B.; Fonari, M. S.; Timofeeva, T. V.; Marder, S. R.; Barlow, S. Synthesis, characterization, and crystal structures of molybdenum complexes of unsymmetrical electron-poor dithiolene ligands. Polyhedron 2016, 116, 88– 95,  DOI: 10.1016/j.poly.2016.04.025
    Google Scholar
    16
    Synthesis, characterization, and crystal structures of molybdenum complexes of unsymmetrical electron-poor dithiolene ligands
    Mohapatra, Swagat K.; Zhang, Yadong; Sandhu, Bhupinder; Fonari, Marina S.; Timofeeva, Tatiana V.; Marder, Seth R.; Barlow, Stephen
    Polyhedron (2016), 116 (), 88-95CODEN: PLYHDE; ISSN:0277-5387. (Elsevier Ltd.)
    Mo(S2C2(CF3)2)3, 1a, has proven a useful p-dopant in org. electronics. To develop more sol. p-dopants, MoS2-9 was treated with alkynes CF3CCCO2Me and CF3CCCOCF3 to give the dianions of the corresponding tris(dithiolene) complexes, 1b2- and 1c2-, resp., which were then oxidized to neutral molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene], 1b, and molybdenum tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene], 1c, using NO+PF-6. The crystal structures of (NEt+4)21b2-, (NEt+4)21c2-, and neutral 1c have been detd. In all three cases, the metal coordination is approx. trigonal prismatic and the major isomer is cis (approx. C3v). The structure of 1b2- is distorted by a twist towards pseudo-octahedral coordination similar to that seen in structures of 1a2- and Mo(S2C2(CO2Me)2)2-3, 1d2-, salts, and that of 1c exhibits marked folds between the planes formed by the ligand atoms and those formed by the Mo and coordinated S atoms, similar to those seen in the structure of 1a. On the other hand, the metal dithiolene core of 1c2- is essentially undistorted from C3v symmetry. The oxidant strength of the neutral mols. increases in the order 1d < 1b < 1a < 1c, with the potentials ranging from -0.02 to +0.39 V vs. the ferrocenium/ferrocene couple.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XmvFyjtLw%253D&md5=9d72fafaa35554b0ab8ea2fe669913e1
  17. 17
    Qi, Y.; Sajoto, T.; Barlow, S.; Kim, E.-G.; Brédas, J.-L.; Marder, S. R.; Kahn, A. Use of a High Electron-Affinity Molybdenum Dithiolene Complex to p-Dope Hole-Transport Layers. J. Am. Chem. Soc. 2009, 131, 12530– 12531,  DOI: 10.1021/ja904939g
    Google Scholar
    17
    Use of a High Electron-Affinity Molybdenum Dithiolene Complex to p-Dope Hole-Transport Layers
    Qi, Yabing; Sajoto, Tissa; Barlow, Stephen; Kim, Eung-Gun; Bredas, Jean-Luc; Marder, Seth R.; Kahn, Antoine
    Journal of the American Chemical Society (2009), 131 (35), 12530-12531CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Exptl. and theor. results are presented on the electronic structure of molybdenum tris[1,2-bis(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd)3), a high electron-affinity organometallic complex that constitutes a promising candidate as a p-dopant for org. mol. semiconductors. The electron affinity of the compd., detd. via inverse photoemission spectroscopy, is 5.6 eV, which is 0.4 eV larger than that of the commonly used p-dopant F4-TCNQ. The LUMO level of Mo(tfd)3 is calcd. to be delocalized over the whole mol., which is expected to lead to low pinning potential. Efficient p-doping of a std. hole transport material (α-NPD) is demonstrated via measurements of Fermi level shifts and enhanced cond. in α-NPD:1% Mo(tfd)3. Rutherford backscattering measurements show good stability of the three-dimensional Mo(tfd)3 mol. in the host matrix with respect to diffusion.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXpvV2nt70%253D&md5=5fac0de719f3555a67f9afc195facaca
  18. 18
    Hynynen, J.; Järsvall, E.; Kroon, R.; Zhang, Y.; Barlow, S.; Marder, S. R.; Kemerink, M.; Lund, A.; Müller, C. Enhanced thermoelectric power factor of tensile drawn poly(3-hexylthiophene). ACS Macro Lett. 2019, 8, 70– 76,  DOI: 10.1021/acsmacrolett.8b00820
    Google Scholar
    18
    Enhanced Thermoelectric Power Factor of Tensile Drawn Poly(3-hexylthiophene)
    Hynynen, Jonna; Jaersvall, Emmy; Kroon, Renee; Zhang, Yadong; Barlow, Stephen; Marder, Seth R.; Kemerink, Martijn; Lund, Anja; Muller, Christian
    ACS Macro Letters (2019), 8 (1), 70-76CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
    The thermoelec. power factor of a broad range of org. semiconductors scales with their elec. cond. according to a widely obeyed power law, and therefore, strategies that permit this empirical trend to be surpassed are highly sought after. Here, tensile drawing of the conjugated polymer, poly(3-hexylthiophene), (P3HT), is employed to create free-standing films with a high degree of uniaxial alignment. Along the direction of orientation, sequential doping with a molybdenum tris(dithiolene) complex leads to a 5-fold enhancement of the power factor beyond the predicted value, reaching up to 16 μW m-1 K-2 for a cond. of about 13 S cm-1. Neither stretching nor doping affect the glass transition temp. of P3HT, giving rise to robust free-standing materials that are of interest for the design of flexible thermoelec. devices.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisFyrsr7K&md5=33ea2ed7251d1cd45b6f41be95a700fa
  19. 19
    Untilova, V.; Hynynen, J.; Hofmann, A. I.; Scheunemann, D.; Zhang, Y.; Barlow, S.; Kemerink, M.; Marder, S. R.; Biniek, L.; Müller, C.; Brinkmann, M. High thermoelectric power factor of poly(3-hexylthiophene) through in-plane alignment and doping with a molybdenum dithiolene complex. Macromolecules 2020, 53, 6314– 6321,  DOI: 10.1021/acs.macromol.0c01223
    Google Scholar
    19
    High Thermoelectric Power Factor of Poly(3-hexylthiophene) through In-Plane Alignment and Doping with a Molybdenum Dithiolene Complex
    Untilova, Viktoriia; Hynynen, Jonna; Hofmann, Anna I.; Scheunemann, Dorothea; Zhang, Yadong; Barlow, Stephen; Kemerink, Martijn; Marder, Seth R.; Biniek, Laure; Muller, Christian; Brinkmann, Martin
    Macromolecules (Washington, DC, United States) (2020), 53 (15), 6314-6321CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Here we report a record thermoelec. power factor of up to 160μW m-1 K-2 for the conjugated polymer poly(3-hexylthiophene) (P3HT). This result is achieved through the combination of high-temp. rubbing of thin films together with the use of a large molybdenum dithiolene p-dopant with a high electron affinity. Comparison of the UV-vis-NIR spectra of the chem. doped samples to electrochem. oxidized material reveals an oxidn. level of 10%, i.e. one polaron for every 10 repeat units. The high power factor arises due to an increase in the charge-carrier mobility and hence elec. cond. along the rubbing direction. We conclude that P3HT, with its facile synthesis and outstanding processability, should not be ruled out as a potential thermoelec. material.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhsVajtLfM&md5=82504474af50f8b0649799ecd43821f9
  20. 20
    Yamashita, Y.; Tsurumi, J.; Kurosawa, T.; Ueji, K.; Tsuneda, Y.; Kohno, S.; Kempe, H.; Kumagai, S.; Okamoto, T.; Takeya, J.; Watanabe, S. Supramolecular cocrystals built through redox-triggered ion intercalation in π-conjugated polymers. Commun. Mater. 2021, 2, 45  DOI: 10.1038/s43246-021-00148-9
    Google Scholar
    20
    Supramolecular cocrystals built through redox-triggered ion intercalation in π-conjugated polymers
    Yamashita, Yu; Tsurumi, Junto; Kurosawa, Tadanori; Ueji, Kan; Tsuneda, Yukina; Kohno, Shinya; Kempe, Hideto; Kumagai, Shohei; Okamoto, Toshihiro; Takeya, Jun; Watanabe, Shun
    Communications Materials (2021), 2 (1), 45CODEN: CMOAGE; ISSN:2662-4443. (Nature Portfolio)
    Self-organization in π-conjugated polymers gives rise to a highly ordered lamellar structure, in which inter-chain stacking spontaneously forms two-dimensional conjugated sheets. This multi-layer stacked nature of semicryst. polymers allows the inclusion of various functional mols. In particular, redox-triggered ion-intercalation is an ideal system for mol. doping, for which extremely high charge carrier d. has been achieved. Here, we conducted a detailed structural anal. and electron d. simulation to pinpoint exactly where the guest dopants are located periodically in the void space in a polymer's lamellae. Our findings are indicative of an intercalation compd. of layered polymers and a guest intercalant. We show that a homogeneous cocrystal structure can be realized throughout the host polymer medium, which is proved by the observation of coherent carrier transport. The intercalation cocrystal nature gives the best achievable doping level in semicryst. polymers and excellent environmental stability. These findings should open up possibilities for tuning the collective dynamics of functional mols. through intercalation phenomena.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XotVCkt78%253D&md5=45655daf5fa42837638a5b8f23d4865e
  21. 21
    Jacobs, I. E.; Lin, Y.; Huang, Y.; Ren, X.; Simatos, D.; Chen, C.; Tjhe, D.; Statz, M.; Lai, L.; Finn, P. A.; Neal, W. G.; D’Avino, G.; Lemaur, V.; Fratini, S.; Beljonne, D.; Strzalka, J.; Nielsen, C. B.; Barlow, S.; Marder, S. R.; McCulloch, I.; Sirringhaus, H. High-efficiency ion-exchange doping of conducting polymers. Adv. Mater. 2021, 2102988  DOI: 10.1002/adma.202102988
    Google Scholar
    There is no corresponding record for this reference.
  22. 22
    Euvrard, J.; Revaux, A.; Nobre, S. S.; Kahn, A.; Vuillaume, D. Toward a better understanding of the doping mechanism involved in Mo(tfd-COCF3)3 doped PBDTTT-c. J. Appl. Phys. 2018, 123, 225501  DOI: 10.1063/1.5029810
    Google Scholar
    22
    Toward a better understanding of the doping mechanism involved in Mo(tfd-COCF3)3 doped PBDTTT-c
    Euvrard, J.; Revaux, A.; Nobre, S. S.; Kahn, A.; Vuillaume, D.
    Journal of Applied Physics (Melville, NY, United States) (2018), 123 (22), 225501/1-225501/10CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
    The authors aim to improve the understanding of the doping mechanism involved in the polymer poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b')dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno [3,4-b]thiophene-)-2-6-diyl)]] (PBDTTT-c) doped with tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] [Mo(tfd-COCF3)3]. The authors follow the evolution of the hole d. with dopant concn. to highlight the limits of org. semiconductor doping. To enable the use of doping to enhance the performance of org. electronic devices, doping efficiency must be understood and improved. The authors report here a study using complementary optical and elec. characterization techniques, which sheds some light on the origin of this limited doping efficiency at a high dopant concn. Two doping mechanisms are considered, the direct charge transfer and the charge transfer complex. The validity of the model involved as well as its impact on the doping efficiency are discussed. (c) 2018 American Institute of Physics.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFemtbrK&md5=dd28ddbea73d60f054d11d1b97a7e22c
  23. 23
    Nunes Domschke, T.; Bardagot, O.; Benayad, A.; Demadrille, R.; Carella, A.; Clerc, R.; Pereira, A. Unraveling the mechanism behind air instability in thin semiconducting polymer layers p-doped with molybdenum dithiolene complexes. Synth. Met. 2020, 260, 116251  DOI: 10.1016/j.synthmet.2019.116251
    Google Scholar
    23
    Unraveling the mechanism behind air instability in thin semiconducting polymer layers p-doped with molybdenum dithiolene complexes
    Nunes Domschke, Tamara; Bardagot, Olivier; Benayad, Anass; Demadrille, Renaud; Carella, Alexandre; Clerc, Raphael; Pereira, Alexandre
    Synthetic Metals (2020), 260 (), 116251CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier B.V.)
    Doping efficiency and stability are crucial requirements for the integration of doped org. semiconductors in optoelectronic devices. This work presents a detailed exptl. study on the air stability of p-doped systems based on a low-bandgap polymer, poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b')dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2-6-diyl] (PBDTTT-c) doped with a strong mol. p-dopant, i.e. molybdenum tris[1-(trifluoroethanoyl)-2-(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd-COCF3)3). The elec. cond. and the optical absorption are measured for different dopant concns. in argon atm., and their variations monitored as a function of the air exposure time. The results indicate a clear instability under ambient air related to a dedoping process, which is particularly pronounced in ultra-thin (< 50 nm) doped layers. By evaluating the stability of the p-doped polymer layers under different atmospheres (ambient air, anhyd. air and argon), the detrimental impact of moisture and/or O2(H20)n complexes is highlighted. XPS revealed that the p-doping instability in ambient air can be assigned to changes in the oxidn. state of the metallic center as well as to an intrinsic degrdn. of the dopant mol. This study unravels an important degrdn. mechanism with this class of dopants that should be taken under consideration and solved for future integration of ultrathin p-doped layers in printed electronic devices.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXisVSrsL7P&md5=2d2ba5075414c0ec3197862e9d63c632
