Ultrafast Time-Domain Spectroscopy Reveals Coherent Vibronic Couplings upon Electronic Excitation in Crystalline Organic Thin FilmsClick to copy article linkArticle link copied!
- Somayeh SouriSomayeh SouriInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Somayeh Souri
- Daniel TimmerDaniel TimmerInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Daniel Timmer
- Daniel C. LünemannDaniel C. LünemannInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Daniel C. Lünemann
- Naby HadilouNaby HadilouInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Naby Hadilou
- Katrin WinteKatrin WinteInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Katrin Winte
- Antonietta De SioAntonietta De SioInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyCenter for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Antonietta De Sio
- Martin EsmannMartin EsmannInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyCenter for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Martin Esmann
- Franziska CurdtFranziska CurdtInstitut für Biologie, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Franziska Curdt
- Michael WinklhoferMichael WinklhoferInstitut für Biologie, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Michael Winklhofer
- Sebastian AnhäuserSebastian AnhäuserFachbereich Physik, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, GermanyMore by Sebastian Anhäuser
- Michele GuerriniMichele GuerriniInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Michele Guerrini
- Ana M. ValenciaAna M. ValenciaInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Ana M. Valencia
- Caterina CocchiCaterina CocchiInstitut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyCenter for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Caterina Cocchi
- Gregor WitteGregor WitteFachbereich Physik, Philipps-Universität Marburg, Renthof 7, 35032 Marburg, GermanyMore by Gregor Witte
- Christoph Lienau*Christoph Lienau*[email protected]Institut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyCenter for Nanoscale Dynamics (CENAD), Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyResearch Centre for Neurosensory Sciences, Carl von Ossietzky Universität, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, GermanyMore by Christoph Lienau
Abstract
The coherent coupling between electronic excitations and vibrational modes of molecules largely affects the optical and charge transport properties of organic semiconductors and molecular solids. To analyze these couplings by means of ultrafast spectroscopy, highly ordered crystalline films with large domains are particularly suitable because the domains can be addressed individually, hence allowing azimuthal polarization-resolved measurements. Impressive examples of this are highly ordered crystalline thin films of perfluoropentacene (PFP) molecules, which adopt different molecular orientations on different alkali halide substrates. Here, we report polarization-resolved time-domain vibrational spectroscopy with 10 fs time resolution and Raman spectroscopy of crystalline PFP thin films grown on NaF(100) and KCl(100) substrates. Coherent oscillations in the time-resolved spectra reveal vibronic coupling to a high-frequency, 25 fs, in-plane deformation mode that is insensitive to the optical polarization, while the coupling to a lower-frequency, 85 fs, out-of-plane ring bending mode depends significantly on the crystalline and molecular orientation. Comparison with calculated Raman spectra of isolated PFP molecules in vacuo supports this interpretation and indicates a dominant role of solid-state effects in the vibronic properties of these materials. Our results represent a first step toward uncovering the role of anisotropic vibronic couplings for singlet fission processes in crystalline molecular thin films.
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Mode | Experimental |FT| spectrum | Experimental Raman spectrum | Experimental ref (32) | Simulated Raman spectrum | ||||
---|---|---|---|---|---|---|---|---|
Mode number (30) | Symmetry (30) | Frequency (cm–1) | Amplitude (norm.) | Frequency (cm–1) | Amplitude (norm.) | Frequency (cm–1) | Frequency (cm–1) | Amplitude (norm.) |
#16 | Ag | 178 | 0.32 | 179 | 0.15 | 178 | 173 | 0.09 |
#22 | Ag | 284 | 0.11 | 284 | 0.10 | 280 | 275 | 0.04 |
#36 | B2g | 384 | 0.85 | 392 | 1.00 | 389 | 396 | 0.01 |
#42 | Ag | 451 | 0.08 | 453 | 0.09 | 450 | 442 | 0.00 |
#45 | Ag | 490 | 0.14 | 494 | 0.01 | 492 | 482 | 0.10 |
#58 | Ag | 673 | 0.03 | 670 | 691 | 0.03 | ||
#62 | B3g | 774 | 0.23 | 775 | 0.16 | 770 | 771 | 0.01 |
#75 | Ag | 1210 | 0.03 | 1207 | 1198 | 0.00 | ||
#80 | Ag | 1238 | 0.00 | 1236 | 1233 | 0.53 | ||
#84 | Ag | 1320 | 1.00 | 1315 | 0.27 | 1317 | 1355 | 1.00 |
#86 | Ag | 1336 | 0.38 | 1337 | 1384 | 0.57 | ||
#99 | Ag | 1587 | 0.06 | 1583 | 0.08 | 1591 | 1573 | 0.10 |
The experimentally measured mode frequencies are compared to values from ref (32) and from the DFT calculations performed in this work.
Methods
Sample Preparation and Sample Growth
Coherent Vibrational Spectroscopy
Raman Spectroscopy
Analysis of Pump–Probe Data
Calculation of IR and Raman Spectra
Data Availability
All data supporting the findings are presented in the Letter and Supporting Information in graphic form. Experimental raw data and simulation results will be provided by the authors upon reasonable request.
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.jpclett.4c02711.
X-ray diffraction of PFP films on KCl and NaF; polarization-resolved UV/vis absorption spectra of single crystalline PFP islands on KCl and NaF; pulse characterization; fluence study; data analysis (PDF)
Transparent Peer Review report available (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.
Acknowledgments
The authors would like to acknowledge financial support from Deutsche Forschungsgemeinschaft (SFB 1372 magnetoreception and navigation in vertebrates, project number 395940726, INST 184/163-1, INST 184/164-1, Li 580/16-1, DE 3578/3-1, 223848855-SFB 1083 TP A2 and INST 184/222-1 (Confocal Raman Microscope)). We also acknowledge financial support from the Niedersächsische Ministerium für Wissenschaft und Kultur (DyNano and Wissenschaftsraum ElLiKo within the programme “zukunft.niedersachsen”), the Volkswagen Foundation (SMART). Computational resources were provided by the CARL Cluster at the Carl-von-Ossietzky University, Oldenburg, supported by the DFG and the Niedersächsisches MWK. C. C. acknowledges additional funding from the Federal Ministry of Education and Research (Professorinnenprogramm III) and from the Niedersächsische Ministerium für Wissenschaft und Kultur (Professorinnen für Niedersachsen). We thank L. Gütay for help with the Raman measurements.
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- 18Singh, S.; Jones, W. J.; Siebrand, W.; Stoicheff, B. P.; Schneider, W. G. Laser Generation of Excitons and Fluorescencence in Anthracene Crystals. J. Chem. Phys. 1965, 42 (1), 330– 342, DOI: 10.1063/1.1695695Google ScholarThere is no corresponding record for this reference.
- 19Smith, M. B.; Michl, J. Singlet Fission. Chem. Rev. 2010, 110 (11), 6891– 6936, DOI: 10.1021/cr1002613Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlKntbbF&md5=4632198f6c4b979ef92822fd6a3be047Singlet FissionSmith, Millicent B.; Michl, JosefChemical Reviews (Washington, DC, United States) (2010), 110 (11), 6891-6936CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. A theory of singlet fission is discussed along with its relation to photovoltaics. The literature is reviewed dealing with singlet fission in org. chromophores from the time of initial discovery of singlet fission to the present day.
- 20Smith, M. B.; Michl, J. Recent Advances in Singlet Fission. Annu. Rev. Phys. Chem. 2013, 64, 361– 386, DOI: 10.1146/annurev-physchem-040412-110130Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntVCrsrY%253D&md5=763960f83db3bb2586b496278a8f1506Recent advances in singlet fissionSmith, Millicent B.; Michl, JosefAnnual Review of Physical Chemistry (2013), 64 (), 361-386CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)A review. A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited mol. shares its energy with a ground-state neighbor to produce two triplet excited mols. It has been obsd. to occur in single-crystal, polycryst., and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivs., and it is argued that a wider structural variety would be desirable. The current state of the development of mol. structure design rules, based on first-principles theor. considerations, is described along with initial examples of implementation.
- 21Monahan, N.; Zhu, X. Y. Charge Transfer-Mediated Singlet Fission. Annu. Rev. Phys. Chem. 2015, 66, 601– 618, DOI: 10.1146/annurev-physchem-040214-121235Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXnvFart7Y%253D&md5=4d571e4127b62c7dfc19275861b0cdcbCharge transfer-mediated singlet fissionMonahan, N.; Zhu, X.-Y.Annual Review of Physical Chemistry (2015), 66 (), 601-618CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews)Singlet fission, the splitting of a singlet exciton into two triplet excitons in mol. materials, is interesting not only as a model many-electron problem, but also as a process with potential applications in solar energy conversion. Here we discuss limitations of the conventional four-electron and mol. dimer model in describing singlet fission in cryst. org. semiconductors, such as pentacene and tetracene. We emphasize the need to consider electronic delocalization, which is responsible for the decisive role played by the Mott-Wannier exciton, also called the charge transfer (CT) exciton, in mediating singlet fission. At the strong electronic coupling limit, the initial excitation creates a quantum superposition of singlet, CT, and triplet-pair states, and we present exptl. evidence for this interpretation. We also discuss the most recent attempts at translating this mechanistic understanding into design principles for CT state-mediated intramol. singlet fission in oligomers and polymers.
- 22Walker, B. J.; Musser, A. J.; Beljonne, D.; Friend, R. H. Singlet Exciton Fission in Solution. Nat. Chem. 2013, 5 (12), 1019– 1024, DOI: 10.1038/nchem.1801Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhslygtbnL&md5=99dc6ccf7cd3d1cfbe0ca35149633490Singlet exciton fission in solutionWalker, Brian J.; Musser, Andrew J.; Beljonne, David; Friend, Richard H.Nature Chemistry (2013), 5 (12), 1019-1024CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermol. coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solns. of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene mol. The intermediate breaks up when the two triplets sep. to each TIPS-pentacene mol. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight.
- 23Wilson, M. W.; Rao, A.; Ehrler, B.; Friend, R. H. Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics Toward Devices. Acc. Chem. Res. 2013, 46 (6), 1330– 1338, DOI: 10.1021/ar300345hGoogle Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntFWnsL8%253D&md5=c4b74ef2c17945aeb7c70edbb4630f28Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics toward DevicesWilson, Mark W. B.; Rao, Akshay; Ehrler, Bruno; Friend, Richard H.Accounts of Chemical Research (2013), 46 (6), 1330-1338CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. Singlet exciton fission is the process in conjugated org. mols. by which a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers 1st reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These studies used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest was recently re-kindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating addnl. photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chem., and small-mol. device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycryst. thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, the authors review the results of recent transient absorption and device-based studies of polycryst. pentacene. The authors address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, demonstration that triplet excitons generated via singlet fission in pentacene can be dissocd. at an interface with a suitable electron acceptor, such as fullerenes and IR-absorbing inorg. semiconducting quantum dots are discussed. The authors highlight recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous Si photovoltaic device. Although substantive challenges remain, both to better understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an IR-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could 1 day surpass the Shockley-Queisser limit.
- 24Musser, A. J.; Liebel, M.; Schnedermann, C.; Wende, T.; Kehoe, T. B.; Rao, A.; Kukura, P. Evidence for Conical Intersection Dynamics Mediating Ultrafast Singlet Exciton Fission. Nat. Phys. 2015, 11 (4), 352– 357, DOI: 10.1038/nphys3241Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXksVCmtbc%253D&md5=ba4f5c4e76401feaa359eb1dc2dee453Evidence for conical intersection dynamics mediating ultrafast singlet exciton fissionMusser, Andrew J.; Liebel, Matz; Schnedermann, Christoph; Wende, Torsten; Kehoe, Tom B.; Rao, Akshay; Kukura, PhilippNature Physics (2015), 11 (4), 352-357CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)Singlet exciton fission is the process in org. semiconductors through which a spin-singlet exciton converts into a pair of spin-triplet excitons residing on different chromophores, entangled in an overall spin-zero state. For some systems, singlet fission has been shown to occur on the 100 fs timescale and with a 200% quantum yield, but the mechanism of this process remains uncertain. Here we study a model singlet fission system, TIPS-pentacene, using ultrafast vibronic spectroscopy. We observe that vibrational coherence in the initially photogenerated singlet state is transferred to the triplet state and show that this behavior is effectively identical to ultrafast internal conversion for polyenes in soln. This similarity in vibronic dynamics suggests that both multi-mol. singlet fission and single-mol. internal conversion are mediated by the same underlying relaxation processes, based on strong coupling between nuclear and electronic degrees of freedom. In its most efficient form this leads to a conical intersection between the coupled electronic states.