  24. 24
    Barrière, F.; Camire, N.; Geiger, W. E.; Mueller-Westerhoff, U. T.; Sanders, R. Use of Medium Effects to Tune the ΔE1/2 Values of Bimetallic and Oligometallic Compounds. J. Am. Chem. Soc. 2002, 124, 7262– 7263,  DOI: 10.1021/ja020309d
    Google Scholar
    24
    Use of Medium Effects to Tune the ΔE1/2 Values of Bimetallic and Oligometallic Compounds
    Barriere, Frederic; Camire, Nicole; Geiger, William E.; Mueller-Westerhoff, Ulrich T.; Sanders, Richard
    Journal of the American Chemical Society (2002), 124 (25), 7262-7263CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The redox potentials of bis(fulvalene)dinickel (1), and the tetrakis(ferrocenyl)nickel dithiolene complex (2) were measured in a variety of nonaq. electrolytes. The difference in E1/2 values of the two successive 1-electron oxidns. of 1 (i.e., ΔE1/2 values) increased from a low of 212 mV in anisole/[NBu4]Cl to a high of 850 mV in CH2Cl2-Na[B(C6H3(CF3)2)4], reflecting an increase of over 1010 in the comproportionation const. (Kcomp = [1+]2/[1][12+]). Six reversible 1-electron processes are possible for compd. 2, the four oxidns. arising from the ferrocenyl substituents, and the two redns. arising from the Ni dithiolene moiety. The E1/2 spreads of the four oxidn. waves and the two redn. waves are both highly sensitive to medium effects. For both 1 and 2, the largest ΔE1/2 values for cationic products are found in solvents of low polarity and donor strength contg. electrolyte salts having large anions and small cations. Conversely, the smallest ΔE1/2 values for anionic products are found under these conditions, culminating in the observation of a single two-electron redn. wave for 2/22- in CH2Cl2-Na[B(C6H3(CF3)2)4]. A combination of solvation and ion-pairing effects must be considered, and may be used to advantage, when using ΔE1/2 values as a measure of electronic interactions between redox centers in compds. contg. two or more electron-transfer sites.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XktVKjtrk%253D&md5=7dccf3082653716809854d440bb204c1
  25. 25
    Zokaei, S.; Kroon, R.; Gladisch, J.; Paulsen, B. D.; Sohn, W.; Hofmann, A. I.; Persson, G.; Stamm, A.; Syrén, P.-O.; Olsson, E.; Rivnay, J.; Stavrinidou, E.; Lund, A.; Müller, C. Toughening of a Soft Polar Polythiophene through Copolymerization with Hard Urethane Segments. Adv. Sci. 2021, 8, 2002778  DOI: 10.1002/advs.202002778
    Google Scholar
    25
    Toughening of a Soft Polar Polythiophene through Copolymerization with Hard Urethane Segments
    Zokaei, Sepideh; Kroon, Renee; Gladisch, Johannes; Paulsen, Bryan D.; Sohn, Wonil; Hofmann, Anna I.; Persson, Gustav; Stamm, Arne; Syren, Per-Olof; Olsson, Eva; Rivnay, Jonathan; Stavrinidou, Eleni; Lund, Anja; Mueller, Christian
    Advanced Science (Weinheim, Germany) (2021), 8 (2), 2002778CODEN: ASDCCF; ISSN:2198-3844. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temp. and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported. The mol. design is contrary to that of other semiconductor-insulator copolymers, which typically combine a soft nonconjugated spacer with hard conjugated segments. Copolymn. of polar polythiophenes and urethane segments results in a ductile material that can be used as a free-standing solid. The copolymer displays a storage modulus of 25 MPa at room temp., elongation at break of 95%, and a reduced degree of swelling due to hydrogen bonding. Both chem. doping and electrochem. oxidn. reveal that the introduction of urethane segments does not unduly reduce the hole charge-carrier mobility and ability to take up charge. Further, stable operation is obsd. when the copolymer is used as the active layer of org. electrochem. transistors.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXps1yls7s%253D&md5=0b476b3c0f3193fc4793e8372f53b14e
  26. 26
    Wang, E.; Hou, L.; Wang, Z.; Hellström, S.; Zhang, F.; Inganäs, O.; Andersson, M. R. An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells. Adv. Mater. 2010, 22, 5240– 5244,  DOI: 10.1002/adma.201002225
    Google Scholar
    26
    An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells
    Wang, Ergang; Hou, Lintao; Wang, Zhongqiang; Hellstroem, Stefan; Zhang, Fengling; Inganaes, Olle; Andersson, Mats R.
    Advanced Materials (Weinheim, Germany) (2010), 22 (46), 5240-5244CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The authors report an easily synthesized donor-acceptor (D-A) type of low bandgap polymer based on thiophene and quinoxaline named poly[2,3-bis(3-octyloxyphenyl)quinoxaline-5,8-diyl-thiophene-2,5-diyl] (TQ1) and explore its application in polymer solar cells. This polymer structure and its optical properties have previously been disclosed by Yamamoto et al.(l9). Recently, several similar polymers with different side chains were synthesized with low mol. wts., showing poor photovoltaic performance. In this paper, the authors modify the synthesis of the monomers and also TQ1 and investigate its optical, electrochem. and photovoltaic properties. After early optimization of the prepn. of the solar cells, a max. power point (MPP) up to 6 mW/m2 was achieved with a high VOC of ca. 0.9 V from a blend of TQ1 and [70]PCBM under illumination from an air mass 1.5 global (AM 1.5G) solar simulator (100 mW/cm2).
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsFClurfP&md5=f2eb255e12121eb15db2986eb7665859
  27. 27
    Kroon, R.; Gehlhaar, R.; Steckler, T. T.; Henriksson, P.; Müller, C.; Bergqvist, J.; Hadipour, A.; Heremans, P.; Andersson, M. R. New quinoxaline and pyridopyrazine-based polymers for solution-processable photovoltaics. Sol. Energy Mater. Sol. Cells 2012, 105, 280– 286,  DOI: 10.1016/j.solmat.2012.06.029
    Google Scholar
    27
    New quinoxaline and pyridopyrazine-based polymers for solution-processable photovoltaics
    Kroon, Renee; Gehlhaar, Robert; Steckler, Timothy T.; Henriksson, Patrik; Mueller, Christian; Bergqvist, Jonas; Hadipour, Afshin; Heremans, Paul; Andersson, Mats R.
    Solar Energy Materials & Solar Cells (2012), 105 (), 280-286CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)
    The recently published quinoxaline/thiophene-based polymer TQ1 has been modified on its acceptor unit, either altering the acceptor strength by incorporating a pyridopyrazine, substitution of the acceptor-hydrogens by fluorine, or substitution of the alkoxy side chain by alkyl. The changes in phys., electronic and device properties are discussed. For the polymers incorporating the stronger acceptors a decreased performance is found, where in both cases the current in the devices is compromised. Incorporation of the pyridopyrazine-based acceptor seems to result in more severe or addnl. loss mechanisms compared to the polymer that incorporates the fluorine atoms. A similar performing material is obtained when changing the alkoxy side chain in TQ1 to an alkyl, where the solar cell performance is mainly improved on the fill factor. It is demonstrated that the std. TQ1 structure is easily modified in a no. of ways, showing the versatility and robustness of the std. TQ1 structure and synthesis.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFWht7vO&md5=fb41d26ced86b73565aead4e53aaa201
  28. 28
    Arvind, M.; Tait, C. E.; Guerrini, M.; Krumland, J.; Valencia, A. M.; Cocchi, C.; Mansour, A. E.; Koch, N.; Barlow, S.; Marder, S. R.; Behrends, J.; Neher, D. Quantitative Analysis of Doping-Induced Polarons and Charge-Transfer Complexes of Poly(3-hexylthiophene) in Solution. J. Phys. Chem. B 2020, 124, 7694– 7708,  DOI: 10.1021/acs.jpcb.0c03517
    Google Scholar
    28
    Quantitative Analysis of Doping-Induced Polarons and Charge-Transfer Complexes of Poly(3-hexylthiophene) in Solution
    Arvind, Malavika; Tait, Claudia E.; Guerrini, Michele; Krumland, Jannis; Valencia, Ana M.; Cocchi, Caterina; Mansour, Ahmed E.; Koch, Norbert; Barlow, Stephen; Marder, Seth R.; Behrends, Jan; Neher, Dieter
    Journal of Physical Chemistry B (2020), 124 (35), 7694-7708CODEN: JPCBFK; ISSN:1520-5207. (American Chemical Society)
    The mechanism and the nature of the species formed by mol. doping of the model polymer poly(3-hexylthiophene) (P3HT) in its regioregular (rre-) and regiorandom (rra-) forms in soln. are investigated for three different dopants: the prototypical π-electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), the strong Lewis acid tris(pentafluorophenyl)borane (BCF), and the strongly oxidizing complex molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-CO2Me)3). In a combined optical and ESR study, we show that the doping of rreP3HT in soln. occurs by integer charge transfer, resulting in formation of P3HT radical cations (polarons) for all of the dopants considered here. Remarkably, despite the different chem. nature of the dopants and dopant-polymer interaction, the formed polarons exhibit essentially identical optical absorption spectra. The situation is very different for the doping of rraP3HT, where we observe formation of a charge-transfer complex with F4TCNQ and of a "localized" P3HT polaron on nonaggregated chains upon doping with BCF, while there is no indication of dopant-induced species in the case of Mo(tfd-CO2Me)3. We est. the ionization efficiency of the resp. dopants for the two polymers in soln. and report the molar extinction coeff. spectra of the three different species. Finally, we observe increased spin delocalization in regioregular compared to regiorandom P3HT by electron nuclear double resonance, suggesting that the ability of the charge to delocalize on aggregates of planarized polymer backbones plays a significant role in detg. the doping mechanism.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1alsLnO&md5=b1d21484bf514780f2a2d9c63a6b952f
  29. 29
    Fekl, U.; Sarkar, B.; Kaim, W.; Zimmer-De Iuliis, M.; Nguyen, N. Tuning of the Spin Distribution between Ligand- and Metal-Based Spin: Electron Paramagnetic Resonance of Mixed-Ligand Molybdenum Tris(dithiolene) Complex Anions. Inorg. Chem. 2011, 50, 8685– 8687,  DOI: 10.1021/ic201047k
    Google Scholar
    29
    Tuning of the Spin Distribution between Ligand- and Metal-Based Spin: Electron Paramagnetic Resonance of Mixed-Ligand Molybdenum Tris(dithiolene) Complex Anions
    Fekl, Ulrich; Sarkar, Biprajit; Kaim, Wolfgang; Zimmer-De Iuliis, Marco; Nguyen, Neilson
    Inorganic Chemistry (2011), 50 (18), 8685-8687CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    ESR spectra of homoleptic and mixed-ligand molybdenum tris(dithiolene) complex anions [Mo(tfd)m(bdt)n]- (n + m = 3; bdt = S2C6H4; tfd = S2C2(CF3)2) showed that the spin d. had mixed metal-ligand character with more ligand-based spin for [Mo(tfd)3]- and a higher degree of metal-based spin for [Mo(bdt)3]-. The magnitude of the isotropic 95,97Mo hyperfine interaction increased continuously, by a factor of 2.5, on going from the former to the latter. The mixed complexes were in between, and the metal character of the spin increased with the bdt content. The expts. were corroborated by d. functional theory computations, which reproduced this steady increase in metal-based character.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGnu7rO&md5=137ddc2c26aedb716a36d7d5cd5d4dcd
  30. 30
    Davison, A.; Edelstein, N.; Holm, R. H.; Maki, A. H. Synthetic and Electron Spin Resonance Studies of Six-Coordinate Complexes Related by Electron-Transfer Reactions. J. Am. Chem. Soc. 1964, 86, 2799– 2805,  DOI: 10.1021/ja01068a010
    Google Scholar
    30
    Synthetic and electron spin resonance (E.S.R.) studies of six-coordinate complexes related by electron-transfer reactions
    Davison, A.; Edelstein, N.; Holm, R. H.; Maki, A. H.
    Journal of the American Chemical Society (1964), 86 (14), 2799-805CODEN: JACSAT; ISSN:0002-7863.
    A new series of 6-coordinate complexes of the general type [MS6-C6R6]2 with R = CF3 (M = Cr, Mo, W, z = 0, 1-, 2-) and R = CN(M = Cr, V, z = 2-; M = Cr; z = 3-)was prepd. These complexes are similar to related bis complexes in that they contain metals stabilized in several different oxidn. states, and complexes of given R and M can be interconverted by simple oxidn.-redn. reactions. The syntheses of all compds. are described in detail, and chem. stabilities are discussed in terms of polarog. half-wave potentials. The results of magnetic susceptibility, E.S.R., and IR studies are discussed. E.S.R. results show the presence of a strong trigonal component in the octahedral ligand field in complexes with a doublet ground state, and are not in agreement with the conventional d01 or (a1*)1 ground state. Probable electronic structures of these complexes are discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF2cXkt12msrs%253D&md5=55df56f9f6234ad1b2696b4e8a0390aa