- 25Chan, W.-L.; Ligges, M.; Jailaubekov, A.; Kaake, L.; Miaja-Avila, L.; Zhu, X.-Y. Observing the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron Transfer. Science 2011, 334 (6062), 1541– 1545, DOI: 10.1126/science.1213986Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs1aju7vP&md5=641eb0459d5cc473874c67e162d41a6bObserving the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron TransferChan, Wai-Lun; Ligges, Manuel; Jailaubekov, Askat; Kaake, Loren; Miaja-Avila, Luis; Zhu, X.-Y.Science (Washington, DC, United States) (2011), 334 (6062), 1541-1545CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Two for One Conventional solar cells create a charge carrier each time a photon of light at or above a certain energy threshold is absorbed. Any energy embedded in short-wavelength photons that exceeds the threshold is largely wasted. Semonin et al. (p. ) now demonstrate a nanoparticulate lead selenide solar cell that channels a fraction of the excess energy into current. Chan et al. (p. ) explored the fundamental dynamics of multiple carrier generation in an org. (rather than inorg.) absorber and characterized a short-lived state that bridges the high-energy single carrier state and two discrete lower-energy carrier states. Multiple exciton generation (MEG) refers to the creation of two or more electron-hole pairs from the absorption of one photon. Although MEG holds great promise, it proved challenging to implement, and questions remain about the underlying photo-phys. dynamics in nanocryst. as well as mol. media. Using the model system of pentacene/fullerene bilayers and femtosecond nonlinear spectroscopies, the authors directly obsd. the multiexciton (ME) state ensuing from singlet fission (a mol. manifestation of MEG) in pentacene. Probably the state exists in coherent superposition with the singlet populated by optical excitation. Also multiple electron transfer from the ME state to the fullerene occurs on a subpicosecond time scale, which is one order of magnitude faster than that from the triplet exciton state.
- 26Duan, H.-G.; Jha, A.; Li, X.; Tiwari, V.; Ye, H.; Nayak, P. K.; Zhu, X.-L.; Li, Z.; Martinez, T. J.; Thorwart, M. Intermolecular Vibrations Mediate Ultrafast Singlet Fission. Sci. Adv. 2020, 6 (38), eabb0052 DOI: 10.1126/sciadv.abb0052Google ScholarThere is no corresponding record for this reference.
- 27Seiler, H.; Krynski, M.; Zahn, D.; Hammer, S.; Windsor, Y. W.; Vasileiadis, T.; Pflaum, J.; Ernstorfer, R.; Rossi, M.; Schwoerer, H. Nuclear Dynamics of Singlet Exciton Fission in Pentacene Single Crystals. Sci. Adv. 2021, 7 (26), eabg0869 DOI: 10.1126/sciadv.abg0869Google ScholarThere is no corresponding record for this reference.
- 28Neef, A.; Beaulieu, S.; Hammer, S.; Dong, S.; Maklar, J.; Pincelli, T.; Xian, R. P.; Wolf, M.; Rettig, L.; Pflaum, J. Orbital-Resolved Observation of Singlet Fission. Nature 2023, 616 (7956), 275– 279, DOI: 10.1038/s41586-023-05814-1Google ScholarThere is no corresponding record for this reference.
- 29Kim, J.; Bain, D. C.; Ding, V.; Majumder, K.; Windemuller, D.; Feng, J.; Wu, J.; Patil, S.; Anthony, J.; Kim, W. Coherent photoexcitation of entangled triplet pair states. Nat. Chem. 2024, 16, 1680– 1686, DOI: 10.1038/s41557-024-01556-3Google ScholarThere is no corresponding record for this reference.
- 30Breuer, T.; Celik, M. A.; Jakob, P.; Tonner, R.; Witte, G. Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor Crystals. J. Phys. Chem. C 2012, 116 (27), 14491– 14503, DOI: 10.1021/jp304080gGoogle Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XosFemu70%253D&md5=8ae3f27e4fbc339da7737775099adde5Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor CrystalsBreuer, Tobias; Celik, Mehmet A.; Jakob, Peter; Tonner, Ralf; Witte, GregorJournal of Physical Chemistry C (2012), 116 (27), 14491-14503CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Vibrational properties of highly ordered cryst. perfluoropentacene (PFP) films epitaxially grown on KCl(100) and NaF(100) substrates were studied by transmission IR spectroscopy and d. functional theory. The different mol. orientations adopted by PFP on both substrates (standing vs. lying) and their epitaxial ordering enable precise polarization-resolved measurements along individual crystallog. directions and thus allow an unambiguous exptl. detn. of the polarization of the IR modes. Computations of the vibrational spectra beyond the single-mol. approxn. were employed at the periodic dispersion-cor. d. functional level (PBE-D2PBC) and compared with nonperiodic calcns. (PBE-D2/def2-TZVPP). Thereby, a detailed mode assignment based on vibrational energies and polarization information was attained. A microscopic explanation for the exptl. obsd. Davydov splitting of some modes and the IR inactivity of others was derived based on the mutual coupling of the dynamical dipole moments of the 2 mols. within the unit cell. Exptl. obsd. modes not covered by theor. anal. were identified as combination bands of IR-active modes coupled to totally sym. modes of similar displacement patterns. These findings have important implications for future studies on structure and charge transport in org. semiconductors and the validation of theor. approaches for the modeling of vibrational spectra.
- 31Kolata, K.; Breuer, T.; Witte, G.; Chatterjee, S. Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors. ACS Nano 2014, 8 (7), 7377– 7383, DOI: 10.1021/nn502544dGoogle Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVaht7jI&md5=db8009c7b8ceddc719b227075c07cd19Molecular Packing Determines Singlet Exciton Fission in Organic SemiconductorsKolata, Kolja; Breuer, Tobias; Witte, Gregor; Chatterjee, SangamACS Nano (2014), 8 (7), 7377-7383CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Carrier multiplication by singlet exciton fission enhances photovoltaic conversion efficiencies in org. solids. This decay of 1 singlet exciton into 2 triplet states allows the extn. of ≤2 electrons per harvested photon and promises to overcome the Shockley-Queisser limit. The microscopic mechanism of singlet exciton fission, esp. the relation between mol. packing and electronic response, remains unclear, which therefore hampers the systematic improvement of org. photovoltaic devices. For the model system perfluoropentacene, exptl. singlet exciton fission is greatly enhanced for a slip-stacked mol. arrangement by addressing different crystal axes featuring different packing schemes. This reveals that the fission process strongly depends on the intermol. coupling: slip-stacking favors delocalization of excitations and allows for efficient exciton fission, while face-to-edge mol. orientations commonly found in the prevailing herringbone mol. stacking patterns even suppress it. The controversially debated role of excimer states as intermediary rather than competitive or precursory is clarified. The findings serve as a guideline for the design of next-generation mol. materials for application in future org. light-harvesting devices exploiting singlet exciton fission.
- 32Fujii, K.; Himcinschi, C.; Toader, M.; Kera, S.; Zahn, D.; Ueno, N. Vibrational Properties of Perfluoropentacene Thin Film. J. Electron Spectrosc. Relat. Phenom. 2009, 174 (1–3), 65– 69, DOI: 10.1016/j.elspec.2009.01.002Google ScholarThere is no corresponding record for this reference.
- 33Salzmann, I.; Moser, A.; Oehzelt, M.; Breuer, T.; Feng, X. L.; Juang, Z. Y.; Nabok, D.; Della Valle, R. G.; Duhm, S.; Heimel, G. Epitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated Quartz. ACS Nano 2012, 6 (12), 10874– 10883, DOI: 10.1021/nn3042607Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs1Ons7%252FO&md5=6ebffad7140d6f872e989c6e7bfd1f0bEpitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated QuartzSalzmann, Ingo; Moser, Armin; Oehzelt, Martin; Breuer, Tobias; Feng, Xinliang; Juang, Zhen-Yu; Nabok, Dmitrii; Della Valle, Raffaele G.; Duhm, Steffen; Heimel, Georg; Brillante, Aldo; Venuti, Elisabetta; Bilotti, Ivano; Christodoulou, Christos; Frisch, Johannes; Puschnig, Peter; Draxl, Claudia; Witte, Gregor; Muellen, Klaus; Koch, NorbertACS Nano (2012), 6 (12), 10874-10883CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Chem.-vapor-deposited large-area graphene is employed as the coating of transparent substrates for the growth of the prototypical org. n-type semiconductor perfluoropentacene (PFP). The graphene coating is found to cause face-on growth of PFP in a yet unknown substrate-mediated polymorph, which is solved by combining grazing-incidence X-ray diffraction with theor. structure modeling. In contrast to the otherwise common herringbone arrangement of PFP in single crystals and "standing" films, the authors report a π-stacked arrangement of coplanar mols. in "flat-lying" films, which exhibit an exceedingly low π-stacking distance of only 3.07 Å, giving rise to significant electronic band dispersion along the π-stacking direction, as evidenced by UPS. The study underlines the high potential of graphene for use as a transparent electrode in (opto-)electronic applications, where optimized vertical transport through flat-lying conjugated org. mols. is desired.
- 34Zeiser, C.; Moretti, L.; Geiger, T.; Kalix, L.; Valencia, A. M.; Maiuri, M.; Cocchi, C.; Bettinger, H. F.; Cerullo, G.; Broch, K. Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene. J. Phys. Chem. Lett. 2021, 12 (31), 7453– 7458, DOI: 10.1021/acs.jpclett.1c01805Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhs1OlsLfJ&md5=f7b100501a52a512cde993994253db60Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in PentaceneZeiser, Clemens; Moretti, Luca; Geiger, Thomas; Kalix, Lukas; Valencia, Ana M.; Maiuri, Margherita; Cocchi, Caterina; Bettinger, Holger F.; Cerullo, Giulio; Broch, KatharinaJournal of Physical Chemistry Letters (2021), 12 (31), 7453-7458CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Singlet fission (SF), the photophys. process in which 1 singlet exciton is transformed into 2 triplets, depends inter alia on the coupling of electronic states. Here, the authors use fluorination and the resulting changes in partial charge distribution across the chromophore backbone as a particularly powerful tool to control this parameter in pentacene. The introduction of a permanent dipole moment leads to an enhanced coupling of Frenkel exciton and charge transfer states and to an increased SF rate which the authors probed using ultrafast transient absorption spectroscopy. These findings are contrasted with H-aggregate formation and a significantly reduced triplet-pair state lifetime in a fluorinated pentacene for which the different partial charge distribution leads to a negligible dipole moment.
- 35Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.; Inoue, Y.; Sato, F.; Tokito, S. Perfluoropentacene: High-Performance P–N Junctions and Complementary Circuits with Pentacene. JACS. 2004, 126 (26), 8138– 8140, DOI: 10.1021/ja0476258Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXkvVSjtb4%253D&md5=7a1df958b075ea8c06255f123a8f5fddPerfluoropentacene: High-Performance p-n Junctions and Complementary Circuits with PentaceneSakamoto, Youichi; Suzuki, Toshiyasu; Kobayashi, Masafumi; Gao, Yuan; Fukai, Yasushi; Inoue, Youji; Sato, Fumio; Tokito, ShizuoJournal of the American Chemical Society (2004), 126 (26), 8138-8140CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report the synthesis and characterization of perfluoropentacene as an n-type semiconductor for org. field-effect transistors (OFETs). Perfluoropentacene is a planar and cryst. material that adopts a herringbone structure as obsd. for pentacene. OFETs with perfluoropentacene were constructed using top-contact geometry, and an electron mobility of 0.11 cm2 V-1 s-1 was obsd. Bipolar OFETs with perfluoropentacene and pentacene function at both neg. and pos. gate voltages. The improved p-n junctions are probably due to the similar d-spacings of both acenes. Complementary inverter circuits were fabricated, and the transfer characteristics exhibit a sharp inversion of the output signal with a high-voltage gain.
- 36Timmer, D.; Gittinger, M.; Quenzel, T.; Cadore, A. R.; Rosa, B. L. T.; Li, W. S.; Soavi, G.; Lünemann, D. C.; Stephan, S.; Silies, M. Ultrafast Coherent Exciton Couplings and Many-Body Interactions in Monolayer WS. Nano Lett. 2024, 24, 8117– 8125, DOI: 10.1021/acs.nanolett.4c01991Google ScholarThere is no corresponding record for this reference.
- 37Timmer, D.; Lünemann, D. C.; Riese, S.; Sio, A. D.; Lienau, C. Full Visible Range Two-Dimensional Electronic Spectroscopy with High Time Resolution. Opt. Express 2024, 32 (1), 835– 847, DOI: 10.1364/OE.511906Google ScholarThere is no corresponding record for this reference.
- 38Timmer, D.; Gittinger, M.; Quenzel, T.; Stephan, S.; Zhang, Y.; Schumacher, M. F.; Lützen, A.; Silies, M.; Tretiak, S.; Zhong, J.-H. Plasmon Mediated Coherent Population Oscillations in Molecular Aggregates. Nat. Commun. 2023, 14 (1), 8035, DOI: 10.1038/s41467-023-43578-4Google ScholarThere is no corresponding record for this reference.
- 39Quenzel, T.; Timmer, D.; Gittinger, M.; Zablocki, J.; Zheng, F. L.; Schiek, M.; Lutzen, A.; Frauenheim, T.; Tretiak, S.; Silies, M. Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates. ACS Nano 2022, 16 (3), 4693– 4704, DOI: 10.1021/acsnano.1c11398Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xkt1Churc%253D&md5=96f3e1e23894b2d637fb580f697d5a8ePlasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular AggregatesQuenzel, Thomas; Timmer, Daniel; Gittinger, Moritz; Zablocki, Jennifer; Zheng, Fulu; Schiek, Manuela; Luetzen, Arne; Frauenheim, Thomas; Tretiak, Sergei; Silies, Martin; Zhong, Jin-Hui; De Sio, Antonietta; Lienau, ChristophACS Nano (2022), 16 (3), 4693-4704CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Enlarging exciton coherence lengths in mol. aggregates is crit. for enhancing the collective optical and transport properties of mol. thin film nanostructures or devices. We demonstrate that the exciton coherence length of squaraine aggregates can be increased from 10 to 24 mol. units at room temp. when prepg. the aggregated thin film on a metallic rather than a dielec. substrate. Two-dimensional electronic spectroscopy measurements reveal a much lower degree of inhomogeneous line broadening for aggregates on a gold film, pointing to a reduced disorder. The result is corroborated by simulations based on a Frenkel exciton model including exciton-plasmon coupling effects. The simulation shows that localized, energetically nearly resonant excitons on spatially well sepd. segments can be radiatively coupled via delocalized surface plasmon polariton modes at a planar mol.-gold interface. Such plasmon-enhanced delocalization of the exciton wave function is of high importance for improving the coherent transport properties of mol. aggregates on the nanoscale. Addnl., it may help tailor the collective optical response of org. materials for quantum optical applications.