  31. 31
    Tenderholt, A. L.; Szilagyi, R. K.; Holm, R. H.; Hodgson, K. O.; Hedman, B.; Solomon, E. I. Electronic Control of the “Bailar Twist” in Formally d0-d2 Molybdenum Tris(dithiolene) Complexes: A Sulfur K-edge X-ray Absorption Spectroscopy and Density Functional Theory Study. Inorg. Chem. 2008, 47, 6382– 6392,  DOI: 10.1021/ic800494h
    Google Scholar
    31
    Electronic Control of the "Bailar Twist" in Formally d-d2 Molybdenum Tris(dithiolene) Complexes: A Sulfur K-edge X-ray Absorption Spectroscopy and Density Functional Theory Study
    Tenderholt, Adam L.; Szilagyi, Robert K.; Holm, Richard H.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.
    Inorganic Chemistry (2008), 47 (14), 6382-6392CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    Sulfur K-edge X-ray absorption spectroscopy (XAS) and d. functional theory (DFT-GGA) calcns. have been used to det. the electronic structures of a series of Mo tris(dithiolene) complexes, [Mo(mdt)3]z (where mdt = 1,2-dimethylethene-1,2-dithiolate(2-) and z = 2-, 1-, 0), with near trigonal-prismatic geometries (D3h symmetry). These results show that the formally MoIV, MoV, and MoVI complexes actually have a (dz2)2 configuration, i.e., remain effectively MoIV despite oxidn. Comparisons with the XAS data of another set of Mo tris(dithiolene) complexes, [Mo(tbbdt)3]z (where tbbdt = 3,5-di-tert-butylbenzene-1,2-dithiolate(2-) and z = 1-, 0), show that both neutral complexes, [Mo(mdt)3] and [Mo(tbbdt)3], have similar electronic structures while the monoanions do not. Calcns. reveal that the "Bailar twist" present in the crystal structure of [Mo(tbbdt)3]1- (D3 symmetry) but not [Mo(mdt)3]1- (D3h symmetry) is controlled by electronic factors which arise from bonding differences between the mdt and tbbdt ligands. In the former, CI between the Mo dz2 and a deeper energy, occupied ligand orbital, which occurs in D3 symmetry, destabilizes the Mo dz2 to above another ligand orbital which is half-occupied in the D3h [Mo(mdt)3]1- complex. This leads to a metal d1 configuration with no ligand holes (i.e., d1[L3]0h) for [Mo(tbbdt)3]1- rather than the metal d2 configuration with one ligand hole (i.e., d2[L3]1h) for [Mo(mdt)3]1-. Thus, the Bailar twist obsd. in some metal tris(dithiolene) complexes is the result of CI between metal and ligand orbitals and can be probed exptl. by S K-edge XAS.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXms1agtrg%253D&md5=fb2b3c2e3d4d4a81799dde053635c05a
  32. 32
    Connelly, N. G.; Geiger, W. E. Chemical Redox Agents for Organometallic Chemistry. Chem. Rev. 1996, 96, 877– 910,  DOI: 10.1021/cr940053x
    Google Scholar
    32
    Chemical Redox Agents for Organometallic Chemistry
    Connelly, Neil G.; Geiger, William E.
    Chemical Reviews (Washington, D. C.) (1996), 96 (2), 877-910CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review, with >461 refs., showing how one-electron oxidants and reductants have been used in preparative chem. (incorporating both synthetic applications and generation of species for in situ characterization) in nonaq. solns., the usual media for organometallic ET reactions. The authors do not treat photochem.-generated reducing agents which, although generally transient species, may have advantages in some applications.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XhsVGhu7Y%253D&md5=205b204d99818aded3c41067d4bf85e3
  33. 33
    Hofmann, A. I.; Kroon, R.; Zokaei, S.; Järsvall, E.; Malacrida, C.; Ludwigs, S.; Biskup, T.; Müller, C. Chemical doping of conjugated polymers with the strong oxidant magic blue. Adv. Electron. Mater. 2020, 6, 2000249  DOI: 10.1002/aelm.202000249
    Google Scholar
    33
    Chemical Doping of Conjugated Polymers with the Strong Oxidant Magic Blue
    Hofmann, Anna I.; Kroon, Renee; Zokaei, Sepideh; Jaersvall, Emmy; Malacrida, Claudia; Ludwigs, Sabine; Biskup, Till; Mueller, Christian
    Advanced Electronic Materials (2020), 6 (8), 2000249CODEN: AEMDBW; ISSN:2199-160X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Mol. doping of org. semiconductors is a powerful tool for the optimization of org. electronic devices and org. thermoelec. materials. However, there are few redox dopants that have a sufficiently high electron affinity to allow the doping of conjugated polymers with an ionization energy of more than 5.3 eV. Here, p-doping of a broad palette of conjugated polymers with high ionization energies is achieved by using the strong oxidant tris(4-bromophenyl)ammoniumyl hexachloroantimonate (Magic Blue). In particular diketopyrrolopyrrole (DPP)-based copolymers reach a cond. of up to 100 S cm-1 and a thermoelec. power factor of 10μW m-1 K-2. Further, both ESR (EPR) as well as a combination of spectroelectrochem. and chronoamperometry is used to est. the charge-carrier d. of the polymer PDPP-3T doped with Magic Blue. A molar attenuation coeff. of 6.0 ± 0.2 × 103 m2 mol-1 is obtained for the first polaronic sub-bandgap absorption of electrochem. oxidized PDPP-3T. Comparison with chem. doped PDPP-3T suggests a charge-carrier d. on the order of 1026 m-3, which yields a charge-carrier mobility of up to 0.5 cm2 V-1 s-1 for the most heavily doped material.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtl2qsrvM&md5=e04dff86a15c6511fff34207b9aeff48
  34. 34
    Untilova, V.; Biskup, T.; Biniek, L.; Vijayakumar, V.; Brinkmann, M. Control of chain alignment and crystallization helps enhance charge conductivities and thermoelectric power factors in sequentially doped P3HT:F4TCNQ films. Macromolecules 2020, 53, 2441– 2453,  DOI: 10.1021/acs.macromol.9b02389
    Google Scholar
    34
    Control of Chain Alignment and Crystallization Helps Enhance Charge Conductivities and Thermoelectric Power Factors in Sequentially Doped P3HT:F4TCNQ Films
    Untilova, Viktoriia; Biskup, Till; Biniek, Laure; Vijayakumar, Vishnu; Brinkmann, Martin
    Macromolecules (Washington, DC, United States) (2020), 53 (7), 2441-2453CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Thermoelectricity has gained considerable interest in the past decade due to the advent of org. thermoelec. materials. Crystallinity and doping level crucially det. the thermoelec. figure of merit of semiconducting polymers. Hence, detailed insight into these factors is prerequisite for developing efficient devices. Here we show that the semicryst. structure of aligned P3HT films shows superior thermoelec. efficiencies as compared to the smectic-like phase because of both a higher in-plane orientation and a higher doping level. Conductivities up to 160 S/cm and power factors of 56μW m-1 K-2 along the rubbing direction are obtained vs. a few μW m-1 K-2 for nonoriented films. Different intercalation mechanisms of F4TCNQ in the layers of alkyl side chains are evidenced by electron diffraction in doped oriented films of the smectic-like and the semicryst. phases. We provide compelling evidence that doping of the smectic-like phase promotes ordering of P3HT backbones along the chain direction within individual π-stacks, whereas for the semicryst. phase dopant intercalation reorganizes the arrangement of successive π-stacks and perturbs the packing of alkyl side chains. Insight into the orientation of F4TCNQ- anions in the layers of alkyl side chains of P3HT crystals was further retrieved from a detailed polarized UV-vis-NIR spectroscopic anal. Our results demonstrate that both orientation of the polymer chains and crystallinity enhance the thermoelec. properties as well as the doping level. We anticipate that detailed control of polymer morphol. in films further improves the thermoelec. figure of merit of semiconducting polymers.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXltF2lsrs%253D&md5=3eeb8ac2ffd4e2386a14f7568f9d3908
  35. 35
    Veregin, R. P.; Harbour, J. R. Electron spin resonance spectroscopic study of electronic charge transport in an aromatic diamine. J. Phys. Chem. B 1990, 94, 6231– 6237,  DOI: 10.1021/j100379a016
    Google Scholar
    35
    Electron spin resonance spectroscopic study of electronic charge transport in an aromatic diamine
    Veregin, Richard P.; Harbour, John R.
    Journal of Physical Chemistry (1990), 94 (16), 6231-7CODEN: JPCHAX; ISSN:0022-3654.
    ESR spectra have been obtained for the radical cation of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) in dichloromethane soln., in solid amorphous films, and in TPD/polycarbonate films doped with tris(p-bromophenyl)ammoniumyl hexachloroantimonate or HNO3. By use of ESR the mediation of electronic charge (hole) transport via the TPD+ radical cation has been obsd. in the TPD films in the absence of an applied field. Arrhenius activation parameters were calcd. for charge transport from the ESR data, giving Ea = 10 ± 2 kJ/mol, A = (1.7 ± 1) × 1010 s-1, and a rate const. at 300 K of (3.1 ± 1) × 108 s-1. The value of Ea is one-half that from time-of-flight (TOF) measurements extrapolated to zero field, while the rate const. is a factor of 10 smaller, and A is a factor of 1000 smaller. The differences can be understood in terms of the compensation effect due to the presence of residual solvent, and the ion pairing of an TPD+ ions with dopant counterions. In TPD/polycarbonate films the rate of hole transport is too slow to produce significant changes in the ESR spectrum. The rate of charge transport is thus <2 × 108 -1 in these films, consistent with TOF data. In dichloromethane soln., and Ea of 9.8 kJ/mol was obsd. with ESR. Extrapolating the soln. data to solid TPD gives a hole transport rate of 9.74 × 109 s-1, a factor of 3 higher than that from TOF data. The lower Ea and higher rate in dichloromethane soln. are consistent with the effect of the higher dielec. const. compared to an TPD film. This suggests that the rate-detg. step for hole transport is the same in soln. as it is in the solid state.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3cXkvV2qu7o%253D&md5=ef3a15a7a4004892e2265757c4a0466a
  36. 36
    Kroon, R.; Kiefer, D.; Stegerer, D.; Yu, L.; Sommer, M.; Müller, C. Polar side chains enhance processability, electrical conductivity, and thermal stability of a molecularly p-doped polythiophene. Adv. Mater. 2017, 29, 1700930  DOI: 10.1002/adma.201700930
    Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Schröder, M.; Biskup, T. cwepr – A Python package for analysing cw-EPR data focussing on reproducibility and simple usage. J. Magn. Reson. 2022, 335, 107140  DOI: 10.1016/j.jmr.2021.107140
    Google Scholar
    37
    cwepr - A Python package for analysing cw-EPR data focussing on reproducibility and simple usage
    Schroder Mirjam; Biskup Till
    Journal of magnetic resonance (San Diego, Calif. : 1997) (2022), 335 (), 107140 ISSN:.
    Reproducibility is at the heart of science. Nevertheless, with the advent of computer-based data processing and analysis, most spectroscopists have a hard time fully reproducing a figure from last year's publication starting from the raw data. Unfortunately, this renders their work eventually unscientific. To change this, we need to develop analysis tools that relieve their users from having to trace each processing and analysis step. Furthermore, these tools need to be modular, extendible, and easy to use in order to get used. To this end, we present here the open-source Python package cwepr based on the ASpecD framework for reproducible analysis of spectroscopic data. This package follows best practices of both, science and software development. Key features include an automatically generated gap-less record of each individual processing and analysis step from the raw data to the final published figure. Additionally, it provides a powerful user interface requiring no programming skills of the user. Due to its code quality, modularity, and extensive documentation, it can be easily extended and is actively developed by spectroscopists working in the field. We expect this approach to have a high impact in the field and to help fighting the looming reproducibility crisis in spectroscopy.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB2M%252FltFOjtQ%253D%253D&md5=3500dae702d3c68673869adf8ef18dde
  38. 38
    Schröder, M.; Biskup, T. Cwepr Python Package, Zenodo 2021.
    Google Scholar
    There is no corresponding record for this reference.