- 40Timmer, D.; Zheng, F.; Gittinger, M.; Quenzel, T.; Lünemann, D. C.; Winte, K.; Zhang, Y.; Madjet, M. E.; Zablocki, J.; Lützen, A. Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes. JACS. 2022, 144 (41), 19150– 19162, DOI: 10.1021/jacs.2c08682Google ScholarThere is no corresponding record for this reference.
- 41Breuer, T. Preparation and Characterization of Thin Films of Organic Semiconductors and their Heterostructures. Ph.D. Thesis, University of Marburg, Marburg, Germany, 2013.Google ScholarThere is no corresponding record for this reference.
- 42Cocchi, C.; Breuer, T.; Witte, G.; Draxl, C. Polarized Absorbance and Davydov Splitting in Bulk and Thin-Film Pentacene Polymorphs. Phys. Chem. Chem. Phys. 2018, 20 (47), 29724– 29736, DOI: 10.1039/C8CP06384BGoogle Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitFyqs7zF&md5=efa3e8bbcf27be2c0e51a7f01ae72b80Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphsCocchi, Caterina; Breuer, Tobias; Witte, Gregor; Draxl, ClaudiaPhysical Chemistry Chemical Physics (2018), 20 (47), 29724-29736CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Pentacene is one of the most studied org. materials and in particular its optical properties have been the subject of intense research during the last two decades. In spite of such a widespread interest and of the extensive knowledge achieved so far, a no. of issues are still debated. One of the most relevant questions concerns the role of polymorphism and how it affects the lowest-energy exciton, which appears in the visible region and is subject to a sizable Davydov splitting. We address this problem in a combined theor. and exptl. work, where the optical absorption properties of three pentacene polymorphs are investigated within the whole energy range of visible light. Optical spectra computed from first principles in the framework of many-body perturbation theory are directly compared with the polarization-resolved absorbance, measured for three different pentacene phases (the two bulk polymorphs and the thin-film phase). In this way, we unambiguously identify the two Davydov components of the first exciton and the optical fingerprints of each considered phase. With very good agreement between theory and expt., we show that all polymorphs exhibit common features at the absorption onset, while phase-dependent characteristics appear only above 2 eV. We discuss the character of the lowest-lying singlet and triplet excitons, including dark ones, highlighting the contributions from the electronic bands and the role of the electron-hole interaction and of the local-field effects.
- 43Kumar, A. T. N.; Rosca, F.; Widom, A.; Champion, P. M. Investigations of Amplitude and Phase Excitation Profiles in Femtosecond Coherence Spectroscopy. J. Chem. Phys. 2001, 114 (2), 701– 724, DOI: 10.1063/1.1329640Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXmvFKr&md5=eb42607c979c7f4e908aa9811d92261fInvestigations of amplitude and phase excitation profiles in femtosecond coherence spectroscopyKumar, Anand T. N.; Rosca, Florin; Widom, Allan; Champion, Paul M.Journal of Chemical Physics (2001), 114 (2), 701-724CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)We present an effective linear response approach to pump-probe femtosecond coherence spectroscopy in the well-sepd. pulse limit. The treatment presented here is based on a displaced and squeezed state representation for the nonstationary states induced by an ultrashort pump laser pulse or a chem. reaction. The subsequent response of the system to a delayed probe pulse is modeled using closed form nonstationary linear response functions, valid for a multimode vibronically coupled system at arbitrary temp. When pump-probe signals are simulated using the linear response functions, with the mean nuclear positions and momenta obtained from a rigorous moment anal. of the pump induced (doorway) state, the signals are found to be in excellent agreement with the conventional third-order response approach. The key advantages offered by the moment anal.-based linear response approach include a clear phys. interpretation of the amplitude and phase of oscillatory pump-probe signals, a dramatic improvement in computation times, a direct connection between pump-probe signals and equil. absorption and dispersion lineshapes, and the ability to incorporate coherence assocd. with rapid nonradiative surface crossing. We demonstrate these aspects using numerical simulations, and also apply the present approach to the interpretation of exptl. amplitude and phase measurements on reactive and nonreactive samples of the heme protein myoglobin. The role played by inhomogeneous broadening in the obsd. amplitude and phase profiles is discussed in detail. We also investigate overtone signals in the context of reaction driven coherent motion.
- 44Nguyen, X. T.; Winte, K.; Timmer, D.; Rakita, Y.; Ceratti, D. R.; Aharon, S.; Ramzan, M. S.; Cocchi, C.; Lorke, M.; Jahnke, F. Phonon-Driven Intra-Exciton Rabi Oscillations in CsPbBr3 Halide Perovskites. Nat. Commun. 2023, 14 (1), 1047, DOI: 10.1038/s41467-023-36654-2Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXkt1OhsbY%253D&md5=170be8d47fd8df691bd7fcc8f5d19d42Phonon-driven intra-exciton Rabi oscillations in CsPbBr3 halide perovskitesNguyen, Xuan Trung; Winte, Katrin; Timmer, Daniel; Rakita, Yevgeny; Ceratti, Davide Raffaele; Aharon, Sigalit; Ramzan, Muhammad Sufyan; Cocchi, Caterina; Lorke, Michael; Jahnke, Frank; Cahen, David; Lienau, Christoph; De Sio, AntoniettaNature Communications (2023), 14 (1), 1047CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)Coupling electromagnetic radiation with matter, e.g., by resonant light fields in external optical cavities, is highly promising for tailoring the optoelectronic properties of functional materials on the nanoscale. Here, we demonstrate that even internal fields induced by coherent lattice motions can be used to control the transient excitonic optical response in CsPbBr3 halide perovskite crystals. Upon resonant photoexcitation, two-dimensional electronic spectroscopy reveals an excitonic peak structure oscillating persistently with a 100-fs period for up to ≈2 ps which does not match the frequency of any phonon modes of the crystals. Only at later times, beyond 2 ps, two low-frequency phonons of the lead-bromide lattice dominate the dynamics. We rationalize these findings by an unusual exciton-phonon coupling inducing off-resonant 100-fs Rabi oscillations between 1s and 2p excitons driven by the low-frequency phonons. As such, prevailing models for the electron-phonon coupling in halide perovskites are insufficient to explain these results. We propose the coupling of characteristic low-frequency phonon fields to intra-excitonic transitions in halide perovskites as the key to control the anharmonic response of these materials in order to establish new routes for enhancing their optoelectronic properties.
- 45Polli, D.; Antognazza, M. R.; Brida, D.; Lanzani, G.; Cerullo, G.; De Silvestri, S. Broadband Pump-Probe Spectroscopy with Sub-10-fs Resolution for Probing Ultrafast Internal Conversion and Coherent Phonons in Carotenoids. Chem. Phys. 2008, 350 (1–3), 45– 55, DOI: 10.1016/j.chemphys.2007.12.021Google ScholarThere is no corresponding record for this reference.
- 46Andrzejak, M.; Mazur, G.; Musser, A. J.; Petelenz, P.; Skóra, T. Properties of Coherent Vibrational Wavepackets Critically Depend on the Method of Their Generation. J. Phys. Chem. C 2024, 128 (24), 9837– 9846, DOI: 10.1021/acs.jpcc.4c01485Google ScholarThere is no corresponding record for this reference.
- 47Albrecht, A. C. Theory of Raman Intensities. J. Chem. Phys. 1961, 34 (5), 1476– 1484, DOI: 10.1063/1.1701032Google ScholarThere is no corresponding record for this reference.
- 48Ruhman, S.; Joly, A. G.; Nelson, K. A. Coherent Molecular Vibrational Motion Observed in the Time Domain Through Impulsive Stimulated Raman-Scattering. IEEE J. Quantum Electron. 1988, 24 (2), 460– 469, DOI: 10.1109/3.146Google ScholarThere is no corresponding record for this reference.
- 49Banin, U.; Bartana, A.; Ruhman, S.; Kosloff, R. Impulsive Excitation of Coherent Vibrational Motion Ground Surface Dynamics Induced by Intense Short Pulses. J. Chem. Phys. 1994, 101 (10), 8461– 8481, DOI: 10.1063/1.468108Google Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXjt1yis7g%253D&md5=b7e1321e28594dfc02e3760f790240a3Impulsive excitation of coherent vibrational motion ground surface dynamics induced by intense short pulsesBanin, Uri; Bartana, Allon; Ruhman, Sanford; Kosloff, RonnieJournal of Chemical Physics (1994), 101 (10), 8461-81CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)A framework for understanding impulsively photoinduced vibrational coherent motion on the ground electronic surface is presented. In particular strong resonant excitation to a directly dissociative electronic surface is considered. Three distinct approaches are employed. A two surface Fourier wavepacket method explicitly including the field explores this process in isolated mols. A coordinate dependent two-level system is employed to develop a novel anal. approx. to the photoinduced quantum dynamics. The negligible computational requirements make it a powerful interactive tool for reconstructing the impulsive photoexcitation stage. Its anal. nature provides closed from expressions for the photoinduced changes in the material. Finally the full simulation of the process including the solvent effects is carried out by a numerical propagation of the d. operator. In all three techniques the excitation field is treated to all orders, allowing an anal. of current expts. using strong fields, resulting in substantial photoconversion. The emerging picture is that the impulsive excitation carves a coherent dynamic "hole" out of the ground surface d. A rigorous definition of the dynamic "hole" is constructed and used to define a measure of its coherence. In particular all photoinduced time dependence in the system can be directly related to the dynamic "hole". All three techniques are used to simulate the pump probe expt. on the sym. stretch mode of I3-3, including electronic and vibrational dephasing.
- 50Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119, 9506, DOI: 10.1021/acs.jpca.5b05948Google Scholar50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlSmt7rJ&md5=0099060f0280493b160d6570da65c8dePrinciples and Applications of Broadband Impulsive Vibrational SpectroscopyLiebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
- 51Rather, S. R.; Fu, B.; Kudisch, B.; Scholes, G. D. Interplay of Vibrational Wavepackets during an Ultrafast Electron Transfer Reaction. Nat. Chem. 2021, 13 (1), 70– 76, DOI: 10.1038/s41557-020-00607-9Google ScholarThere is no corresponding record for this reference.
- 52Liebel, M.; Schnedermann, C.; Kukura, P. Vibrationally Coherent Crossing and Coupling of Electronic States during Internal Conversion in β-Carotene. Phys. Rev. Lett. 2014, 112 (19), 198302, DOI: 10.1103/PhysRevLett.112.198302Google Scholar52https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Omsr7O&md5=2503b25a9cbbd8f5f8478ee18be59759Vibrationally coherent crossing and coupling of electronic states during internal conversion in β-caroteneLiebel, M.; Schnedermann, C.; Kukura, P.Physical Review Letters (2014), 112 (19), 198302/1-198302/5, 5 pp.CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Coupling of nuclear and electronic degrees of freedom mediates energy flow in mols. after optical excitation. The assocd. coherent dynamics in polyat. systems, however, remain exptl. unexplored. Here, we combined transient absorption spectroscopy with electronic population control to reveal nuclear wave packet dynamics during the S2 → S1 internal conversion in β-carotene. We show that passage through a conical intersection is vibrationally coherent and thereby provides direct feedback on the role of different vibrational coordinates in the breakdown of the Born-Oppenheimer approxn.
- 53Falke, S. M.; Rozzi, C. A.; Brida, D.; Maiuri, M.; Amato, M.; Sommer, E.; De Sio, A.; Rubio, A.; Cerullo, G.; Molinari, E. Coherent Ultrafast Charge Transfer in an Organic Photovoltaic Blend. Science 2014, 344 (6187), 1001– 1005, DOI: 10.1126/science.1249771Google Scholar53https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXosFSmur0%253D&md5=07e4c1b7dbaf8e4bf8d63a4d190a98e7Coherent ultrafast charge transfer in an organic photovoltaic blendFalke, Sarah Maria; Rozzi, Carlo Andrea; Brida, Daniele; Maiuri, Margherita; Amato, Michele; Sommer, Ephraim; De Sio, Antonietta; Rubio, Angel; Cerullo, Giulio; Molinari, Elisa; Lienau, ChristophScience (Washington, DC, United States) (2014), 344 (6187), 1001-1005CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Blends of conjugated polymers and fullerene derivs. are prototype systems for org. photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, the authors elucidate the initial quantum dynamics of this process. Exptl., the authors obsd. coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with 1st-principle theor. simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-fs period matching that of the obsd. vibrational modes. The authors' results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound ref. system.
- 54Orlandi, G.; Siebrand, W. Theory of Vibronic Intensity Borrowing - Comparison of Herzberg-Teller and Born-Oppenheimer Coupling. J. Chem. Phys. 1973, 58 (10), 4513– 4523, DOI: 10.1063/1.1679014Google ScholarThere is no corresponding record for this reference.
- 55Avila Ferrer, F. J.; Barone, V.; Cappelli, C.; Santoro, F. Duschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of Pyrene. J. Chem. Theory. Comput. 2013, 9 (8), 3597– 3611, DOI: 10.1021/ct400197yGoogle Scholar55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXpsFGmtb0%253D&md5=4f68741ea896d01b5efffe08c008b3aeDuschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of PyreneAvila Ferrer, Francisco J.; Barone, Vincenzo; Cappelli, Chiara; Santoro, FabrizioJournal of Chemical Theory and Computation (2013), 9 (8), 3597-3611CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)A recently developed time-independent approach for the calcn. of vibrational resonance Raman (vRR) spectra is able to describe Duschinsky and Herzberg-Teller (HT) effects acting on a single resonant state, together with interferential contributions arising from multiple electronic resonances, allowing one to study in detail how their interplay dets. both the vRR spectra at selected wavelengths and the Raman excitation profiles. The authors apply this methodol. to the study of the spectra of pyrene in MeCN, an ideal system since it exhibits 3 close-lying electronic transitions that are bright but also subjected to HT effects. To single out the different contributions to vRR line shapes the authors adopted 2 different adiabatic models for resonant-state potential energy surfaces, namely, Adiabatic Shift (only accounting from equil. geometry displacements) and Adiabatic Hessian (AH, including also the Duschinsky effects), and Franck-Condon (FC) or HT approxns. for the transition dipole. On balance, FC+HT calcns. within the AH model provide the best agreement with expt. Also, the methodol. permits to individuate bands in the exptl. spectra due to the simultaneous contribution of >1 resonant state and to point out and analyze interferential effects between the FC and HT terms in each resonance Raman process, together with FC-HT and HT-HT interferences between different electronic states.
- 56Petelenz, P.; Andrzejak, M. Vibronic Interpretation of the Low-Energy Absorption Spectrum of the Sexithiophene Single Crystal. J. Chem. Phys. 2000, 113 (24), 11306– 11314, DOI: 10.1063/1.1290026Google ScholarThere is no corresponding record for this reference.
- 57Witkowski, A.; Moffitt, W. Electronic Spectra of Dimers - Derivation of the Fundamental Vibronic Equations. J. Chem. Phys. 1960, 33 (3), 872– 875, DOI: 10.1063/1.1731278Google ScholarThere is no corresponding record for this reference.
- 58Zgierski, M. Z.; Pawlikowski, M. Absorption and Circular-Dichroism Spectra of Dimeric Systems - Extended Dimer Model. J. Chem. Phys. 1983, 79 (4), 1616– 1633, DOI: 10.1063/1.446033Google ScholarThere is no corresponding record for this reference.
- 59Bizimana, L. A.; Carbery, W. P.; Gellen, T. A.; Turner, D. B. Signatures of Herzberg-Teller Coupling in Three-Dimensional Electronic Spectroscopy. J. Chem. Phys. 2017, 146 (8), 084311, DOI: 10.1063/1.4976995Google ScholarThere is no corresponding record for this reference.
- 60Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77 (18), 3865– 3868, DOI: 10.1103/PhysRevLett.77.3865Google Scholar60https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XmsVCgsbs%253D&md5=55943538406ee74f93aabdf882cd4630Generalized gradient approximation made simplePerdew, John P.; Burke, Kieron; Ernzerhof, MatthiasPhysical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
- 61Günder, D.; Valencia, A. M.; Guerrini, M.; Breuer, T.; Cocchi, C.; Witte, G. Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN: PFP Cocrystalline Films: Limits of Nonperiodic Modeling. J. Phys. Chem. Lett. 2021, 12 (40), 9899– 9905, DOI: 10.1021/acs.jpclett.1c02761Google ScholarThere is no corresponding record for this reference.
- 62Valencia, A. M.; Bischof, D.; Anhäuser, S.; Zeplichal, M.; Terfort, A.; Witte, G.; Cocchi, C. Excitons in Organic Materials: Revisiting Old Concepts with New Insights. Electron. Struct. 2023, 5 (3), 033003, DOI: 10.1088/2516-1075/acf2d4Google ScholarThere is no corresponding record for this reference.
- 63Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119 (36), 9506– 9517, DOI: 10.1021/acs.jpca.5b05948Google Scholar63https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlSmt7rJ&md5=0099060f0280493b160d6570da65c8dePrinciples and Applications of Broadband Impulsive Vibrational SpectroscopyLiebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
- 64Lanzani, G.; Cerullo, G.; De Silvestri, S. Coherent Vibrational Dynamics; CRC Press, 2007.Google ScholarThere is no corresponding record for this reference.
- 65Grupp, A.; Budweg, A.; Fischer, M. P.; Allerbeck, J.; Soavi, G.; Leitenstorfer, A.; Brida, D. Broadly Tunable Ultrafast Pump-Probe System Operating at Multi-kHz Repetition Rate. J. Opt. 2018, 20 (1), 014005, DOI: 10.1088/2040-8986/aa9b07Google ScholarThere is no corresponding record for this reference.
- 66Brida, D.; Manzoni, C.; Cerullo, G. Phase-Locked Pulses for Two-Dimensional Spectroscopy by a Birefringent Delay Line. Opt. Lett. 2012, 37 (15), 3027– 3029, DOI: 10.1364/OL.37.003027Google Scholar66https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC38flt1Sqsg%253D%253D&md5=774e1891ccbfb9f8581dab50436ee22ePhase-locked pulses for two-dimensional spectroscopy by a birefringent delay lineBrida Daniele; Manzoni Cristian; Cerullo GiulioOptics letters (2012), 37 (15), 3027-9 ISSN:.We introduce the translating wedge-based identical pulses encoding system, a novel device for the generation of collinear, interferometrically locked ultrashort pulse pairs. By means of birefringent wedges, we are able to control the pulse delay with attosecond precision and stability better that λ/360, without affecting the pulse duration and in a spectral range that spans from UV to mid-IR. This device is expected to dramatically simplify two-dimensional spectroscopy experiments.
- 67Frisch, M. e.; Trucks, G.; Schlegel, H. B.; Scuseria, G.; Robb, M.; Cheeseman, J.; Scalmani, G.; Barone, V.; Petersson, G.; Nakatsuji, H. Gaussian 16; Gaussian, Inc.: Wallingford, CT, 2016.Google ScholarThere is no corresponding record for this reference.
- 68Lee, S. Y.; Heller, E. J. Time-Dependent Theory of Raman Scattering. J. Chem. Phys. 1979, 71 (12), 4777– 4788, DOI: 10.1063/1.438316Google Scholar68https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3cXms12ltA%253D%253D&md5=4233d1d72a3c69c20cb74a9e7c27ef2aTime-dependent theory of Raman scatteringLee, Soo-Y.; Heller, E. J.Journal of Chemical Physics (1979), 71 (12), 4777-88CODEN: JCPSA6; ISSN:0021-9606.A time-dependent picture of vibrational Raman scattering in the weak field limit is presented. From this viewpoint the static effects, due to the coordinate dependence of the electronic transition dipole, can be sepd. from the dynamic effects that arise from wave packet propagation on the Born-Oppenheimer surfaces. Away from resonance, the energy uncertainty relation gives the propagation time necessary to obtain the cross section as being inversely proportional to the mismatch of the excitation frequency with the excited surface. The wave packet, given by the initial vibrational wave function times the transition dipole, hardly moves on the excited surface when the excitation frequency is far from resonance. As the excitation frequency is tuned closer to resonance, the propagated wave packet samples a larger portion of the surface. By using the short time approxn. to the propagator, formulas were obtained for the cross section that are applicable for Raman scattering by polyatomics. The short time approxn. is expected to be good away from resonance independent of the nature of the surface, and also on resonance with a repulsive surface. For an attractive surface, the approxn. gives the av. resonant cross section useful in the case when the vibrational structures cannot be obsd.
- 69Porezag, D.; Pederson, M. R. Infrared Intensities and Raman-Scattering Activities Within Density-Functional Theory. Phys. Rev. B 1996, 54 (11), 7830, DOI: 10.1103/PhysRevB.54.7830Google Scholar69https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XmtVWrtb0%253D&md5=284a618dbda84734a287f7affa0eea2bInfrared intensities and Raman-scattering activities within density-functional theoryPorezag, Dirk; Pederson, Mark R.Physical Review B: Condensed Matter (1996), 54 (11), 7830-7836CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)The computational complexity assocd. with the d.-functional-based detn. of IR intensities and nonresonant Raman scattering activities is the same as that required for vibrational modes. Further, the authors use extremely large basis sets to det. the intrinsic accuracy for calcg. such phenomena within the d.-functional theory. The authors present benchmark calcns. on CH4, H2O, C2H2, C2H4, and C2H6 within both the local-d. approxn. (LDA) and the generalized gradient approxn. (GGA). Tests of the reliability and numerical stability of the theor. scheme are presented. To obtain reliable results, appropriate polarization basis functions and well-converged wave functions are necessary. While most of the Raman spectra predicted by LDA agree very well with exptl. data, some of the IR intensities show substantial errors. The GGA functional overcomes most of these deficiencies, leading to an overall good agreement with expt.
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- 1Klauk, H. Organic Electronics: Materials, Manufacturing and Applications; Wiley-VCH, 2006.There is no corresponding record for this reference.
- 2Brédas, J. L.; Marder, S. R. The WSPC Reference on Organic Electronics: Organic Semiconductors; World Scientific, 2016.There is no corresponding record for this reference.
- 3Ostroverkhova, O. Organic Optoelectronic Materials: Mechanisms and Applications. Chem. Rev. 2016, 116 (22), 13279– 13412, DOI: 10.1021/acs.chemrev.6b001273https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xhs1egsLnM&md5=4ab815e1951d3749bf2a5bbd93106a9bOrganic Optoelectronic Materials: Mechanisms and ApplicationsOstroverkhova, OksanaChemical Reviews (Washington, DC, United States) (2016), 116 (22), 13279-13412CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Org. (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technol. promises include low cost of these materials and the possibility of their room-temp. deposition from soln. on large-area and/or flexible substrates. The article reviews the current understanding of the phys. mechanisms that det. the (opto)electronic properties of high-performance org. materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Addnl., it highlights the capabilities of various exptl. techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small mols. and on conjugated polymers are considered, and their applications in org. solar cells, photodetectors, and photorefractive devices are discussed.
- 4Rand, B. P.; Cheyns, D.; Vasseur, K.; Giebink, N. C.; Mothy, S.; Yi, Y.; Coropceanu, V.; Beljonne, D.; Cornil, J.; Brédas, J.-L. The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction. Adv. Funct. Mater. 2012, 22 (14), 2987– 2995, DOI: 10.1002/adfm.2012005124https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xls1elsr4%253D&md5=8bf9b0dffbdcb55f4bf37f16b543b34bThe Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene HeterojunctionRand, Barry P.; Cheyns, David; Vasseur, Karolien; Giebink, Noel C.; Mothy, Sebastien; Yi, Yuanping; Coropceanu, Vaeceslav; Beljonne, David; Cornil, Jerome; Bredas, Jean-Luc; Genoe, JanAdvanced Functional Materials (2012), 22 (14), 2987-2995CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)The anisotropy inherent to many planar org. mols. leads to a high sensitivity of various fundamental processes to the orientation of mols. within films and at heterojunctions. Such processes include absorption, charge and exciton transport, energy levels, and charge transfer, all of which are crit. to org. solar cell operation. Here,an in-depth study of bilayer cells consisting of a donor/acceptor interface between zinc phthalocyanine (ZnPc) and fullerene (C60) is conducted and devices with the typically deposited standing up (edge-on) orientation are compared to those with ZnPc lying flat (face-on). The face-on ZnPc-based device allows for an increase in all solar cell parameters, substantially increasing power conversion efficiency from 1.5% to 2.8%. Spectrally resolved photocurrent measurements reveal a >50% increase in ZnPc signal, from which only 12% is accounted for by the increase in absorption assocd. with the face-on orientation. The increase in internal quantum efficiency is accounted for via an improved charge transfer. The results of this study indicate that proper consideration of the orientation between donor and acceptor needs to be taken to fully optimize the numerous processes required for photovoltaic energy conversion.
- 5Karl, N. Charge Carrier Transport in Organic Semiconductors. Synth. Met. 2003, 133–134, 649– 657, DOI: 10.1016/S0379-6779(02)00398-35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXhvFWhu78%253D&md5=ff758217b810ffedeeb3ce430c424a52Charge carrier transport in organic semiconductorsKarl, N.Synthetic Metals (2003), 133-134 (), 649-657CODEN: SYMEDZ; ISSN:0379-6779. (Elsevier Science B.V.)A review. To understand charge carrier transport in org. semiconductors the magnitude and anisotropy, as well as the temp. and eventual elec. field dependence of the electron and of the hole mobility are fundamental parameters. A no. of tech. applications require high mobilities. A brief review is given on different exptl. methods that can either directly measure charge carrier mobilities, or at least lead to an est. For high purity single crystals, a steep increase of mobilities towards low temp. with the consequence of nonlinear transport and final velocity satn. at elevated elec. fields was found and traced back to temp.-dependent electron and hole masses approaching the free electron mass at low temp. This, and addnl. recent reports in literature on ultrahigh mobilities-with a no. of exciting consequences, such as integer and fractional quantum Hall effect and even supercond. in such materials as anthracene, tetracene, pentacene, and C60-are clear indications of band transport. With rising temp. electron-phonon coupling, and therefore the effective masses, increase and coherent band transport is gradually destroyed; polaron-hopping transport evolves as a parallel channel and dominates at sufficiently high temp. For crystals with orientational disorder of the mols. band transport is precluded.