Cited By

Click to copy section linkSection link copied!

This article is cited by 2 publications.

  1. Ross Warren, Eunkyung Cho, Hong Li, Jean-Luc Bredas, Norbert Koch. Understanding the Double Doping of Organic Semiconductors Via State Energy Renormalization upon Charging. ACS Materials Letters 2022, 4 (10) , 2051-2057. https://doi.org/10.1021/acsmaterialslett.2c00619
  2. Gustav Persson, Emmy Järsvall, Magnus Röding, Renee Kroon, Yadong Zhang, Stephen Barlow, Seth R. Marder, Christian Müller, Eva Olsson. Visualisation of individual dopants in a conjugated polymer: sub-nanometre 3D spatial distribution and correlation with electrical properties. Nanoscale 2022, 14 (41) , 15404-15413. https://doi.org/10.1039/D2NR03554E
Download PDF
Open PDF
Go to Chemistry of Materials
Get e-Alerts
Get e-Alerts

Chemistry of Materials

Cite this: Chem. Mater. 2022, 34, 12, 5673–5679
Click to copy citationCitation copied!
https://doi.org/10.1021/acs.chemmater.2c01040
Published June 13, 2022

Copyright © 2022 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Article Views

1754

Altmetric

-

Citations

2
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. Energy diagram showing the energy levels that are relevant for charge transfer from polymers p(g42T-T) and TQ1 to the p-type dopant Mo(tfd-COCF3)3.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. (a) UV–vis spectra of Mo(tfd-COCF3)3, [Mo(tfd-COCF3)3]−Et4N+, and [Mo(tfd-COCF3)3]2–(Et4N+)2 dissolved in dichloromethane (DCM). (b) EPR spectra of [Mo(tfd-COCF3)3]−Et4N+ and [Mo(tfd-COCF3)3]2–(Et4N+)2 dispersed in a matrix of poly(ethylene oxide) (PEO; see Figure S4 for nonsmoothed EPR spectra).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. (a) UV–vis–NIR absorbance spectra displaying the difference in thickness-normalized absorbance Δ(A/d) between the spectra of neat TQ1 and TQ1 doped with Magic Blue or Mo(tfd-COCF3)3. (b) EPR spectra of [Mo(tfd-COCF3)3]−Et4N+ dispersed in a PEO matrix and TQ1 doped with Mo(tfd-COCF3)3. The spectra have been normalized to the maximum in the field range 338–341.5 mT. (c) EPR spectra of TQ1 doped with Magic Blue or Mo(tfd-COCF3)3. The spectra have been normalized to the same amplitude.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. (a) UV–vis–NIR absorbance spectra displaying the difference in thickness-normalized absorbance Δ(A/d) between the spectra of neat p(g42T-T) and p(g42T-T) sequentially doped with Mo(tfd-COCF3)3 or [Mo(tfd-COCF3)3]−Et4N+. (b) EPR spectra of neat p(g42T-T) and p(g42T-T) sequentially doped with Mo(tfd-COCF3)3 or [Mo(tfd-COCF3)3]−Et4N+. (c) EPR spectra of co-processed p(g42T-T):Mo(tfd-COCF3)3 films (see Figures S9 and S11 for nonsmoothed EPR spectra).

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    This article references 38 other publications.