- 6Podzorov, V.; Menard, E.; Borissov, A.; Kiryukhin, V.; Rogers, J. A.; Gershenson, M. E. Intrinsic Charge Transport on the Surface of Organic Semiconductors. Phys. Rev. Lett. 2004, 93 (8), 086602, DOI: 10.1103/PhysRevLett.93.0866026https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXmvVCmu70%253D&md5=0c17a1860622a0c0b61a44b8fd2b2c86Intrinsic Charge Transport on the Surface of Organic SemiconductorsPodzorov, V.; Menard, E.; Borissov, A.; Kiryukhin, V.; Rogers, J. A.; Gershenson, M. E.Physical Review Letters (2004), 93 (8), 086602/1-086602/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)The air-gap field-effect technique enabled realization of the intrinsic (not limited by static disorder) polaronic transport on the surface of rubrene (C42H28) crystals over a wide temp. range. The signatures of this intrinsic transport are the anisotropy of the carrier mobility, μ, and the growth of μ with cooling. Anisotropy of μ vanishes in the activation regime at low temps., where the transport is dominated by shallow traps. The deep traps, introduced by x-ray radiation, increase the field-effect threshold without affecting μ, an indication that the filled traps do not scatter polarons.
- 7Repp, J.; Liljeroth, P.; Meyer, G. Coherent Electron–Nuclear Coupling in Oligothiophene Molecular Wires. Nat. Phys. 2010, 6 (12), 975– 979, DOI: 10.1038/nphys1802There is no corresponding record for this reference.
- 8Du, S.; Yoshida, K.; Zhang, Y.; Hamada, I.; Hirakawa, K. Terahertz Dynamics of Electron–Vibron Coupling in Single Molecules with Tunable Electrostatic Potential. Nat. Photonics. 2018, 12 (10), 608– 612, DOI: 10.1038/s41566-018-0241-18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhs1ekur3P&md5=454dfe31e3c065882c1523c97dd1ee90Terahertz dynamics of electron-vibron coupling in single molecules with tunable electrostatic potentialDu, Shaoqing; Yoshida, Kenji; Zhang, Ya; Hamada, Ikutaro; Hirakawa, KazuhikoNature Photonics (2018), 12 (10), 608-612CODEN: NPAHBY; ISSN:1749-4885. (Nature Research)Clarifying electronic and vibronic properties at the individual mol. level provides key insights for future chem., nanoelectronics and quantum information technologies. However, information obtained by conventional single-mol. transport measurements is based on time-averaged properties. Here, we report on terahertz (THz) spectroscopy of single fullerene mols. by using a single-mol. transistor geometry. From the time-domain THz autocorrelation measurements, we obtained THz spectra assocd. with the THz-induced center-of-mass oscillation of the mols. The obsd. spectra reflect the potential profile experienced by the mol. on the metal surface when the no. of electrons on the mol. fluctuates by one during the single-electron tunnelling process. Such an ultra-high sensitivity to the electronic/vibronic structures of a single mol. on the addn./removal of a single electron has been achieved as a result of using THz spectroscopy in the single-mol. transistor geometry. This scheme provides an opportunity to investigate the ultrafast THz dynamics of subnanometre-scale systems.
- 9Kong, F.-F.; Tian, X.-J.; Zhang, Y.; Yu, Y.-J.; Jing, S.-H.; Zhang, Y.; Tian, G.-J.; Luo, Y.; Yang, J.-L.; Dong, Z.-C. Probing Intramolecular Vibronic Coupling Through Vibronic-State Imaging. Nat. Commun. 2021, 12 (1), 1280, DOI: 10.1038/s41467-021-21571-z9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXltFyjtbc%253D&md5=18a8a79f82b02092f23ca52bc5d85e49Probing intramolecular vibronic coupling through vibronic-state imagingKong, Fan-Fang; Tian, Xiao-Jun; Zhang, Yang; Yu, Yun-Jie; Jing, Shi-Hao; Zhang, Yao; Tian, Guang-Jun; Luo, Yi; Yang, Jin-Long; Dong, Zhen-Chao; Hou, J. G.Nature Communications (2021), 12 (1), 1280CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)Vibronic coupling is a central issue in mol. spectroscopy. Here we investigate vibronic coupling within a single pentacene mol. in real space by imaging the spatial distribution of single-mol. electroluminescence via highly localized excitation of tunneling electrons in a controlled plasmonic junction. The obsd. two-spot orientation for certain vibronic-state imaging is found to be evidently different from the purely electronic 0-0 transition, rotated by 90°, which reflects the change in the transition dipole orientation from along the mol. short axis to the long axis. Such a change reveals the occurrence of strong vibronic coupling assocd. with a large Herzberg-Teller contribution, going beyond the conventional Franck-Condon picture. The emergence of large vibration-induced transition charges oscillating along the long axis is found to originate from the strong dynamic perturbation of the anti-sym. vibration on those carbon atoms with large transition d. populations during electronic transitions.
- 10Breuer, T.; Witte, G. Epitaxial Growth of Perfluoropentacene Films with Predefined Molecular Orientation: A Route for Single-Crystal Optical Studies. Phys. Rev. B 2011, 83 (15), 155428, DOI: 10.1103/PhysRevB.83.155428There is no corresponding record for this reference.
- 11Condon, E. A Theory of Intensity Distribution in Band Systems. Phys. Rev. 1926, 28 (6), 1182– 1201, DOI: 10.1103/PhysRev.28.118211https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaB2sXovV2i&md5=e84d9659e9f76759fea0962e1208351eTheory of intensity distribution in band systemsCondon, EdwardPhysical Review (1926), 28 (), 1182-1201CODEN: PHRVAO; ISSN:0031-899X.There is no expanded citation for this reference.
- 12Spano, F. C. Excitons in Conjugated Oligomer Aggregates, Films, and Crystals. Annu. Rev. Phys. Chem. 2006, 57, 217– 243, DOI: 10.1146/annurev.physchem.57.032905.10455712https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XltVeitL8%253D&md5=fddfeef2747c00b6c24d72efeda40db7Excitons in conjugated oligomer aggregates, films, and crystalsSpano, Frank C.Annual Review of Physical Chemistry (2006), 57 (), 217-243CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)A review. Recent exptl. and theor. investigations of excitons in conjugated oligomer nanoaggregates, thin films, and crystals are reviewed. The review focuses on the technol. important unsubstituted oligo(phenylene vinylene)s (OPVn) and oligothiophenes (OTn), which exhibit side-by-side herringbone crystal packing. Many of the salient photophys. properties displayed by OPVn and OTn solid phases, including the large Davydov splitting, the rich variety of peaks due to vibronic coupling in both absorption and emission, and the unusual behavior of the emission origin, are accounted for in a model including excitonic coupling between mols., linear exciton-phonon coupling, and disorder.
- 13Wykes, M.; Parambil, R.; Beljonne, D.; Gierschner, J. Vibronic Coupling in Molecular Crystals: A Franck-Condon Herzberg-Teller Model of H-Aggregate Fluorescence Based on Quantum Chemical Cluster Calculations. J. Chem. Phys. 2015, 143 (11), 114116, DOI: 10.1063/1.493060613https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsFaqtLjF&md5=9f26b83ff73d3cf44a5328093adb771eVibronic coupling in molecular crystals: A Franck-Condon Herzberg-Teller model of H-aggregate fluorescence based on quantum chemical cluster calculationsWykes, M.; Parambil, R.; Beljonne, D.; Gierschner, J.Journal of Chemical Physics (2015), 143 (11), 114116/1-114116/12CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)Here, the authors present a general approach to treating vibronic coupling in mol. crystals based on atomistic simulations of large clusters. Such clusters comprise model aggregates treated at the quantum chem. level embedded within a realistic environment treated at the mol. mechanics level. As the authors calc. ground and excited state equil. geometries and vibrational modes of model aggregates, approach is able to capture effects arising from coupling to intermol. degrees of freedom, absent from existing models relying on geometries and normal modes of single mols. Using the geometries and vibrational modes of clusters, the authors are able to simulate the fluorescence spectra of aggregates for which the lowest excited state bears negligible oscillator strength (as is the case, e.g., ideal H-aggregates) by including both Franck-Condon (FC) and Herzberg-Teller (HT) vibronic transitions. The latter terms allow the adiabatic excited state of the cluster to couple with vibrations in a perturbative fashion via derivs. of the transition dipole moment along nuclear coordinates. While vibronic coupling simulations employing FC and HT terms are well established for single-mols., to knowledge this is the first time they are applied to mol. aggregates. Here, the authors apply this approach to the simulation of the low-temp. fluorescence spectrum of para-distyrylbenzene single-crystal H-aggregates and draw comparisons with coarse-grained Frenkel-Holstein approaches previously extensively applied to such systems. (c) 2015 American Institute of Physics.
- 14Small, G. J. Herzberg-Teller Vibronic Coupling and Duschinsky Effect. J. Chem. Phys. 1971, 54 (8), 3300, DOI: 10.1063/1.167534314https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3MXhtlanurc%253D&md5=10bcade6be96b2af4c49f62d254bde79Herzberg-Teller vibronic coupling and the Duschinsky effectSmall, Gerald J.Journal of Chemical Physics (1971), 54 (8), 3300-6CODEN: JCPSA6; ISSN:0021-9606.The assumption that the difference in compn., in terms of symmetry coordinates, between the normal vibrational motions of the ground and 1st excited state (Duschinsky effect) can be neglected in the Herzberg-Teller theory of absorption and fluorescence vibronic intensities is crit. examd. A theory of the Duschinsky effect is described which involves expansion of the potential energy of the fluorescent state in terms of the ground state normal coordinate displacements. Off-diagonal quadratic contributions arise in the expansion whenever there is a coupling between the crude Born-Oppenheimer electronic wavefunctions of the fluorescent and other excited states through 2 or more ground state normal motions of the same symmetry. The importance of the Duschinsky effect depends on the magnitudes of the Herzberg-Teller vibronic matrix elements and the frequency differences between the fundamentals which effect vibronic perturbations. Inclusion of the Duschinsky effect in the Herzberg-Teller theory for 2 or more nontotally symmetric perturbing vibrations introduces a constructive-destructive interference problem, involving the "forbidden" transition moments similar to the one that arises in the theory of Craig and Small on totally symmetric vibrational perturbations. The interferences can lead to a breakdown in mirror symmetry between the absorption and fluorescence spectra. The theory presented for a 2 vibrational model enables the relative signs of the 2 forbidden moments to be detd. by comparison of the relative intensities of 2 vibronic bands in absorption and fluorescence. In the case of naphthalene the forbidden moments assocd. with 509 and 938 cm-b3g modes are antiparallel. Calcns. for phenanthrene suggest that, although the Duschinsky effect should be included in any attempt at accurate vibronic intensity calcns., the constructive-destructive interference effects described by Craig and Small are primarily responsible for the gross deviations from mirror symmetry exptl. obsd. Illustrative calcns. show that the Duschinsky effect should not be neglected in the Herzberg-Teller theory of both fluorescence and absorption vibronic intensities.
- 15Kundu, S.; Roy, P. P.; Fleming, G. R.; Makri, N. Franck–Condon and Herzberg–Teller Signatures in Molecular Absorption and Emission Spectra. J. Phys. Chem. B 2022, 126 (15), 2899– 2911, DOI: 10.1021/acs.jpcb.2c00846There is no corresponding record for this reference.
- 16Kim, W.; Musser, A. J. Tracking Ultrafast Reactions in Organic Materials Through Vibrational Coherence: Vibronic Coupling Mechanisms in Singlet Fission. Adv. Phys. X. 2021, 6 (1), 1918022, DOI: 10.1080/23746149.2021.1918022There is no corresponding record for this reference.
- 17De Sio, A.; Sommer, E.; Nguyen, X. T.; Gross, L.; Popovic, D.; Nebgen, B. T.; Fernandez-Alberti, S.; Pittalis, S.; Rozzi, C. A.; Molinari, E. Intermolecular Conical Intersections in Molecular Aggregates. Nat. Nanotechnol 2021, 16 (1), 63– 68, DOI: 10.1038/s41565-020-00791-2There is no corresponding record for this reference.
- 18Singh, S.; Jones, W. J.; Siebrand, W.; Stoicheff, B. P.; Schneider, W. G. Laser Generation of Excitons and Fluorescencence in Anthracene Crystals. J. Chem. Phys. 1965, 42 (1), 330– 342, DOI: 10.1063/1.1695695There is no corresponding record for this reference.
- 19Smith, M. B.; Michl, J. Singlet Fission. Chem. Rev. 2010, 110 (11), 6891– 6936, DOI: 10.1021/cr100261319https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlKntbbF&md5=4632198f6c4b979ef92822fd6a3be047Singlet FissionSmith, Millicent B.; Michl, JosefChemical Reviews (Washington, DC, United States) (2010), 110 (11), 6891-6936CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. A theory of singlet fission is discussed along with its relation to photovoltaics. The literature is reviewed dealing with singlet fission in org. chromophores from the time of initial discovery of singlet fission to the present day.
- 20Smith, M. B.; Michl, J. Recent Advances in Singlet Fission. Annu. Rev. Phys. Chem. 2013, 64, 361– 386, DOI: 10.1146/annurev-physchem-040412-11013020https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntVCrsrY%253D&md5=763960f83db3bb2586b496278a8f1506Recent advances in singlet fissionSmith, Millicent B.; Michl, JosefAnnual Review of Physical Chemistry (2013), 64 (), 361-386CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews Inc.)A review. A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited mol. shares its energy with a ground-state neighbor to produce two triplet excited mols. It has been obsd. to occur in single-crystal, polycryst., and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivs., and it is argued that a wider structural variety would be desirable. The current state of the development of mol. structure design rules, based on first-principles theor. considerations, is described along with initial examples of implementation.
- 21Monahan, N.; Zhu, X. Y. Charge Transfer-Mediated Singlet Fission. Annu. Rev. Phys. Chem. 2015, 66, 601– 618, DOI: 10.1146/annurev-physchem-040214-12123521https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXnvFart7Y%253D&md5=4d571e4127b62c7dfc19275861b0cdcbCharge transfer-mediated singlet fissionMonahan, N.; Zhu, X.-Y.Annual Review of Physical Chemistry (2015), 66 (), 601-618CODEN: ARPLAP; ISSN:0066-426X. (Annual Reviews)Singlet fission, the splitting of a singlet exciton into two triplet excitons in mol. materials, is interesting not only as a model many-electron problem, but also as a process with potential applications in solar energy conversion. Here we discuss limitations of the conventional four-electron and mol. dimer model in describing singlet fission in cryst. org. semiconductors, such as pentacene and tetracene. We emphasize the need to consider electronic delocalization, which is responsible for the decisive role played by the Mott-Wannier exciton, also called the charge transfer (CT) exciton, in mediating singlet fission. At the strong electronic coupling limit, the initial excitation creates a quantum superposition of singlet, CT, and triplet-pair states, and we present exptl. evidence for this interpretation. We also discuss the most recent attempts at translating this mechanistic understanding into design principles for CT state-mediated intramol. singlet fission in oligomers and polymers.
- 22Walker, B. J.; Musser, A. J.; Beljonne, D.; Friend, R. H. Singlet Exciton Fission in Solution. Nat. Chem. 2013, 5 (12), 1019– 1024, DOI: 10.1038/nchem.180122https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhslygtbnL&md5=99dc6ccf7cd3d1cfbe0ca35149633490Singlet exciton fission in solutionWalker, Brian J.; Musser, Andrew J.; Beljonne, David; Friend, Richard H.Nature Chemistry (2013), 5 (12), 1019-1024CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermol. coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solns. of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene mol. The intermediate breaks up when the two triplets sep. to each TIPS-pentacene mol. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight.
- 23Wilson, M. W.; Rao, A.; Ehrler, B.; Friend, R. H. Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics Toward Devices. Acc. Chem. Res. 2013, 46 (6), 1330– 1338, DOI: 10.1021/ar300345h23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntFWnsL8%253D&md5=c4b74ef2c17945aeb7c70edbb4630f28Singlet Exciton Fission in Polycrystalline Pentacene: From Photophysics toward DevicesWilson, Mark W. B.; Rao, Akshay; Ehrler, Bruno; Friend, Richard H.Accounts of Chemical Research (2013), 46 (6), 1330-1338CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)A review. Singlet exciton fission is the process in conjugated org. mols. by which a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers 1st reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These studies used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest was recently re-kindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating addnl. photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chem., and small-mol. device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycryst. thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, the authors review the results of recent transient absorption and device-based studies of polycryst. pentacene. The authors address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, demonstration that triplet excitons generated via singlet fission in pentacene can be dissocd. at an interface with a suitable electron acceptor, such as fullerenes and IR-absorbing inorg. semiconducting quantum dots are discussed. The authors highlight recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous Si photovoltaic device. Although substantive challenges remain, both to better understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an IR-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could 1 day surpass the Shockley-Queisser limit.
- 24Musser, A. J.; Liebel, M.; Schnedermann, C.; Wende, T.; Kehoe, T. B.; Rao, A.; Kukura, P. Evidence for Conical Intersection Dynamics Mediating Ultrafast Singlet Exciton Fission. Nat. Phys. 2015, 11 (4), 352– 357, DOI: 10.1038/nphys324124https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXksVCmtbc%253D&md5=ba4f5c4e76401feaa359eb1dc2dee453Evidence for conical intersection dynamics mediating ultrafast singlet exciton fissionMusser, Andrew J.; Liebel, Matz; Schnedermann, Christoph; Wende, Torsten; Kehoe, Tom B.; Rao, Akshay; Kukura, PhilippNature Physics (2015), 11 (4), 352-357CODEN: NPAHAX; ISSN:1745-2473. (Nature Publishing Group)Singlet exciton fission is the process in org. semiconductors through which a spin-singlet exciton converts into a pair of spin-triplet excitons residing on different chromophores, entangled in an overall spin-zero state. For some systems, singlet fission has been shown to occur on the 100 fs timescale and with a 200% quantum yield, but the mechanism of this process remains uncertain. Here we study a model singlet fission system, TIPS-pentacene, using ultrafast vibronic spectroscopy. We observe that vibrational coherence in the initially photogenerated singlet state is transferred to the triplet state and show that this behavior is effectively identical to ultrafast internal conversion for polyenes in soln. This similarity in vibronic dynamics suggests that both multi-mol. singlet fission and single-mol. internal conversion are mediated by the same underlying relaxation processes, based on strong coupling between nuclear and electronic degrees of freedom. In its most efficient form this leads to a conical intersection between the coupled electronic states.
- 25Chan, W.-L.; Ligges, M.; Jailaubekov, A.; Kaake, L.; Miaja-Avila, L.; Zhu, X.-Y. Observing the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron Transfer. Science 2011, 334 (6062), 1541– 1545, DOI: 10.1126/science.121398625https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs1aju7vP&md5=641eb0459d5cc473874c67e162d41a6bObserving the Multiexciton State in Singlet Fission and Ensuing Ultrafast Multielectron TransferChan, Wai-Lun; Ligges, Manuel; Jailaubekov, Askat; Kaake, Loren; Miaja-Avila, Luis; Zhu, X.-Y.Science (Washington, DC, United States) (2011), 334 (6062), 1541-1545CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Two for One Conventional solar cells create a charge carrier each time a photon of light at or above a certain energy threshold is absorbed. Any energy embedded in short-wavelength photons that exceeds the threshold is largely wasted. Semonin et al. (p. ) now demonstrate a nanoparticulate lead selenide solar cell that channels a fraction of the excess energy into current. Chan et al. (p. ) explored the fundamental dynamics of multiple carrier generation in an org. (rather than inorg.) absorber and characterized a short-lived state that bridges the high-energy single carrier state and two discrete lower-energy carrier states. Multiple exciton generation (MEG) refers to the creation of two or more electron-hole pairs from the absorption of one photon. Although MEG holds great promise, it proved challenging to implement, and questions remain about the underlying photo-phys. dynamics in nanocryst. as well as mol. media. Using the model system of pentacene/fullerene bilayers and femtosecond nonlinear spectroscopies, the authors directly obsd. the multiexciton (ME) state ensuing from singlet fission (a mol. manifestation of MEG) in pentacene. Probably the state exists in coherent superposition with the singlet populated by optical excitation. Also multiple electron transfer from the ME state to the fullerene occurs on a subpicosecond time scale, which is one order of magnitude faster than that from the triplet exciton state.
- 26Duan, H.-G.; Jha, A.; Li, X.; Tiwari, V.; Ye, H.; Nayak, P. K.; Zhu, X.-L.; Li, Z.; Martinez, T. J.; Thorwart, M. Intermolecular Vibrations Mediate Ultrafast Singlet Fission. Sci. Adv. 2020, 6 (38), eabb0052 DOI: 10.1126/sciadv.abb0052There is no corresponding record for this reference.
- 27Seiler, H.; Krynski, M.; Zahn, D.; Hammer, S.; Windsor, Y. W.; Vasileiadis, T.; Pflaum, J.; Ernstorfer, R.; Rossi, M.; Schwoerer, H. Nuclear Dynamics of Singlet Exciton Fission in Pentacene Single Crystals. Sci. Adv. 2021, 7 (26), eabg0869 DOI: 10.1126/sciadv.abg0869There is no corresponding record for this reference.
- 28Neef, A.; Beaulieu, S.; Hammer, S.; Dong, S.; Maklar, J.; Pincelli, T.; Xian, R. P.; Wolf, M.; Rettig, L.; Pflaum, J. Orbital-Resolved Observation of Singlet Fission. Nature 2023, 616 (7956), 275– 279, DOI: 10.1038/s41586-023-05814-1There is no corresponding record for this reference.
- 29Kim, J.; Bain, D. C.; Ding, V.; Majumder, K.; Windemuller, D.; Feng, J.; Wu, J.; Patil, S.; Anthony, J.; Kim, W. Coherent photoexcitation of entangled triplet pair states. Nat. Chem. 2024, 16, 1680– 1686, DOI: 10.1038/s41557-024-01556-3There is no corresponding record for this reference.
- 30Breuer, T.; Celik, M. A.; Jakob, P.; Tonner, R.; Witte, G. Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor Crystals. J. Phys. Chem. C 2012, 116 (27), 14491– 14503, DOI: 10.1021/jp304080g30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XosFemu70%253D&md5=8ae3f27e4fbc339da7737775099adde5Vibrational Davydov Splittings and Collective Mode Polarizations in Oriented Organic Semiconductor CrystalsBreuer, Tobias; Celik, Mehmet A.; Jakob, Peter; Tonner, Ralf; Witte, GregorJournal of Physical Chemistry C (2012), 116 (27), 14491-14503CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Vibrational properties of highly ordered cryst. perfluoropentacene (PFP) films epitaxially grown on KCl(100) and NaF(100) substrates were studied by transmission IR spectroscopy and d. functional theory. The different mol. orientations adopted by PFP on both substrates (standing vs. lying) and their epitaxial ordering enable precise polarization-resolved measurements along individual crystallog. directions and thus allow an unambiguous exptl. detn. of the polarization of the IR modes. Computations of the vibrational spectra beyond the single-mol. approxn. were employed at the periodic dispersion-cor. d. functional level (PBE-D2PBC) and compared with nonperiodic calcns. (PBE-D2/def2-TZVPP). Thereby, a detailed mode assignment based on vibrational energies and polarization information was attained. A microscopic explanation for the exptl. obsd. Davydov splitting of some modes and the IR inactivity of others was derived based on the mutual coupling of the dynamical dipole moments of the 2 mols. within the unit cell. Exptl. obsd. modes not covered by theor. anal. were identified as combination bands of IR-active modes coupled to totally sym. modes of similar displacement patterns. These findings have important implications for future studies on structure and charge transport in org. semiconductors and the validation of theor. approaches for the modeling of vibrational spectra.
- 31Kolata, K.; Breuer, T.; Witte, G.; Chatterjee, S. Molecular Packing Determines Singlet Exciton Fission in Organic Semiconductors. ACS Nano 2014, 8 (7), 7377– 7383, DOI: 10.1021/nn502544d31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVaht7jI&md5=db8009c7b8ceddc719b227075c07cd19Molecular Packing Determines Singlet Exciton Fission in Organic SemiconductorsKolata, Kolja; Breuer, Tobias; Witte, Gregor; Chatterjee, SangamACS Nano (2014), 8 (7), 7377-7383CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Carrier multiplication by singlet exciton fission enhances photovoltaic conversion efficiencies in org. solids. This decay of 1 singlet exciton into 2 triplet states allows the extn. of ≤2 electrons per harvested photon and promises to overcome the Shockley-Queisser limit. The microscopic mechanism of singlet exciton fission, esp. the relation between mol. packing and electronic response, remains unclear, which therefore hampers the systematic improvement of org. photovoltaic devices. For the model system perfluoropentacene, exptl. singlet exciton fission is greatly enhanced for a slip-stacked mol. arrangement by addressing different crystal axes featuring different packing schemes. This reveals that the fission process strongly depends on the intermol. coupling: slip-stacking favors delocalization of excitations and allows for efficient exciton fission, while face-to-edge mol. orientations commonly found in the prevailing herringbone mol. stacking patterns even suppress it. The controversially debated role of excimer states as intermediary rather than competitive or precursory is clarified. The findings serve as a guideline for the design of next-generation mol. materials for application in future org. light-harvesting devices exploiting singlet exciton fission.
- 32Fujii, K.; Himcinschi, C.; Toader, M.; Kera, S.; Zahn, D.; Ueno, N. Vibrational Properties of Perfluoropentacene Thin Film. J. Electron Spectrosc. Relat. Phenom. 2009, 174 (1–3), 65– 69, DOI: 10.1016/j.elspec.2009.01.002There is no corresponding record for this reference.