    1. 1
      Organic Flexible Electronics: Fundamentals, Devices, and Applications, 1st ed.; Cosseddu, P.; Caironi, M., Eds.; Woodhead Publishing: Duxford, UK, 2021.
      There is no corresponding record for this reference.
    2. 2
      Simon, D. T.; Gabrielsson, E. O.; Tybrandt, K.; Berggren, M. Organic Bioelectronics: Bridging the Signaling Gap between Biology and Technology. Chem. Rev. 2016, 116, 13009– 13041,  DOI: 10.1021/acs.chemrev.6b00146
      2
      Organic Bioelectronics: Bridging the Signaling Gap between Biology and Technology
      Simon, Daniel T.; Gabrielsson, Erik O.; Tybrandt, Klas; Berggren, Magnus
      Chemical Reviews (Washington, DC, United States) (2016), 116 (21), 13009-13041CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. The electronics in people's daily lives rely almost exclusively on electrons as the dominant charge carrier. In stark contrast, biol. systems rarely use electrons but rather use ions and mols. of varying size. Due to the unique combination of both electronic and ionic/mol. cond. in conducting and semiconducting org. polymers and small mols., these materials have emerged in recent decades as excellent tools for translating signals between these two realms and, therefore, providing a means to effectively interface biol. with conventional electronics, thus, the field of org. bioelectronics. Today, org. bioelectronics defines a generic platform with unprecedented biol. recording and regulation tools and is maturing toward applications ranging from life sciences to the clinic. In this Review, the authors introduce the field, from its early breakthroughs to its current results and future challenges.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtVyrur7I&md5=57086c8309a7d360d24fb813f44cb03f
    3. 3
      Lüssem, B.; Riede, M.; Leo, K. Doping of organic semiconductors. Phys. Status Solidi A 2013, 210, 9– 43,  DOI: 10.1002/pssa.201228310
      3
      Doping of organic semiconductors
      Luessem, B.; Riede, M.; Leo, K.
      Physica Status Solidi A: Applications and Materials Science (2013), 210 (1), 9-43CODEN: PSSABA; ISSN:1862-6300. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. The understanding and applications of org. semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small org. LED (OLED) displays; other areas of application such as OLED lighting and org. photovoltaics are on the verge of broad commercialization. Org. semiconductors are superior to inorg. ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, elec. doping of org. semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorg. semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evapd. org. layers with mol. dopants. Recently, both p- and n-type mol. dopants have been developed that lead to efficient and stable doping of org. thin films. Due to doping, the cond. of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between org. layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and org. solar cells is highlighted in this review. Overall, controlled mol. doping can be considered as key enabling technol. for many different org. device types that can lead to significant improvements in efficiencies and lifetimes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhvVyrtLbN&md5=3028d24bf630eae80c6ca787ab64e41b
    4. 4
      Jacobs, I. E.; Moulé, A. J. Controlling molecular doping in organic semiconductors. Adv. Mater. 2017, 29, 1703063  DOI: 10.1002/adma.201703063
      There is no corresponding record for this reference.
    5. 5
      Scaccabarozzi, A. D.; Basu, A.; Aniés, F.; Liu, J.; Zapata-Arteaga, O.; Warren, R.; Firdaus, Y.; Nugraha, M. I.; Lin, Y.; Campoy-Quiles, M.; Koch, N.; Müller, C.; Tsetseris, L.; Heeney, M.; Anthopoulos, T. D. Doping Approaches for Organic Semiconductors. Chem. Rev. 2022, 122, 4420– 4492,  DOI: 10.1021/acs.chemrev.1c00581
      5
      Doping Approaches for Organic Semiconductors
      Scaccabarozzi, Alberto D.; Basu, Aniruddha; Anies, Filip; Liu, Jian; Zapata-Arteaga, Osnat; Warren, Ross; Firdaus, Yuliar; Nugraha, Mohamad Insan; Lin, Yuanbao; Campoy-Quiles, Mariano; Koch, Norbert; Muller, Christian; Tsetseris, Leonidas; Heeney, Martin; Anthopoulos, Thomas D.
      Chemical Reviews (Washington, DC, United States) (2022), 122 (4), 4420-4492CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. Electronic doping in org. materials has remained an elusive concept for several decades. It drew considerable attention in the early days in the quest for org. materials with high elec. cond., paving the way for the pioneering work on pristine org. semiconductors (OSCs) and their eventual use in a plethora of applications. Despite this early trend, however, recent strides in the field of org. electronics have been made hand in hand with the development and use of dopants to the point that are now ubiquitous. Here, we give an overview of all important advances in the area of doping of org. semiconductors and their applications. We first review the relevant literature with particular focus on the phys. processes involved, discussing established mechanisms but also newly proposed theories. We then continue with a comprehensive summary of the most widely studied dopants to date, placing particular emphasis on the chem. strategies toward the synthesis of mols. with improved functionality. The processing routes toward doped org. films and the important doping-processing-nanostructure relationships, are also discussed. We conclude the review by highlighting how doping can enhance the operating characteristics of various org. devices.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXisFSgtLjJ&md5=1785c05b2620a3f751b0559c1865797a
    6. 6
      Li, J.; Duchemin, I.; Roscioni, O. M.; Friederich, P.; Anderson, M.; Da Como, E.; Kociok-Köhn, G.; Wenzel, W.; Zannoni, C.; Beljonne, D.; Blase, X.; D’Avino, G. Host dependence of the electron affinity of molecular dopants. Mater. Horiz. 2019, 6, 107– 114,  DOI: 10.1039/C8MH00921J
      6
      Host dependence of the electron affinity of molecular dopants
      Li, Jing; Duchemin, Ivan; Roscioni, Otello Maria; Friederich, Pascal; Anderson, Marie; Da Como, Enrico; Kociok-Kohn, Gabriele; Wenzel, Wolfgang; Zannoni, Claudio; Beljonne, David; Blase, Xavier; D'Avino, Gabriele
      Materials Horizons (2019), 6 (1), 107-114CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
      Charge carriers energetics is key in electron transfer processes such as those that enable the elec. doping of org. semiconductors. In this study, we take advantage of the quant. accuracy of embedded GW calcns. to perform a series of virtual expts. that allow measuring the electron affinity of p-type dopants in different host solids. Our calcns. show that the energy levels of a mol. impurity strongly depend on the host environment as a result of electrostatic intermol. interactions. In particular, the electron affinity of a dopant impurity in a given semiconductor is found to be up to 1 eV lower than that of the pure dopant crystal. This result questions the pertinence of the electron affinity measured for pure dopants in order to predict doping efficiency in a specific host. The role of the Coulomb electron-hole interaction for the dopant-to-semiconductor charge transfer and for the release of doping-induced charges is discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVejurzO&md5=93fc9d3dcb28a274fdda67ff8ce4a8ce
    7. 7
      Salzmann, I.; Heimel, G.; Oehzelt, M.; Winkler, S.; Koch, N. Molecular electrical doping of organic semiconductors: fundamental mechanisms and emerging dopant design rules. Acc. Chem. Res. 2016, 49, 370– 378,  DOI: 10.1021/acs.accounts.5b00438
      7
      Molecular Electrical Doping of Organic Semiconductors: Fundamental Mechanisms and Emerging Dopant Design Rules
      Salzmann, Ingo; Heimel, Georg; Oehzelt, Martin; Winkler, Stefanie; Koch, Norbert
      Accounts of Chemical Research (2016), 49 (3), 370-378CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
      A review. Today's information society depends on the authors' ability to controllably dope inorg. semiconductors, such as silicon, thereby tuning their elec. properties to application-specific demands. For optoelectronic devices, org. semiconductors, i.e., conjugated polymers and mols., have emerged as s superior alternative owing to the ease of tuning their optical gap through chem. variability and their potential for low-cost, large-area processing on flexible substrates. There, the potential of mol. elec. doping for improving the performance of, for example, org. light-emitting devices or org. solar cells has only recently been established. The doping efficiency, however, remains conspicuously low, highlighting the fact that the underlying mechanisms of mol. doping in org. semiconductors are only little understood compared with their inorg. counterparts. .Here, the authors review the broad range of phenomena obsd. upon molecularly doping org. semiconductors and identify two distinctly different scenarios: the pairwise formation of both org. semiconductor and dopant ions on one hand and the emergence of ground state charge transfer complexes between org. semiconductor and dopant through supramol. hybridization of their resp. frontier MOs on the other hand. Evidence for the occurrence of these two scenarios is subsequently discussed from the characteristic and strikingly different signatures of the individual species involved in the resp. doping processes in a variety of spectroscopic techniques. The crit. importance of a statistical view of doping, rather than a bimol. picture, is then highlighted by employing numerical simulations, which reveal one of the main differences between inorg. and org. semiconductors to be their resp. d. of electronic states and the doping induced changes thereof. Engineering the d. of states of doped org. semiconductors, the Fermi-Dirac occupation of which ultimately dets. the doping efficiency, thus emerges as key challenge. As a 1st step, the formation of charge transfer complexes is identified as being detrimental to the doping efficiency, which suggests sterically shielding the functional core of dopant mols. as an addnl. design rule to complement the requirement of low ionization energies or high electron affinities in efficient n-type or p-type dopants, resp. In an extended outlook, the authors finally argue that, to fully meet this challenge, an improved understanding is required of just how the admixt. of dopant mols. to org. semiconductors does affect the d. of states: compared with their inorg. counterparts, traps for charge carriers are omnipresent in org. semiconductors due to structural and chem. imperfections, and Coulomb attraction between ionized dopants and free charge carriers is typically stronger in org. semiconductors owing to their lower dielec. const. Nevertheless, encouraging progress is being made toward developing a unifying picture that captures the entire range of doping induced phenomena, from ion-pair to complex formation, in both conjugated polymers and mols. Once completed, such a picture will provide viable guidelines for synthetic and supramol. chem. that will enable further technol. advances in org. and hybrid org./inorg. devices.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFSjsrY%253D&md5=cc3b2014b0e798e89fa0f673aa011c7d
    8. 8
      Nell, B.; Ortstein, K.; Boltalina, O. V.; Vandewal, K. Influence of dopant–host energy level offset on thermoelectric properties of doped organic semiconductors. J. Phys. Chem. C 2018, 122, 11730– 11735,  DOI: 10.1021/acs.jpcc.8b03804
      8
      Influence of dopant-host energy level offset on thermoelectric properties of doped organic semiconductors
      Nell, Bernhard; Ortstein, Katrin; Boltalina, Olga V.; Vandewal, Koen
      Journal of Physical Chemistry C (2018), 122 (22), 11730-11735CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Increasing the amt. of charge carriers by mol. doping is important to improve the function of several org. electronic devices. In this work, the authors use highly fluorinated fullerene (C60F48) to p-type dope common amorphous mol. host materials. They observe a general relation between the material's elec. cond. and Seebeck coeff., both strongly depending on the energy level offset between the amorphous host and the dopant. This suggests that the doping efficiency at similar doping levels is mainly detd. by the electron transfer yield from host to dopant. Indeed, the dopant anion and host cation absorption strength correlate with the ionization energy (IE) of the host material. Host materials with an IE significantly below the electron affinity of the dopant yield the highest doping efficiency. Surprisingly, the doping efficiency reduces only by about 1 order of magnitude when the IE of the host material is increased by 0.55 eV, which they attribute to the disordered nature of the host materials.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptlyju7o%253D&md5=a665fe8b25ef7c15a9d82d8840e3752b
    9. 9
      Euvrard, J.; Revaux, A.; Bayle, P.-A.; Bardet, M.; Vuillaume, D.; Kahn, A. The formation of polymer-dopant aggregates as a possible origin of limited doping efficiency at high dopant concentration. Org. Electron. 2018, 53, 135– 140,  DOI: 10.1016/j.orgel.2017.11.020
      9
      The formation of polymer-dopant aggregates as a possible origin of limited doping efficiency at high dopant concentration
      Euvrard, Julie; Revaux, Amelie; Bayle, Pierre-Alain; Bardet, Michel; Vuillaume, Dominique; Kahn, Antoine
      Organic Electronics (2018), 53 (), 135-140CODEN: OERLAU; ISSN:1566-1199. (Elsevier B.V.)
      The polymer Poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b)dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno [3,4-b]thiophene-)-2-6-diyl] (PBDTTT-c) p-doped with the mol. dopant tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-COCF3)3) exhibits a decline in transport properties at high doping concns., which limits the performance attainable through org. semiconductor doping. SEM is used to correlate the evolution of hole cond. and hopping transport activation energy with the formation of aggregates in the layer. Transmission Electron Microscopy with energy-dispersive X-ray anal. along with liq.-state NMR expts. are carried out to det. the compn. of the aggregates. This study offers an explanation to the limited efficiency of doping at high dopant concns. and reinforces the need to increase doping efficiency in order to be able to reduce the dopant concn. and not neg. affect cond.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvV2qsLnF&md5=2ed763a7e6ecd26eff1f7ea43d3188b1
    10. 10
      Duong, D. T.; Wang, C.; Antono, E.; Toney, M. F.; Salleo, A. The chemical and structural origin of efficient p-type doping in P3HT. Org. Electron. 2013, 14, 1330– 1336,  DOI: 10.1016/j.orgel.2013.02.028
      10
      The chemical and structural origin of efficient p-type doping in P3HT
      Duong, Duc T.; Wang, Chenchen; Antono, Erin; Toney, Michael F.; Salleo, Alberto
      Organic Electronics (2013), 14 (5), 1330-1336CODEN: OERLAU; ISSN:1566-1199. (Elsevier B.V.)
      We investigate the chem. and structural properties of soln.-processed thin films of P3HT blended with p-type dopant F4TCNQ. The max. in-plane elec. cond. of doped films is obsd. at a molar doping fraction of 0.17, in agreement with the binding mechanism of F4TCNQ:P3HT complexes. Through the use of X-ray diffraction, a previously unreported cryst. phase is obsd. for P3HT films doped above a crit. threshold concn. This cryst. phase involves the incorporation of F4TCNQ mols. into ordered polymer regions and ultimately improves charge dissocn., leading to higher carrier d. in thin film. Finally, optical absorption and X-ray diffraction reveal that the chem. state of P3HT in soln. has a dramatic impact on the elec. and structural properties of the blended films.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXmt1Clsr8%253D&md5=dbe1ccee73b6e2e48528dfd1b29d2623