- 33Salzmann, I.; Moser, A.; Oehzelt, M.; Breuer, T.; Feng, X. L.; Juang, Z. Y.; Nabok, D.; Della Valle, R. G.; Duhm, S.; Heimel, G. Epitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated Quartz. ACS Nano 2012, 6 (12), 10874– 10883, DOI: 10.1021/nn304260733https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xhs1Ons7%252FO&md5=6ebffad7140d6f872e989c6e7bfd1f0bEpitaxial Growth of π-Stacked Perfluoropentacene on Graphene-Coated QuartzSalzmann, Ingo; Moser, Armin; Oehzelt, Martin; Breuer, Tobias; Feng, Xinliang; Juang, Zhen-Yu; Nabok, Dmitrii; Della Valle, Raffaele G.; Duhm, Steffen; Heimel, Georg; Brillante, Aldo; Venuti, Elisabetta; Bilotti, Ivano; Christodoulou, Christos; Frisch, Johannes; Puschnig, Peter; Draxl, Claudia; Witte, Gregor; Muellen, Klaus; Koch, NorbertACS Nano (2012), 6 (12), 10874-10883CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Chem.-vapor-deposited large-area graphene is employed as the coating of transparent substrates for the growth of the prototypical org. n-type semiconductor perfluoropentacene (PFP). The graphene coating is found to cause face-on growth of PFP in a yet unknown substrate-mediated polymorph, which is solved by combining grazing-incidence X-ray diffraction with theor. structure modeling. In contrast to the otherwise common herringbone arrangement of PFP in single crystals and "standing" films, the authors report a π-stacked arrangement of coplanar mols. in "flat-lying" films, which exhibit an exceedingly low π-stacking distance of only 3.07 Å, giving rise to significant electronic band dispersion along the π-stacking direction, as evidenced by UPS. The study underlines the high potential of graphene for use as a transparent electrode in (opto-)electronic applications, where optimized vertical transport through flat-lying conjugated org. mols. is desired.
- 34Zeiser, C.; Moretti, L.; Geiger, T.; Kalix, L.; Valencia, A. M.; Maiuri, M.; Cocchi, C.; Bettinger, H. F.; Cerullo, G.; Broch, K. Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in Pentacene. J. Phys. Chem. Lett. 2021, 12 (31), 7453– 7458, DOI: 10.1021/acs.jpclett.1c0180534https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXhs1OlsLfJ&md5=f7b100501a52a512cde993994253db60Permanent Dipole Moments Enhance Electronic Coupling and Singlet Fission in PentaceneZeiser, Clemens; Moretti, Luca; Geiger, Thomas; Kalix, Lukas; Valencia, Ana M.; Maiuri, Margherita; Cocchi, Caterina; Bettinger, Holger F.; Cerullo, Giulio; Broch, KatharinaJournal of Physical Chemistry Letters (2021), 12 (31), 7453-7458CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)Singlet fission (SF), the photophys. process in which 1 singlet exciton is transformed into 2 triplets, depends inter alia on the coupling of electronic states. Here, the authors use fluorination and the resulting changes in partial charge distribution across the chromophore backbone as a particularly powerful tool to control this parameter in pentacene. The introduction of a permanent dipole moment leads to an enhanced coupling of Frenkel exciton and charge transfer states and to an increased SF rate which the authors probed using ultrafast transient absorption spectroscopy. These findings are contrasted with H-aggregate formation and a significantly reduced triplet-pair state lifetime in a fluorinated pentacene for which the different partial charge distribution leads to a negligible dipole moment.
- 35Sakamoto, Y.; Suzuki, T.; Kobayashi, M.; Gao, Y.; Fukai, Y.; Inoue, Y.; Sato, F.; Tokito, S. Perfluoropentacene: High-Performance P–N Junctions and Complementary Circuits with Pentacene. JACS. 2004, 126 (26), 8138– 8140, DOI: 10.1021/ja047625835https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXkvVSjtb4%253D&md5=7a1df958b075ea8c06255f123a8f5fddPerfluoropentacene: High-Performance p-n Junctions and Complementary Circuits with PentaceneSakamoto, Youichi; Suzuki, Toshiyasu; Kobayashi, Masafumi; Gao, Yuan; Fukai, Yasushi; Inoue, Youji; Sato, Fumio; Tokito, ShizuoJournal of the American Chemical Society (2004), 126 (26), 8138-8140CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report the synthesis and characterization of perfluoropentacene as an n-type semiconductor for org. field-effect transistors (OFETs). Perfluoropentacene is a planar and cryst. material that adopts a herringbone structure as obsd. for pentacene. OFETs with perfluoropentacene were constructed using top-contact geometry, and an electron mobility of 0.11 cm2 V-1 s-1 was obsd. Bipolar OFETs with perfluoropentacene and pentacene function at both neg. and pos. gate voltages. The improved p-n junctions are probably due to the similar d-spacings of both acenes. Complementary inverter circuits were fabricated, and the transfer characteristics exhibit a sharp inversion of the output signal with a high-voltage gain.
- 36Timmer, D.; Gittinger, M.; Quenzel, T.; Cadore, A. R.; Rosa, B. L. T.; Li, W. S.; Soavi, G.; Lünemann, D. C.; Stephan, S.; Silies, M. Ultrafast Coherent Exciton Couplings and Many-Body Interactions in Monolayer WS. Nano Lett. 2024, 24, 8117– 8125, DOI: 10.1021/acs.nanolett.4c01991There is no corresponding record for this reference.
- 37Timmer, D.; Lünemann, D. C.; Riese, S.; Sio, A. D.; Lienau, C. Full Visible Range Two-Dimensional Electronic Spectroscopy with High Time Resolution. Opt. Express 2024, 32 (1), 835– 847, DOI: 10.1364/OE.511906There is no corresponding record for this reference.
- 38Timmer, D.; Gittinger, M.; Quenzel, T.; Stephan, S.; Zhang, Y.; Schumacher, M. F.; Lützen, A.; Silies, M.; Tretiak, S.; Zhong, J.-H. Plasmon Mediated Coherent Population Oscillations in Molecular Aggregates. Nat. Commun. 2023, 14 (1), 8035, DOI: 10.1038/s41467-023-43578-4There is no corresponding record for this reference.
- 39Quenzel, T.; Timmer, D.; Gittinger, M.; Zablocki, J.; Zheng, F. L.; Schiek, M.; Lutzen, A.; Frauenheim, T.; Tretiak, S.; Silies, M. Plasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular Aggregates. ACS Nano 2022, 16 (3), 4693– 4704, DOI: 10.1021/acsnano.1c1139839https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38Xkt1Churc%253D&md5=96f3e1e23894b2d637fb580f697d5a8ePlasmon-Enhanced Exciton Delocalization in Squaraine-Type Molecular AggregatesQuenzel, Thomas; Timmer, Daniel; Gittinger, Moritz; Zablocki, Jennifer; Zheng, Fulu; Schiek, Manuela; Luetzen, Arne; Frauenheim, Thomas; Tretiak, Sergei; Silies, Martin; Zhong, Jin-Hui; De Sio, Antonietta; Lienau, ChristophACS Nano (2022), 16 (3), 4693-4704CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Enlarging exciton coherence lengths in mol. aggregates is crit. for enhancing the collective optical and transport properties of mol. thin film nanostructures or devices. We demonstrate that the exciton coherence length of squaraine aggregates can be increased from 10 to 24 mol. units at room temp. when prepg. the aggregated thin film on a metallic rather than a dielec. substrate. Two-dimensional electronic spectroscopy measurements reveal a much lower degree of inhomogeneous line broadening for aggregates on a gold film, pointing to a reduced disorder. The result is corroborated by simulations based on a Frenkel exciton model including exciton-plasmon coupling effects. The simulation shows that localized, energetically nearly resonant excitons on spatially well sepd. segments can be radiatively coupled via delocalized surface plasmon polariton modes at a planar mol.-gold interface. Such plasmon-enhanced delocalization of the exciton wave function is of high importance for improving the coherent transport properties of mol. aggregates on the nanoscale. Addnl., it may help tailor the collective optical response of org. materials for quantum optical applications.
- 40Timmer, D.; Zheng, F.; Gittinger, M.; Quenzel, T.; Lünemann, D. C.; Winte, K.; Zhang, Y.; Madjet, M. E.; Zablocki, J.; Lützen, A. Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes. JACS. 2022, 144 (41), 19150– 19162, DOI: 10.1021/jacs.2c08682There is no corresponding record for this reference.
- 41Breuer, T. Preparation and Characterization of Thin Films of Organic Semiconductors and their Heterostructures. Ph.D. Thesis, University of Marburg, Marburg, Germany, 2013.There is no corresponding record for this reference.
- 42Cocchi, C.; Breuer, T.; Witte, G.; Draxl, C. Polarized Absorbance and Davydov Splitting in Bulk and Thin-Film Pentacene Polymorphs. Phys. Chem. Chem. Phys. 2018, 20 (47), 29724– 29736, DOI: 10.1039/C8CP06384B42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitFyqs7zF&md5=efa3e8bbcf27be2c0e51a7f01ae72b80Polarized absorbance and Davydov splitting in bulk and thin-film pentacene polymorphsCocchi, Caterina; Breuer, Tobias; Witte, Gregor; Draxl, ClaudiaPhysical Chemistry Chemical Physics (2018), 20 (47), 29724-29736CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Pentacene is one of the most studied org. materials and in particular its optical properties have been the subject of intense research during the last two decades. In spite of such a widespread interest and of the extensive knowledge achieved so far, a no. of issues are still debated. One of the most relevant questions concerns the role of polymorphism and how it affects the lowest-energy exciton, which appears in the visible region and is subject to a sizable Davydov splitting. We address this problem in a combined theor. and exptl. work, where the optical absorption properties of three pentacene polymorphs are investigated within the whole energy range of visible light. Optical spectra computed from first principles in the framework of many-body perturbation theory are directly compared with the polarization-resolved absorbance, measured for three different pentacene phases (the two bulk polymorphs and the thin-film phase). In this way, we unambiguously identify the two Davydov components of the first exciton and the optical fingerprints of each considered phase. With very good agreement between theory and expt., we show that all polymorphs exhibit common features at the absorption onset, while phase-dependent characteristics appear only above 2 eV. We discuss the character of the lowest-lying singlet and triplet excitons, including dark ones, highlighting the contributions from the electronic bands and the role of the electron-hole interaction and of the local-field effects.
- 43Kumar, A. T. N.; Rosca, F.; Widom, A.; Champion, P. M. Investigations of Amplitude and Phase Excitation Profiles in Femtosecond Coherence Spectroscopy. J. Chem. Phys. 2001, 114 (2), 701– 724, DOI: 10.1063/1.132964043https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXmvFKr&md5=eb42607c979c7f4e908aa9811d92261fInvestigations of amplitude and phase excitation profiles in femtosecond coherence spectroscopyKumar, Anand T. N.; Rosca, Florin; Widom, Allan; Champion, Paul M.Journal of Chemical Physics (2001), 114 (2), 701-724CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)We present an effective linear response approach to pump-probe femtosecond coherence spectroscopy in the well-sepd. pulse limit. The treatment presented here is based on a displaced and squeezed state representation for the nonstationary states induced by an ultrashort pump laser pulse or a chem. reaction. The subsequent response of the system to a delayed probe pulse is modeled using closed form nonstationary linear response functions, valid for a multimode vibronically coupled system at arbitrary temp. When pump-probe signals are simulated using the linear response functions, with the mean nuclear positions and momenta obtained from a rigorous moment anal. of the pump induced (doorway) state, the signals are found to be in excellent agreement with the conventional third-order response approach. The key advantages offered by the moment anal.-based linear response approach include a clear phys. interpretation of the amplitude and phase of oscillatory pump-probe signals, a dramatic improvement in computation times, a direct connection between pump-probe signals and equil. absorption and dispersion lineshapes, and the ability to incorporate coherence assocd. with rapid nonradiative surface crossing. We demonstrate these aspects using numerical simulations, and also apply the present approach to the interpretation of exptl. amplitude and phase measurements on reactive and nonreactive samples of the heme protein myoglobin. The role played by inhomogeneous broadening in the obsd. amplitude and phase profiles is discussed in detail. We also investigate overtone signals in the context of reaction driven coherent motion.
- 44Nguyen, X. T.; Winte, K.; Timmer, D.; Rakita, Y.; Ceratti, D. R.; Aharon, S.; Ramzan, M. S.; Cocchi, C.; Lorke, M.; Jahnke, F. Phonon-Driven Intra-Exciton Rabi Oscillations in CsPbBr3 Halide Perovskites. Nat. Commun. 2023, 14 (1), 1047, DOI: 10.1038/s41467-023-36654-244https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXkt1OhsbY%253D&md5=170be8d47fd8df691bd7fcc8f5d19d42Phonon-driven intra-exciton Rabi oscillations in CsPbBr3 halide perovskitesNguyen, Xuan Trung; Winte, Katrin; Timmer, Daniel; Rakita, Yevgeny; Ceratti, Davide Raffaele; Aharon, Sigalit; Ramzan, Muhammad Sufyan; Cocchi, Caterina; Lorke, Michael; Jahnke, Frank; Cahen, David; Lienau, Christoph; De Sio, AntoniettaNature Communications (2023), 14 (1), 1047CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)Coupling electromagnetic radiation with matter, e.g., by resonant light fields in external optical cavities, is highly promising for tailoring the optoelectronic properties of functional materials on the nanoscale. Here, we demonstrate that even internal fields induced by coherent lattice motions can be used to control the transient excitonic optical response in CsPbBr3 halide perovskite crystals. Upon resonant photoexcitation, two-dimensional electronic spectroscopy reveals an excitonic peak structure oscillating persistently with a 100-fs period for up to ≈2 ps which does not match the frequency of any phonon modes of the crystals. Only at later times, beyond 2 ps, two low-frequency phonons of the lead-bromide lattice dominate the dynamics. We rationalize these findings by an unusual exciton-phonon coupling inducing off-resonant 100-fs Rabi oscillations between 1s and 2p excitons driven by the low-frequency phonons. As such, prevailing models for the electron-phonon coupling in halide perovskites are insufficient to explain these results. We propose the coupling of characteristic low-frequency phonon fields to intra-excitonic transitions in halide perovskites as the key to control the anharmonic response of these materials in order to establish new routes for enhancing their optoelectronic properties.