    11. 11
      Dixon, A. L.; Vezin, H.; Nguyen, T.-Q.; Reddy, G. N. M. Structural insights into Lewis acid- and F4TCNQ-doped conjugated polymers by solid-state magnetic resonance spectroscopy. Mater. Horiz. 2022, 9, 981– 990,  DOI: 10.1039/D1MH01574E
      11
      Structural insights into Lewis acid- and F4TCNQ-doped conjugated polymers by solid-state magnetic resonance spectroscopy
      Dixon, Alana L.; Vezin, Herve; Nguyen, Thuc-Quyen; Reddy, G. N. Manjunatha
      Materials Horizons (2022), 9 (3), 981-990CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
      Mol. doping strategies facilitate orders of magnitude enhancement in the charge carrier mobility of org. semiconductors (OSCs). Understanding the different doping mechanisms and mol.-level constraints on doping efficiency related to the material energy levels is crucial to develop versatile dopants for OSCs. Given the compositional and structural heterogeneities assocd. with OSC thin films, insight into dopant-polymer interactions by long-range techniques such as X-ray scattering and electron microscopy is exceedingly challenging to obtain. This study employs short-range probes, solid-state (ss) NMR and EPR spectroscopy, to resolve local structures and intermol. interactions between dopants such as F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), Lewis acid BCF (tris[pentafluorophenyl] borane) and Lewis base conjugated polymer, PCPDTBT (P4) (poly[2,6-(4,4-bis(2-hexadecyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]). Anal. of 1H and 13C ssNMR spectra of P4, P4 : F4TCNQ and P4 : BCF blends indicates that the addn. of dopants induces local structural changes in the P4 polymer, and causes paramagnetism-induced signal broadening and intensity losses. The hyperfine interactions in P4 : BCF and P4 : F4TCNQ are characterized by two-dimensional pulsed EPR spectroscopy. For P4 : F4TCNQ, 19F ssNMR anal. indicates that the F4TCNQ mols. are distributed and aggregated into different local chem. environments.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xislyruw%253D%253D&md5=2b5536c04d37fbe501f3fe322f9fbca7
    12. 12
      Kiefer, D.; Kroon, R.; Hofmann, A. I.; Sun, H.; Liu, X.; Giovannitti, A.; Stegerer, D.; Cano, A.; Hynynen, J.; Yu, L.; Zhang, Y.; Nai, D.; Harrelson, T. F.; Sommer, M.; Moulé, A. J.; Kemerink, M.; Marder, S. R.; McCulloch, I.; Fahlman, M.; Fabiano, S.; Müller, C. Double doping of conjugated polymers with monomer molecular dopants. Nat. Mater. 2019, 18, 149– 155,  DOI: 10.1038/s41563-018-0263-6
      12
      Double doping of conjugated polymers with monomer molecular dopants
      Kiefer, David; Kroon, Renee; Hofmann, Anna I.; Sun, Hengda; Liu, Xianjie; Giovannitti, Alexander; Stegerer, Dominik; Cano, Alexander; Hynynen, Jonna; Yu, Liyang; Zhang, Yadong; Nai, Dingqi; Harrelson, Thomas F.; Sommer, Michael; Moule, Adam J.; Kemerink, Martijn; Marder, Seth R.; McCulloch, Iain; Fahlman, Mats; Fabiano, Simone; Muller, Christian
      Nature Materials (2019), 18 (2), 149-155CODEN: NMAACR; ISSN:1476-1122. (Nature Research)
      Mol. doping is a crucial tool for controlling the charge-carrier concn. in org. semiconductors. Each dopant mol. is commonly thought to give rise to only one polaron, leading to a max. of one donor:acceptor charge-transfer complex and hence an ionization efficiency of 100%. However, this theor. limit is rarely achieved because of incomplete charge transfer and the presence of unreacted dopant. Here, we establish that common p-dopants can in fact accept two electrons per mol. from conjugated polymers with a low ionization energy. Each dopant mol. participates in two charge-transfer events, leading to the formation of dopant dianions and an ionization efficiency of up to 200%. Furthermore, we show that the resulting integer charge-transfer complex can dissoc. with an efficiency of up to 170%. The concept of double doping introduced here may allow the dopant fraction required to optimize charge conduction to be halved.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmt1Oktbs%253D&md5=f3b09a943b9edecf64ef493a17f35ba3
    13. 13
      Goel, M.; Siegert, M.; Krauss, G.; Mohanraj, J.; Hochgesang, A.; Heinrich, D. C.; Fried, M.; Pflaum, J.; Thelakkat, M. HOMO–HOMO electron transfer: An elegant strategy for p-type doping of polymer semiconductors toward thermoelectric applications. Adv. Mater. 2020, 32, 2003596  DOI: 10.1002/adma.202003596
      13
      HOMO-HOMO Electron Transfer: An Elegant Strategy for p-Type Doping of Polymer Semiconductors toward Thermoelectric Applications
      Goel, Mahima; Siegert, Marie; Krauss, Gert; Mohanraj, John; Hochgesang, Adrian; Heinrich, David C.; Fried, Martina; Pflaum, Jens; Thelakkat, Mukundan
      Advanced Materials (Weinheim, Germany) (2020), 32 (43), 2003596CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Unlike the conventional p-doping of org. semiconductors (OSCs) using acceptors, here, an efficient doping concept for diketopyrrolopyrrole-based polymer PDPP[T]2-EDOT (OSC-1) is presented using an oxidized p-type semiconductor, Spiro-OMeTAD(TFSI)2 (OSC-2), exploiting electron transfer from HOMOOSC-1 to HOMOOSC-2. A shift of work function toward the HOMOOSC-1 upon doping is confirmed by UPS. Detailed XPS and UV-vis-NIR absorption studies confirm HOMOOSC-1 to HOMOOSC-2 electron transfer. The redn. products of Spiro-OMeTAD(TFSI)2 to Spiro-OMeTAD(TFSI)2 and Spiro-OMeTAD is also confirmed and their relative amts. in doped samples is detd. Mott-Schottky anal. shows two orders of magnitude increase in free charge carrier d. and one order of magnitude increase in the charge carrier mobility. The cond. increases considerably by four orders of magnitude to a max. of 10 S m-1 for a very low doping ratio of 8 mol%. The doped polymer films exhibit high thermal and ambient stability resulting in a max. power factor of 0.07μW m-1 K-2 at a Seebeck coeff. of 140μV K-1 for a very low doping ratio of 4 mol%. Also, the concept of HOMOOSC-1 to HOMOOSC-2 electron transfer is a highly efficient, stable and generic way to p-dope other conjugated polymers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhvVKgtrnI&md5=876167efc0f58974212d37ef0110fa16
    14. 14
      Krauss, G.; Hochgesang, A.; Mohanraj, J.; Thelakkat, M. Highly Efficient Doping of Conjugated Polymers Using Multielectron Acceptor Salts. Macromol. Rapid Commun. 2021, 42, 2100443  DOI: 10.1002/marc.202100443
      14
      Highly Efficient Doping of Conjugated Polymers Using Multielectron Acceptor Salts
      Krauss, Gert; Hochgesang, Adrian; Mohanraj, John; Thelakkat, Mukundan
      Macromolecular Rapid Communications (2021), 42 (22), 2100443CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Chem. doping is a vital tool for tuning electronic properties of conjugated polymers. Most single electron acceptors used for p-doping necessitate high dopant concns. to achieve good elec. cond. However, high-molar doping ratios hamper doping efficiency. Here a new concept of using multielectron acceptor (MEA) salts as dopants for conjugated polymers is presented. Two novel MEA salts are synthesized and their doping efficiency to toward two polymers differing in their dielec. properties are compared with two single electron acceptors such as NOPF6 and magic blue. Cutting-edge methods such as UPS/XPS, impedance spectroscopy, and d. of states anal. in addn. to UV-vis-NIR absorption, spectroelectrochem., and Raman spectroscopy methods are used to characterize the doped systems. The tetracation salt improves the cond. by two orders of magnitude and quadruples the charge carrier concn. compared to single electron acceptors for the same molar ratio. The differences in charge carrier d. and activation energy on doping are delineated. Further, a strong dependency of the carrier release on the polymer polarity is obsd. High carrier densities at reduced dopant loadings and improved doping efficacies using MEA dopants offer a highly efficient doping strategy for conjugated polymers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitlWntL7N&md5=5705cbc1e4040e4d8056c51a0860a43c
    15. 15
      Paniagua, S. A.; Baltazar, J.; Sojoudi, H.; Mohapatra, S. K.; Zhang, S.; Henderson, C. L.; Graham, S.; Barlow, S.; Marder, S. R. Production of heavily n- and p-doped CVD graphene with solution-processed redox-active metal–organic species. Mater. Horiz. 2014, 1, 111– 115,  DOI: 10.1039/C3MH00035D
      15
      Production of heavily n- and p-doped CVD graphene with solution-processed redox-active metal-organic species
      Paniagua, Sergio A.; Baltazar, Jose; Sojoudi, Hossein; Mohapatra, Swagat K.; Zhang, Siyuan; Henderson, Clifford L.; Graham, Samuel; Barlow, Stephen; Marder, Seth R.
      Materials Horizons (2014), 1 (1), 111-115CODEN: MHAOBM; ISSN:2051-6355. (Royal Society of Chemistry)
      CVD graphene has been n- and p-doped using redox-active, soln.-processed metal-org. complexes. Elec. measurements, photoemission spectroscopies, and Raman spectroscopy were used to characterize the doped films and give insights into the changes. The work function decreased by as much as 1.3 eV with the n-dopant, with contributions from electron transfer and surface dipole, and the cond. significantly increased.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVShsbrO&md5=04a92aad248993ed5ec2c436060abd60
    16. 16
      Mohapatra, S. K.; Zhang, Y.; Sandhu, B.; Fonari, M. S.; Timofeeva, T. V.; Marder, S. R.; Barlow, S. Synthesis, characterization, and crystal structures of molybdenum complexes of unsymmetrical electron-poor dithiolene ligands. Polyhedron 2016, 116, 88– 95,  DOI: 10.1016/j.poly.2016.04.025
      16
      Synthesis, characterization, and crystal structures of molybdenum complexes of unsymmetrical electron-poor dithiolene ligands
      Mohapatra, Swagat K.; Zhang, Yadong; Sandhu, Bhupinder; Fonari, Marina S.; Timofeeva, Tatiana V.; Marder, Seth R.; Barlow, Stephen
      Polyhedron (2016), 116 (), 88-95CODEN: PLYHDE; ISSN:0277-5387. (Elsevier Ltd.)
      Mo(S2C2(CF3)2)3, 1a, has proven a useful p-dopant in org. electronics. To develop more sol. p-dopants, MoS2-9 was treated with alkynes CF3CCCO2Me and CF3CCCOCF3 to give the dianions of the corresponding tris(dithiolene) complexes, 1b2- and 1c2-, resp., which were then oxidized to neutral molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene], 1b, and molybdenum tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene], 1c, using NO+PF-6. The crystal structures of (NEt+4)21b2-, (NEt+4)21c2-, and neutral 1c have been detd. In all three cases, the metal coordination is approx. trigonal prismatic and the major isomer is cis (approx. C3v). The structure of 1b2- is distorted by a twist towards pseudo-octahedral coordination similar to that seen in structures of 1a2- and Mo(S2C2(CO2Me)2)2-3, 1d2-, salts, and that of 1c exhibits marked folds between the planes formed by the ligand atoms and those formed by the Mo and coordinated S atoms, similar to those seen in the structure of 1a. On the other hand, the metal dithiolene core of 1c2- is essentially undistorted from C3v symmetry. The oxidant strength of the neutral mols. increases in the order 1d < 1b < 1a < 1c, with the potentials ranging from -0.02 to +0.39 V vs. the ferrocenium/ferrocene couple.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XmvFyjtLw%253D&md5=9d72fafaa35554b0ab8ea2fe669913e1
    17. 17
      Qi, Y.; Sajoto, T.; Barlow, S.; Kim, E.-G.; Brédas, J.-L.; Marder, S. R.; Kahn, A. Use of a High Electron-Affinity Molybdenum Dithiolene Complex to p-Dope Hole-Transport Layers. J. Am. Chem. Soc. 2009, 131, 12530– 12531,  DOI: 10.1021/ja904939g
      17
      Use of a High Electron-Affinity Molybdenum Dithiolene Complex to p-Dope Hole-Transport Layers
      Qi, Yabing; Sajoto, Tissa; Barlow, Stephen; Kim, Eung-Gun; Bredas, Jean-Luc; Marder, Seth R.; Kahn, Antoine
      Journal of the American Chemical Society (2009), 131 (35), 12530-12531CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Exptl. and theor. results are presented on the electronic structure of molybdenum tris[1,2-bis(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd)3), a high electron-affinity organometallic complex that constitutes a promising candidate as a p-dopant for org. mol. semiconductors. The electron affinity of the compd., detd. via inverse photoemission spectroscopy, is 5.6 eV, which is 0.4 eV larger than that of the commonly used p-dopant F4-TCNQ. The LUMO level of Mo(tfd)3 is calcd. to be delocalized over the whole mol., which is expected to lead to low pinning potential. Efficient p-doping of a std. hole transport material (α-NPD) is demonstrated via measurements of Fermi level shifts and enhanced cond. in α-NPD:1% Mo(tfd)3. Rutherford backscattering measurements show good stability of the three-dimensional Mo(tfd)3 mol. in the host matrix with respect to diffusion.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXpvV2nt70%253D&md5=5fac0de719f3555a67f9afc195facaca
    18. 18
      Hynynen, J.; Järsvall, E.; Kroon, R.; Zhang, Y.; Barlow, S.; Marder, S. R.; Kemerink, M.; Lund, A.; Müller, C. Enhanced thermoelectric power factor of tensile drawn poly(3-hexylthiophene). ACS Macro Lett. 2019, 8, 70– 76,  DOI: 10.1021/acsmacrolett.8b00820
      18
      Enhanced Thermoelectric Power Factor of Tensile Drawn Poly(3-hexylthiophene)
      Hynynen, Jonna; Jaersvall, Emmy; Kroon, Renee; Zhang, Yadong; Barlow, Stephen; Marder, Seth R.; Kemerink, Martijn; Lund, Anja; Muller, Christian
      ACS Macro Letters (2019), 8 (1), 70-76CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      The thermoelec. power factor of a broad range of org. semiconductors scales with their elec. cond. according to a widely obeyed power law, and therefore, strategies that permit this empirical trend to be surpassed are highly sought after. Here, tensile drawing of the conjugated polymer, poly(3-hexylthiophene), (P3HT), is employed to create free-standing films with a high degree of uniaxial alignment. Along the direction of orientation, sequential doping with a molybdenum tris(dithiolene) complex leads to a 5-fold enhancement of the power factor beyond the predicted value, reaching up to 16 μW m-1 K-2 for a cond. of about 13 S cm-1. Neither stretching nor doping affect the glass transition temp. of P3HT, giving rise to robust free-standing materials that are of interest for the design of flexible thermoelec. devices.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisFyrsr7K&md5=33ea2ed7251d1cd45b6f41be95a700fa
    19. 19
      Untilova, V.; Hynynen, J.; Hofmann, A. I.; Scheunemann, D.; Zhang, Y.; Barlow, S.; Kemerink, M.; Marder, S. R.; Biniek, L.; Müller, C.; Brinkmann, M. High thermoelectric power factor of poly(3-hexylthiophene) through in-plane alignment and doping with a molybdenum dithiolene complex. Macromolecules 2020, 53, 6314– 6321,  DOI: 10.1021/acs.macromol.0c01223
      19
      High Thermoelectric Power Factor of Poly(3-hexylthiophene) through In-Plane Alignment and Doping with a Molybdenum Dithiolene Complex
      Untilova, Viktoriia; Hynynen, Jonna; Hofmann, Anna I.; Scheunemann, Dorothea; Zhang, Yadong; Barlow, Stephen; Kemerink, Martijn; Marder, Seth R.; Biniek, Laure; Muller, Christian; Brinkmann, Martin
      Macromolecules (Washington, DC, United States) (2020), 53 (15), 6314-6321CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Here we report a record thermoelec. power factor of up to 160μW m-1 K-2 for the conjugated polymer poly(3-hexylthiophene) (P3HT). This result is achieved through the combination of high-temp. rubbing of thin films together with the use of a large molybdenum dithiolene p-dopant with a high electron affinity. Comparison of the UV-vis-NIR spectra of the chem. doped samples to electrochem. oxidized material reveals an oxidn. level of 10%, i.e. one polaron for every 10 repeat units. The high power factor arises due to an increase in the charge-carrier mobility and hence elec. cond. along the rubbing direction. We conclude that P3HT, with its facile synthesis and outstanding processability, should not be ruled out as a potential thermoelec. material.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhsVajtLfM&md5=82504474af50f8b0649799ecd43821f9
    20. 20
      Yamashita, Y.; Tsurumi, J.; Kurosawa, T.; Ueji, K.; Tsuneda, Y.; Kohno, S.; Kempe, H.; Kumagai, S.; Okamoto, T.; Takeya, J.; Watanabe, S. Supramolecular cocrystals built through redox-triggered ion intercalation in π-conjugated polymers. Commun. Mater. 2021, 2, 45  DOI: 10.1038/s43246-021-00148-9
      20
      Supramolecular cocrystals built through redox-triggered ion intercalation in π-conjugated polymers
      Yamashita, Yu; Tsurumi, Junto; Kurosawa, Tadanori; Ueji, Kan; Tsuneda, Yukina; Kohno, Shinya; Kempe, Hideto; Kumagai, Shohei; Okamoto, Toshihiro; Takeya, Jun; Watanabe, Shun
      Communications Materials (2021), 2 (1), 45CODEN: CMOAGE; ISSN:2662-4443. (Nature Portfolio)
      Self-organization in π-conjugated polymers gives rise to a highly ordered lamellar structure, in which inter-chain stacking spontaneously forms two-dimensional conjugated sheets. This multi-layer stacked nature of semicryst. polymers allows the inclusion of various functional mols. In particular, redox-triggered ion-intercalation is an ideal system for mol. doping, for which extremely high charge carrier d. has been achieved. Here, we conducted a detailed structural anal. and electron d. simulation to pinpoint exactly where the guest dopants are located periodically in the void space in a polymer's lamellae. Our findings are indicative of an intercalation compd. of layered polymers and a guest intercalant. We show that a homogeneous cocrystal structure can be realized throughout the host polymer medium, which is proved by the observation of coherent carrier transport. The intercalation cocrystal nature gives the best achievable doping level in semicryst. polymers and excellent environmental stability. These findings should open up possibilities for tuning the collective dynamics of functional mols. through intercalation phenomena.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XotVCkt78%253D&md5=45655daf5fa42837638a5b8f23d4865e
    21. 21
      Jacobs, I. E.; Lin, Y.; Huang, Y.; Ren, X.; Simatos, D.; Chen, C.; Tjhe, D.; Statz, M.; Lai, L.; Finn, P. A.; Neal, W. G.; D’Avino, G.; Lemaur, V.; Fratini, S.; Beljonne, D.; Strzalka, J.; Nielsen, C. B.; Barlow, S.; Marder, S. R.; McCulloch, I.; Sirringhaus, H. High-efficiency ion-exchange doping of conducting polymers. Adv. Mater. 2021, 2102988  DOI: 10.1002/adma.202102988
      There is no corresponding record for this reference.
    22. 22
      Euvrard, J.; Revaux, A.; Nobre, S. S.; Kahn, A.; Vuillaume, D. Toward a better understanding of the doping mechanism involved in Mo(tfd-COCF3)3 doped PBDTTT-c. J. Appl. Phys. 2018, 123, 225501  DOI: 10.1063/1.5029810
      22
      Toward a better understanding of the doping mechanism involved in Mo(tfd-COCF3)3 doped PBDTTT-c
      Euvrard, J.; Revaux, A.; Nobre, S. S.; Kahn, A.; Vuillaume, D.
      Journal of Applied Physics (Melville, NY, United States) (2018), 123 (22), 225501/1-225501/10CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
      The authors aim to improve the understanding of the doping mechanism involved in the polymer poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b')dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno [3,4-b]thiophene-)-2-6-diyl)]] (PBDTTT-c) doped with tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] [Mo(tfd-COCF3)3]. The authors follow the evolution of the hole d. with dopant concn. to highlight the limits of org. semiconductor doping. To enable the use of doping to enhance the performance of org. electronic devices, doping efficiency must be understood and improved. The authors report here a study using complementary optical and elec. characterization techniques, which sheds some light on the origin of this limited doping efficiency at a high dopant concn. Two doping mechanisms are considered, the direct charge transfer and the charge transfer complex. The validity of the model involved as well as its impact on the doping efficiency are discussed. (c) 2018 American Institute of Physics.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFemtbrK&md5=dd28ddbea73d60f054d11d1b97a7e22c
    23. 23
      Nunes Domschke, T.; Bardagot, O.; Benayad, A.; Demadrille, R.; Carella, A.; Clerc, R.; Pereira, A. Unraveling the mechanism behind air instability in thin semiconducting polymer layers p-doped with molybdenum dithiolene complexes. Synth. Met. 2020, 260, 116251  DOI: 10.1016/j.synthmet.2019.116251
      23
      Unraveling the mechanism behind air instability in thin semiconducting polymer layers p-doped with molybdenum dithiolene complexes
      Nunes Domschke, Tamara; Bardagot, Olivier; Benayad, Anass; Demadrille, Renaud; Carella, Alexandre; Clerc, Raphael; Pereira, Alexandre
      Synthetic Metals (2020), 260 (), 116251CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier B.V.)
      Doping efficiency and stability are crucial requirements for the integration of doped org. semiconductors in optoelectronic devices. This work presents a detailed exptl. study on the air stability of p-doped systems based on a low-bandgap polymer, poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b')dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2-6-diyl] (PBDTTT-c) doped with a strong mol. p-dopant, i.e. molybdenum tris[1-(trifluoroethanoyl)-2-(trifluoromethyl) ethane-1,2-dithiolene] (Mo(tfd-COCF3)3). The elec. cond. and the optical absorption are measured for different dopant concns. in argon atm., and their variations monitored as a function of the air exposure time. The results indicate a clear instability under ambient air related to a dedoping process, which is particularly pronounced in ultra-thin (< 50 nm) doped layers. By evaluating the stability of the p-doped polymer layers under different atmospheres (ambient air, anhyd. air and argon), the detrimental impact of moisture and/or O2(H20)n complexes is highlighted. XPS revealed that the p-doping instability in ambient air can be assigned to changes in the oxidn. state of the metallic center as well as to an intrinsic degrdn. of the dopant mol. This study unravels an important degrdn. mechanism with this class of dopants that should be taken under consideration and solved for future integration of ultrathin p-doped layers in printed electronic devices.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXisVSrsL7P&md5=2d2ba5075414c0ec3197862e9d63c632
    24. 24
      Barrière, F.; Camire, N.; Geiger, W. E.; Mueller-Westerhoff, U. T.; Sanders, R. Use of Medium Effects to Tune the ΔE1/2 Values of Bimetallic and Oligometallic Compounds. J. Am. Chem. Soc. 2002, 124, 7262– 7263,  DOI: 10.1021/ja020309d
      24
      Use of Medium Effects to Tune the ΔE1/2 Values of Bimetallic and Oligometallic Compounds
      Barriere, Frederic; Camire, Nicole; Geiger, William E.; Mueller-Westerhoff, Ulrich T.; Sanders, Richard
      Journal of the American Chemical Society (2002), 124 (25), 7262-7263CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The redox potentials of bis(fulvalene)dinickel (1), and the tetrakis(ferrocenyl)nickel dithiolene complex (2) were measured in a variety of nonaq. electrolytes. The difference in E1/2 values of the two successive 1-electron oxidns. of 1 (i.e., ΔE1/2 values) increased from a low of 212 mV in anisole/[NBu4]Cl to a high of 850 mV in CH2Cl2-Na[B(C6H3(CF3)2)4], reflecting an increase of over 1010 in the comproportionation const. (Kcomp = [1+]2/[1][12+]). Six reversible 1-electron processes are possible for compd. 2, the four oxidns. arising from the ferrocenyl substituents, and the two redns. arising from the Ni dithiolene moiety. The E1/2 spreads of the four oxidn. waves and the two redn. waves are both highly sensitive to medium effects. For both 1 and 2, the largest ΔE1/2 values for cationic products are found in solvents of low polarity and donor strength contg. electrolyte salts having large anions and small cations. Conversely, the smallest ΔE1/2 values for anionic products are found under these conditions, culminating in the observation of a single two-electron redn. wave for 2/22- in CH2Cl2-Na[B(C6H3(CF3)2)4]. A combination of solvation and ion-pairing effects must be considered, and may be used to advantage, when using ΔE1/2 values as a measure of electronic interactions between redox centers in compds. contg. two or more electron-transfer sites.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XktVKjtrk%253D&md5=7dccf3082653716809854d440bb204c1
    25. 25
      Zokaei, S.; Kroon, R.; Gladisch, J.; Paulsen, B. D.; Sohn, W.; Hofmann, A. I.; Persson, G.; Stamm, A.; Syrén, P.-O.; Olsson, E.; Rivnay, J.; Stavrinidou, E.; Lund, A.; Müller, C. Toughening of a Soft Polar Polythiophene through Copolymerization with Hard Urethane Segments. Adv. Sci. 2021, 8, 2002778  DOI: 10.1002/advs.202002778
      25
      Toughening of a Soft Polar Polythiophene through Copolymerization with Hard Urethane Segments
      Zokaei, Sepideh; Kroon, Renee; Gladisch, Johannes; Paulsen, Bryan D.; Sohn, Wonil; Hofmann, Anna I.; Persson, Gustav; Stamm, Arne; Syren, Per-Olof; Olsson, Eva; Rivnay, Jonathan; Stavrinidou, Eleni; Lund, Anja; Mueller, Christian
      Advanced Science (Weinheim, Germany) (2021), 8 (2), 2002778CODEN: ASDCCF; ISSN:2198-3844. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temp. and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported. The mol. design is contrary to that of other semiconductor-insulator copolymers, which typically combine a soft nonconjugated spacer with hard conjugated segments. Copolymn. of polar polythiophenes and urethane segments results in a ductile material that can be used as a free-standing solid. The copolymer displays a storage modulus of 25 MPa at room temp., elongation at break of 95%, and a reduced degree of swelling due to hydrogen bonding. Both chem. doping and electrochem. oxidn. reveal that the introduction of urethane segments does not unduly reduce the hole charge-carrier mobility and ability to take up charge. Further, stable operation is obsd. when the copolymer is used as the active layer of org. electrochem. transistors.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXps1yls7s%253D&md5=0b476b3c0f3193fc4793e8372f53b14e
    26. 26
      Wang, E.; Hou, L.; Wang, Z.; Hellström, S.; Zhang, F.; Inganäs, O.; Andersson, M. R. An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells. Adv. Mater. 2010, 22, 5240– 5244,  DOI: 10.1002/adma.201002225
      26
      An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells
      Wang, Ergang; Hou, Lintao; Wang, Zhongqiang; Hellstroem, Stefan; Zhang, Fengling; Inganaes, Olle; Andersson, Mats R.
      Advanced Materials (Weinheim, Germany) (2010), 22 (46), 5240-5244CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The authors report an easily synthesized donor-acceptor (D-A) type of low bandgap polymer based on thiophene and quinoxaline named poly[2,3-bis(3-octyloxyphenyl)quinoxaline-5,8-diyl-thiophene-2,5-diyl] (TQ1) and explore its application in polymer solar cells. This polymer structure and its optical properties have previously been disclosed by Yamamoto et al.(l9). Recently, several similar polymers with different side chains were synthesized with low mol. wts., showing poor photovoltaic performance. In this paper, the authors modify the synthesis of the monomers and also TQ1 and investigate its optical, electrochem. and photovoltaic properties. After early optimization of the prepn. of the solar cells, a max. power point (MPP) up to 6 mW/m2 was achieved with a high VOC of ca. 0.9 V from a blend of TQ1 and [70]PCBM under illumination from an air mass 1.5 global (AM 1.5G) solar simulator (100 mW/cm2).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsFClurfP&md5=f2eb255e12121eb15db2986eb7665859
    27. 27
      Kroon, R.; Gehlhaar, R.; Steckler, T. T.; Henriksson, P.; Müller, C.; Bergqvist, J.; Hadipour, A.; Heremans, P.; Andersson, M. R. New quinoxaline and pyridopyrazine-based polymers for solution-processable photovoltaics. Sol. Energy Mater. Sol. Cells 2012, 105, 280– 286,  DOI: 10.1016/j.solmat.2012.06.029
      27
      New quinoxaline and pyridopyrazine-based polymers for solution-processable photovoltaics
      Kroon, Renee; Gehlhaar, Robert; Steckler, Timothy T.; Henriksson, Patrik; Mueller, Christian; Bergqvist, Jonas; Hadipour, Afshin; Heremans, Paul; Andersson, Mats R.
      Solar Energy Materials & Solar Cells (2012), 105 (), 280-286CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)
      The recently published quinoxaline/thiophene-based polymer TQ1 has been modified on its acceptor unit, either altering the acceptor strength by incorporating a pyridopyrazine, substitution of the acceptor-hydrogens by fluorine, or substitution of the alkoxy side chain by alkyl. The changes in phys., electronic and device properties are discussed. For the polymers incorporating the stronger acceptors a decreased performance is found, where in both cases the current in the devices is compromised. Incorporation of the pyridopyrazine-based acceptor seems to result in more severe or addnl. loss mechanisms compared to the polymer that incorporates the fluorine atoms. A similar performing material is obtained when changing the alkoxy side chain in TQ1 to an alkyl, where the solar cell performance is mainly improved on the fill factor. It is demonstrated that the std. TQ1 structure is easily modified in a no. of ways, showing the versatility and robustness of the std. TQ1 structure and synthesis.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFWht7vO&md5=fb41d26ced86b73565aead4e53aaa201
    28. 28
      Arvind, M.; Tait, C. E.; Guerrini, M.; Krumland, J.; Valencia, A. M.; Cocchi, C.; Mansour, A. E.; Koch, N.; Barlow, S.; Marder, S. R.; Behrends, J.; Neher, D. Quantitative Analysis of Doping-Induced Polarons and Charge-Transfer Complexes of Poly(3-hexylthiophene) in Solution. J. Phys. Chem. B 2020, 124, 7694– 7708,  DOI: 10.1021/acs.jpcb.0c03517
      28
      Quantitative Analysis of Doping-Induced Polarons and Charge-Transfer Complexes of Poly(3-hexylthiophene) in Solution
      Arvind, Malavika; Tait, Claudia E.; Guerrini, Michele; Krumland, Jannis; Valencia, Ana M.; Cocchi, Caterina; Mansour, Ahmed E.; Koch, Norbert; Barlow, Stephen; Marder, Seth R.; Behrends, Jan; Neher, Dieter
      Journal of Physical Chemistry B (2020), 124 (35), 7694-7708CODEN: JPCBFK; ISSN:1520-5207. (American Chemical Society)
      The mechanism and the nature of the species formed by mol. doping of the model polymer poly(3-hexylthiophene) (P3HT) in its regioregular (rre-) and regiorandom (rra-) forms in soln. are investigated for three different dopants: the prototypical π-electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), the strong Lewis acid tris(pentafluorophenyl)borane (BCF), and the strongly oxidizing complex molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-CO2Me)3). In a combined optical and ESR study, we show that the doping of rreP3HT in soln. occurs by integer charge transfer, resulting in formation of P3HT radical cations (polarons) for all of the dopants considered here. Remarkably, despite the different chem. nature of the dopants and dopant-polymer interaction, the formed polarons exhibit essentially identical optical absorption spectra. The situation is very different for the doping of rraP3HT, where we observe formation of a charge-transfer complex with F4TCNQ and of a "localized" P3HT polaron on nonaggregated chains upon doping with BCF, while there is no indication of dopant-induced species in the case of Mo(tfd-CO2Me)3. We est. the ionization efficiency of the resp. dopants for the two polymers in soln. and report the molar extinction coeff. spectra of the three different species. Finally, we observe increased spin delocalization in regioregular compared to regiorandom P3HT by electron nuclear double resonance, suggesting that the ability of the charge to delocalize on aggregates of planarized polymer backbones plays a significant role in detg. the doping mechanism.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXht1alsLnO&md5=b1d21484bf514780f2a2d9c63a6b952f
    29. 29
      Fekl, U.; Sarkar, B.; Kaim, W.; Zimmer-De Iuliis, M.; Nguyen, N. Tuning of the Spin Distribution between Ligand- and Metal-Based Spin: Electron Paramagnetic Resonance of Mixed-Ligand Molybdenum Tris(dithiolene) Complex Anions. Inorg. Chem. 2011, 50, 8685– 8687,  DOI: 10.1021/ic201047k
      29
      Tuning of the Spin Distribution between Ligand- and Metal-Based Spin: Electron Paramagnetic Resonance of Mixed-Ligand Molybdenum Tris(dithiolene) Complex Anions
      Fekl, Ulrich; Sarkar, Biprajit; Kaim, Wolfgang; Zimmer-De Iuliis, Marco; Nguyen, Neilson
      Inorganic Chemistry (2011), 50 (18), 8685-8687CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      ESR spectra of homoleptic and mixed-ligand molybdenum tris(dithiolene) complex anions [Mo(tfd)m(bdt)n]- (n + m = 3; bdt = S2C6H4; tfd = S2C2(CF3)2) showed that the spin d. had mixed metal-ligand character with more ligand-based spin for [Mo(tfd)3]- and a higher degree of metal-based spin for [Mo(bdt)3]-. The magnitude of the isotropic 95,97Mo hyperfine interaction increased continuously, by a factor of 2.5, on going from the former to the latter. The mixed complexes were in between, and the metal character of the spin increased with the bdt content. The expts. were corroborated by d. functional theory computations, which reproduced this steady increase in metal-based character.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGnu7rO&md5=137ddc2c26aedb716a36d7d5cd5d4dcd
    30. 30
      Davison, A.; Edelstein, N.; Holm, R. H.; Maki, A. H. Synthetic and Electron Spin Resonance Studies of Six-Coordinate Complexes Related by Electron-Transfer Reactions. J. Am. Chem. Soc. 1964, 86, 2799– 2805,  DOI: 10.1021/ja01068a010
      30
      Synthetic and electron spin resonance (E.S.R.) studies of six-coordinate complexes related by electron-transfer reactions
      Davison, A.; Edelstein, N.; Holm, R. H.; Maki, A. H.
      Journal of the American Chemical Society (1964), 86 (14), 2799-805CODEN: JACSAT; ISSN:0002-7863.
      A new series of 6-coordinate complexes of the general type [MS6-C6R6]2 with R = CF3 (M = Cr, Mo, W, z = 0, 1-, 2-) and R = CN(M = Cr, V, z = 2-; M = Cr; z = 3-)was prepd. These complexes are similar to related bis complexes in that they contain metals stabilized in several different oxidn. states, and complexes of given R and M can be interconverted by simple oxidn.-redn. reactions. The syntheses of all compds. are described in detail, and chem. stabilities are discussed in terms of polarog. half-wave potentials. The results of magnetic susceptibility, E.S.R., and IR studies are discussed. E.S.R. results show the presence of a strong trigonal component in the octahedral ligand field in complexes with a doublet ground state, and are not in agreement with the conventional d01 or (a1*)1 ground state. Probable electronic structures of these complexes are discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF2cXkt12msrs%253D&md5=55df56f9f6234ad1b2696b4e8a0390aa
    31. 31
      Tenderholt, A. L.; Szilagyi, R. K.; Holm, R. H.; Hodgson, K. O.; Hedman, B.; Solomon, E. I. Electronic Control of the “Bailar Twist” in Formally d0-d2 Molybdenum Tris(dithiolene) Complexes: A Sulfur K-edge X-ray Absorption Spectroscopy and Density Functional Theory Study. Inorg. Chem. 2008, 47, 6382– 6392,  DOI: 10.1021/ic800494h
      31
      Electronic Control of the "Bailar Twist" in Formally d-d2 Molybdenum Tris(dithiolene) Complexes: A Sulfur K-edge X-ray Absorption Spectroscopy and Density Functional Theory Study
      Tenderholt, Adam L.; Szilagyi, Robert K.; Holm, Richard H.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.
      Inorganic Chemistry (2008), 47 (14), 6382-6392CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      Sulfur K-edge X-ray absorption spectroscopy (XAS) and d. functional theory (DFT-GGA) calcns. have been used to det. the electronic structures of a series of Mo tris(dithiolene) complexes, [Mo(mdt)3]z (where mdt = 1,2-dimethylethene-1,2-dithiolate(2-) and z = 2-, 1-, 0), with near trigonal-prismatic geometries (D3h symmetry). These results show that the formally MoIV, MoV, and MoVI complexes actually have a (dz2)2 configuration, i.e., remain effectively MoIV despite oxidn. Comparisons with the XAS data of another set of Mo tris(dithiolene) complexes, [Mo(tbbdt)3]z (where tbbdt = 3,5-di-tert-butylbenzene-1,2-dithiolate(2-) and z = 1-, 0), show that both neutral complexes, [Mo(mdt)3] and [Mo(tbbdt)3], have similar electronic structures while the monoanions do not. Calcns. reveal that the "Bailar twist" present in the crystal structure of [Mo(tbbdt)3]1- (D3 symmetry) but not [Mo(mdt)3]1- (D3h symmetry) is controlled by electronic factors which arise from bonding differences between the mdt and tbbdt ligands. In the former, CI between the Mo dz2 and a deeper energy, occupied ligand orbital, which occurs in D3 symmetry, destabilizes the Mo dz2 to above another ligand orbital which is half-occupied in the D3h [Mo(mdt)3]1- complex. This leads to a metal d1 configuration with no ligand holes (i.e., d1[L3]0h) for [Mo(tbbdt)3]1- rather than the metal d2 configuration with one ligand hole (i.e., d2[L3]1h) for [Mo(mdt)3]1-. Thus, the Bailar twist obsd. in some metal tris(dithiolene) complexes is the result of CI between metal and ligand orbitals and can be probed exptl. by S K-edge XAS.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXms1agtrg%253D&md5=fb2b3c2e3d4d4a81799dde053635c05a
    32. 32
      Connelly, N. G.; Geiger, W. E. Chemical Redox Agents for Organometallic Chemistry. Chem. Rev. 1996, 96, 877– 910,  DOI: 10.1021/cr940053x
      32
      Chemical Redox Agents for Organometallic Chemistry
      Connelly, Neil G.; Geiger, William E.
      Chemical Reviews (Washington, D. C.) (1996), 96 (2), 877-910CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review, with >461 refs., showing how one-electron oxidants and reductants have been used in preparative chem. (incorporating both synthetic applications and generation of species for in situ characterization) in nonaq. solns., the usual media for organometallic ET reactions. The authors do not treat photochem.-generated reducing agents which, although generally transient species, may have advantages in some applications.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XhsVGhu7Y%253D&md5=205b204d99818aded3c41067d4bf85e3
    33. 33
      Hofmann, A. I.; Kroon, R.; Zokaei, S.; Järsvall, E.; Malacrida, C.; Ludwigs, S.; Biskup, T.; Müller, C. Chemical doping of conjugated polymers with the strong oxidant magic blue. Adv. Electron. Mater. 2020, 6, 2000249  DOI: 10.1002/aelm.202000249
      33
      Chemical Doping of Conjugated Polymers with the Strong Oxidant Magic Blue
      Hofmann, Anna I.; Kroon, Renee; Zokaei, Sepideh; Jaersvall, Emmy; Malacrida, Claudia; Ludwigs, Sabine; Biskup, Till; Mueller, Christian
      Advanced Electronic Materials (2020), 6 (8), 2000249CODEN: AEMDBW; ISSN:2199-160X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Mol. doping of org. semiconductors is a powerful tool for the optimization of org. electronic devices and org. thermoelec. materials. However, there are few redox dopants that have a sufficiently high electron affinity to allow the doping of conjugated polymers with an ionization energy of more than 5.3 eV. Here, p-doping of a broad palette of conjugated polymers with high ionization energies is achieved by using the strong oxidant tris(4-bromophenyl)ammoniumyl hexachloroantimonate (Magic Blue). In particular diketopyrrolopyrrole (DPP)-based copolymers reach a cond. of up to 100 S cm-1 and a thermoelec. power factor of 10μW m-1 K-2. Further, both ESR (EPR) as well as a combination of spectroelectrochem. and chronoamperometry is used to est. the charge-carrier d. of the polymer PDPP-3T doped with Magic Blue. A molar attenuation coeff. of 6.0 ± 0.2 × 103 m2 mol-1 is obtained for the first polaronic sub-bandgap absorption of electrochem. oxidized PDPP-3T. Comparison with chem. doped PDPP-3T suggests a charge-carrier d. on the order of 1026 m-3, which yields a charge-carrier mobility of up to 0.5 cm2 V-1 s-1 for the most heavily doped material.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtl2qsrvM&md5=e04dff86a15c6511fff34207b9aeff48
    34. 34
      Untilova, V.; Biskup, T.; Biniek, L.; Vijayakumar, V.; Brinkmann, M. Control of chain alignment and crystallization helps enhance charge conductivities and thermoelectric power factors in sequentially doped P3HT:F4TCNQ films. Macromolecules 2020, 53, 2441– 2453,  DOI: 10.1021/acs.macromol.9b02389
      34
      Control of Chain Alignment and Crystallization Helps Enhance Charge Conductivities and Thermoelectric Power Factors in Sequentially Doped P3HT:F4TCNQ Films
      Untilova, Viktoriia; Biskup, Till; Biniek, Laure; Vijayakumar, Vishnu; Brinkmann, Martin
      Macromolecules (Washington, DC, United States) (2020), 53 (7), 2441-2453CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Thermoelectricity has gained considerable interest in the past decade due to the advent of org. thermoelec. materials. Crystallinity and doping level crucially det. the thermoelec. figure of merit of semiconducting polymers. Hence, detailed insight into these factors is prerequisite for developing efficient devices. Here we show that the semicryst. structure of aligned P3HT films shows superior thermoelec. efficiencies as compared to the smectic-like phase because of both a higher in-plane orientation and a higher doping level. Conductivities up to 160 S/cm and power factors of 56μW m-1 K-2 along the rubbing direction are obtained vs. a few μW m-1 K-2 for nonoriented films. Different intercalation mechanisms of F4TCNQ in the layers of alkyl side chains are evidenced by electron diffraction in doped oriented films of the smectic-like and the semicryst. phases. We provide compelling evidence that doping of the smectic-like phase promotes ordering of P3HT backbones along the chain direction within individual π-stacks, whereas for the semicryst. phase dopant intercalation reorganizes the arrangement of successive π-stacks and perturbs the packing of alkyl side chains. Insight into the orientation of F4TCNQ- anions in the layers of alkyl side chains of P3HT crystals was further retrieved from a detailed polarized UV-vis-NIR spectroscopic anal. Our results demonstrate that both orientation of the polymer chains and crystallinity enhance the thermoelec. properties as well as the doping level. We anticipate that detailed control of polymer morphol. in films further improves the thermoelec. figure of merit of semiconducting polymers.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXltF2lsrs%253D&md5=3eeb8ac2ffd4e2386a14f7568f9d3908
    35. 35
      Veregin, R. P.; Harbour, J. R. Electron spin resonance spectroscopic study of electronic charge transport in an aromatic diamine. J. Phys. Chem. B 1990, 94, 6231– 6237,  DOI: 10.1021/j100379a016
      35
      Electron spin resonance spectroscopic study of electronic charge transport in an aromatic diamine
      Veregin, Richard P.; Harbour, John R.
      Journal of Physical Chemistry (1990), 94 (16), 6231-7CODEN: JPCHAX; ISSN:0022-3654.
      ESR spectra have been obtained for the radical cation of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) in dichloromethane soln., in solid amorphous films, and in TPD/polycarbonate films doped with tris(p-bromophenyl)ammoniumyl hexachloroantimonate or HNO3. By use of ESR the mediation of electronic charge (hole) transport via the TPD+ radical cation has been obsd. in the TPD films in the absence of an applied field. Arrhenius activation parameters were calcd. for charge transport from the ESR data, giving Ea = 10 ± 2 kJ/mol, A = (1.7 ± 1) × 1010 s-1, and a rate const. at 300 K of (3.1 ± 1) × 108 s-1. The value of Ea is one-half that from time-of-flight (TOF) measurements extrapolated to zero field, while the rate const. is a factor of 10 smaller, and A is a factor of 1000 smaller. The differences can be understood in terms of the compensation effect due to the presence of residual solvent, and the ion pairing of an TPD+ ions with dopant counterions. In TPD/polycarbonate films the rate of hole transport is too slow to produce significant changes in the ESR spectrum. The rate of charge transport is thus <2 × 108 -1 in these films, consistent with TOF data. In dichloromethane soln., and Ea of 9.8 kJ/mol was obsd. with ESR. Extrapolating the soln. data to solid TPD gives a hole transport rate of 9.74 × 109 s-1, a factor of 3 higher than that from TOF data. The lower Ea and higher rate in dichloromethane soln. are consistent with the effect of the higher dielec. const. compared to an TPD film. This suggests that the rate-detg. step for hole transport is the same in soln. as it is in the solid state.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3cXkvV2qu7o%253D&md5=ef3a15a7a4004892e2265757c4a0466a
    36. 36
      Kroon, R.; Kiefer, D.; Stegerer, D.; Yu, L.; Sommer, M.; Müller, C. Polar side chains enhance processability, electrical conductivity, and thermal stability of a molecularly p-doped polythiophene. Adv. Mater. 2017, 29, 1700930  DOI: 10.1002/adma.201700930
      There is no corresponding record for this reference.
    37. 37
      Schröder, M.; Biskup, T. cwepr – A Python package for analysing cw-EPR data focussing on reproducibility and simple usage. J. Magn. Reson. 2022, 335, 107140  DOI: 10.1016/j.jmr.2021.107140
      37
      cwepr - A Python package for analysing cw-EPR data focussing on reproducibility and simple usage
      Schroder Mirjam; Biskup Till
      Journal of magnetic resonance (San Diego, Calif. : 1997) (2022), 335 (), 107140 ISSN:.
      Reproducibility is at the heart of science. Nevertheless, with the advent of computer-based data processing and analysis, most spectroscopists have a hard time fully reproducing a figure from last year's publication starting from the raw data. Unfortunately, this renders their work eventually unscientific. To change this, we need to develop analysis tools that relieve their users from having to trace each processing and analysis step. Furthermore, these tools need to be modular, extendible, and easy to use in order to get used. To this end, we present here the open-source Python package cwepr based on the ASpecD framework for reproducible analysis of spectroscopic data. This package follows best practices of both, science and software development. Key features include an automatically generated gap-less record of each individual processing and analysis step from the raw data to the final published figure. Additionally, it provides a powerful user interface requiring no programming skills of the user. Due to its code quality, modularity, and extensive documentation, it can be easily extended and is actively developed by spectroscopists working in the field. We expect this approach to have a high impact in the field and to help fighting the looming reproducibility crisis in spectroscopy.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BB2M%252FltFOjtQ%253D%253D&md5=3500dae702d3c68673869adf8ef18dde
    38. 38
      Schröder, M.; Biskup, T. Cwepr Python Package, Zenodo 2021.
      There is no corresponding record for this reference.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.chemmater.2c01040.

    • UV–vis–NIR spectra as well as angular-dependent and nonsmoothed EPR spectra (PDF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.