- 45Polli, D.; Antognazza, M. R.; Brida, D.; Lanzani, G.; Cerullo, G.; De Silvestri, S. Broadband Pump-Probe Spectroscopy with Sub-10-fs Resolution for Probing Ultrafast Internal Conversion and Coherent Phonons in Carotenoids. Chem. Phys. 2008, 350 (1–3), 45– 55, DOI: 10.1016/j.chemphys.2007.12.021There is no corresponding record for this reference.
- 46Andrzejak, M.; Mazur, G.; Musser, A. J.; Petelenz, P.; Skóra, T. Properties of Coherent Vibrational Wavepackets Critically Depend on the Method of Their Generation. J. Phys. Chem. C 2024, 128 (24), 9837– 9846, DOI: 10.1021/acs.jpcc.4c01485There is no corresponding record for this reference.
- 47Albrecht, A. C. Theory of Raman Intensities. J. Chem. Phys. 1961, 34 (5), 1476– 1484, DOI: 10.1063/1.1701032There is no corresponding record for this reference.
- 48Ruhman, S.; Joly, A. G.; Nelson, K. A. Coherent Molecular Vibrational Motion Observed in the Time Domain Through Impulsive Stimulated Raman-Scattering. IEEE J. Quantum Electron. 1988, 24 (2), 460– 469, DOI: 10.1109/3.146There is no corresponding record for this reference.
- 49Banin, U.; Bartana, A.; Ruhman, S.; Kosloff, R. Impulsive Excitation of Coherent Vibrational Motion Ground Surface Dynamics Induced by Intense Short Pulses. J. Chem. Phys. 1994, 101 (10), 8461– 8481, DOI: 10.1063/1.46810849https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXjt1yis7g%253D&md5=b7e1321e28594dfc02e3760f790240a3Impulsive excitation of coherent vibrational motion ground surface dynamics induced by intense short pulsesBanin, Uri; Bartana, Allon; Ruhman, Sanford; Kosloff, RonnieJournal of Chemical Physics (1994), 101 (10), 8461-81CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)A framework for understanding impulsively photoinduced vibrational coherent motion on the ground electronic surface is presented. In particular strong resonant excitation to a directly dissociative electronic surface is considered. Three distinct approaches are employed. A two surface Fourier wavepacket method explicitly including the field explores this process in isolated mols. A coordinate dependent two-level system is employed to develop a novel anal. approx. to the photoinduced quantum dynamics. The negligible computational requirements make it a powerful interactive tool for reconstructing the impulsive photoexcitation stage. Its anal. nature provides closed from expressions for the photoinduced changes in the material. Finally the full simulation of the process including the solvent effects is carried out by a numerical propagation of the d. operator. In all three techniques the excitation field is treated to all orders, allowing an anal. of current expts. using strong fields, resulting in substantial photoconversion. The emerging picture is that the impulsive excitation carves a coherent dynamic "hole" out of the ground surface d. A rigorous definition of the dynamic "hole" is constructed and used to define a measure of its coherence. In particular all photoinduced time dependence in the system can be directly related to the dynamic "hole". All three techniques are used to simulate the pump probe expt. on the sym. stretch mode of I3-3, including electronic and vibrational dephasing.
- 50Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119, 9506, DOI: 10.1021/acs.jpca.5b0594850https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlSmt7rJ&md5=0099060f0280493b160d6570da65c8dePrinciples and Applications of Broadband Impulsive Vibrational SpectroscopyLiebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
- 51Rather, S. R.; Fu, B.; Kudisch, B.; Scholes, G. D. Interplay of Vibrational Wavepackets during an Ultrafast Electron Transfer Reaction. Nat. Chem. 2021, 13 (1), 70– 76, DOI: 10.1038/s41557-020-00607-9There is no corresponding record for this reference.
- 52Liebel, M.; Schnedermann, C.; Kukura, P. Vibrationally Coherent Crossing and Coupling of Electronic States during Internal Conversion in β-Carotene. Phys. Rev. Lett. 2014, 112 (19), 198302, DOI: 10.1103/PhysRevLett.112.19830252https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Omsr7O&md5=2503b25a9cbbd8f5f8478ee18be59759Vibrationally coherent crossing and coupling of electronic states during internal conversion in β-caroteneLiebel, M.; Schnedermann, C.; Kukura, P.Physical Review Letters (2014), 112 (19), 198302/1-198302/5, 5 pp.CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Coupling of nuclear and electronic degrees of freedom mediates energy flow in mols. after optical excitation. The assocd. coherent dynamics in polyat. systems, however, remain exptl. unexplored. Here, we combined transient absorption spectroscopy with electronic population control to reveal nuclear wave packet dynamics during the S2 → S1 internal conversion in β-carotene. We show that passage through a conical intersection is vibrationally coherent and thereby provides direct feedback on the role of different vibrational coordinates in the breakdown of the Born-Oppenheimer approxn.
- 53Falke, S. M.; Rozzi, C. A.; Brida, D.; Maiuri, M.; Amato, M.; Sommer, E.; De Sio, A.; Rubio, A.; Cerullo, G.; Molinari, E. Coherent Ultrafast Charge Transfer in an Organic Photovoltaic Blend. Science 2014, 344 (6187), 1001– 1005, DOI: 10.1126/science.124977153https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXosFSmur0%253D&md5=07e4c1b7dbaf8e4bf8d63a4d190a98e7Coherent ultrafast charge transfer in an organic photovoltaic blendFalke, Sarah Maria; Rozzi, Carlo Andrea; Brida, Daniele; Maiuri, Margherita; Amato, Michele; Sommer, Ephraim; De Sio, Antonietta; Rubio, Angel; Cerullo, Giulio; Molinari, Elisa; Lienau, ChristophScience (Washington, DC, United States) (2014), 344 (6187), 1001-1005CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Blends of conjugated polymers and fullerene derivs. are prototype systems for org. photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, the authors elucidate the initial quantum dynamics of this process. Exptl., the authors obsd. coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with 1st-principle theor. simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-fs period matching that of the obsd. vibrational modes. The authors' results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound ref. system.
- 54Orlandi, G.; Siebrand, W. Theory of Vibronic Intensity Borrowing - Comparison of Herzberg-Teller and Born-Oppenheimer Coupling. J. Chem. Phys. 1973, 58 (10), 4513– 4523, DOI: 10.1063/1.1679014There is no corresponding record for this reference.
- 55Avila Ferrer, F. J.; Barone, V.; Cappelli, C.; Santoro, F. Duschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of Pyrene. J. Chem. Theory. Comput. 2013, 9 (8), 3597– 3611, DOI: 10.1021/ct400197y55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXpsFGmtb0%253D&md5=4f68741ea896d01b5efffe08c008b3aeDuschinsky, Herzberg-Teller, and Multiple Electronic Resonance Interferential Effects in Resonance Raman Spectra and Excitation Profiles. The Case of PyreneAvila Ferrer, Francisco J.; Barone, Vincenzo; Cappelli, Chiara; Santoro, FabrizioJournal of Chemical Theory and Computation (2013), 9 (8), 3597-3611CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)A recently developed time-independent approach for the calcn. of vibrational resonance Raman (vRR) spectra is able to describe Duschinsky and Herzberg-Teller (HT) effects acting on a single resonant state, together with interferential contributions arising from multiple electronic resonances, allowing one to study in detail how their interplay dets. both the vRR spectra at selected wavelengths and the Raman excitation profiles. The authors apply this methodol. to the study of the spectra of pyrene in MeCN, an ideal system since it exhibits 3 close-lying electronic transitions that are bright but also subjected to HT effects. To single out the different contributions to vRR line shapes the authors adopted 2 different adiabatic models for resonant-state potential energy surfaces, namely, Adiabatic Shift (only accounting from equil. geometry displacements) and Adiabatic Hessian (AH, including also the Duschinsky effects), and Franck-Condon (FC) or HT approxns. for the transition dipole. On balance, FC+HT calcns. within the AH model provide the best agreement with expt. Also, the methodol. permits to individuate bands in the exptl. spectra due to the simultaneous contribution of >1 resonant state and to point out and analyze interferential effects between the FC and HT terms in each resonance Raman process, together with FC-HT and HT-HT interferences between different electronic states.
- 56Petelenz, P.; Andrzejak, M. Vibronic Interpretation of the Low-Energy Absorption Spectrum of the Sexithiophene Single Crystal. J. Chem. Phys. 2000, 113 (24), 11306– 11314, DOI: 10.1063/1.1290026There is no corresponding record for this reference.
- 57Witkowski, A.; Moffitt, W. Electronic Spectra of Dimers - Derivation of the Fundamental Vibronic Equations. J. Chem. Phys. 1960, 33 (3), 872– 875, DOI: 10.1063/1.1731278There is no corresponding record for this reference.
- 58Zgierski, M. Z.; Pawlikowski, M. Absorption and Circular-Dichroism Spectra of Dimeric Systems - Extended Dimer Model. J. Chem. Phys. 1983, 79 (4), 1616– 1633, DOI: 10.1063/1.446033There is no corresponding record for this reference.
- 59Bizimana, L. A.; Carbery, W. P.; Gellen, T. A.; Turner, D. B. Signatures of Herzberg-Teller Coupling in Three-Dimensional Electronic Spectroscopy. J. Chem. Phys. 2017, 146 (8), 084311, DOI: 10.1063/1.4976995There is no corresponding record for this reference.
- 60Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77 (18), 3865– 3868, DOI: 10.1103/PhysRevLett.77.386560https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XmsVCgsbs%253D&md5=55943538406ee74f93aabdf882cd4630Generalized gradient approximation made simplePerdew, John P.; Burke, Kieron; Ernzerhof, MatthiasPhysical Review Letters (1996), 77 (18), 3865-3868CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Generalized gradient approxns. (GGA's) for the exchange-correlation energy improve upon the local spin d. (LSD) description of atoms, mols., and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental consts. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential.
- 61Günder, D.; Valencia, A. M.; Guerrini, M.; Breuer, T.; Cocchi, C.; Witte, G. Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN: PFP Cocrystalline Films: Limits of Nonperiodic Modeling. J. Phys. Chem. Lett. 2021, 12 (40), 9899– 9905, DOI: 10.1021/acs.jpclett.1c02761There is no corresponding record for this reference.
- 62Valencia, A. M.; Bischof, D.; Anhäuser, S.; Zeplichal, M.; Terfort, A.; Witte, G.; Cocchi, C. Excitons in Organic Materials: Revisiting Old Concepts with New Insights. Electron. Struct. 2023, 5 (3), 033003, DOI: 10.1088/2516-1075/acf2d4There is no corresponding record for this reference.
- 63Liebel, M.; Schnedermann, C.; Wende, T.; Kukura, P. Principles and Applications of Broadband Impulsive Vibrational Spectroscopy. J. Phys. Chem. A 2015, 119 (36), 9506– 9517, DOI: 10.1021/acs.jpca.5b0594863https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlSmt7rJ&md5=0099060f0280493b160d6570da65c8dePrinciples and Applications of Broadband Impulsive Vibrational SpectroscopyLiebel, M.; Schnedermann, C.; Wende, T.; Kukura, P.Journal of Physical Chemistry A (2015), 119 (36), 9506-9517CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)An exptl. setup is presented for recording vibrational coherences and Raman spectra of mols. in their ground and excited electronic states at 50-3000 cm-1 using broadband impulsive vibrational spectroscopy. The approach relies on the combination of a <10 fs excitation pulse with an uncompressed white light continuum probe, which drastically reduces exptl. complexity compared to frequency domain based techniques. The parameters detg. vibrational coherence amplitudes, outline how to optimize the exptl. setup including approaches aimed at conclusively assigning vibrational coherences to specific electronic states, and provide a clear comparison with existing techniques are discussed. To demonstrate the applicability of the spectroscopic approach, several examples reveal the evolution of vibrational coherence in rhodopsin and β-carotene.
- 64Lanzani, G.; Cerullo, G.; De Silvestri, S. Coherent Vibrational Dynamics; CRC Press, 2007.There is no corresponding record for this reference.
- 65Grupp, A.; Budweg, A.; Fischer, M. P.; Allerbeck, J.; Soavi, G.; Leitenstorfer, A.; Brida, D. Broadly Tunable Ultrafast Pump-Probe System Operating at Multi-kHz Repetition Rate. J. Opt. 2018, 20 (1), 014005, DOI: 10.1088/2040-8986/aa9b07There is no corresponding record for this reference.
- 66Brida, D.; Manzoni, C.; Cerullo, G. Phase-Locked Pulses for Two-Dimensional Spectroscopy by a Birefringent Delay Line. Opt. Lett. 2012, 37 (15), 3027– 3029, DOI: 10.1364/OL.37.00302766https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC38flt1Sqsg%253D%253D&md5=774e1891ccbfb9f8581dab50436ee22ePhase-locked pulses for two-dimensional spectroscopy by a birefringent delay lineBrida Daniele; Manzoni Cristian; Cerullo GiulioOptics letters (2012), 37 (15), 3027-9 ISSN:.We introduce the translating wedge-based identical pulses encoding system, a novel device for the generation of collinear, interferometrically locked ultrashort pulse pairs. By means of birefringent wedges, we are able to control the pulse delay with attosecond precision and stability better that λ/360, without affecting the pulse duration and in a spectral range that spans from UV to mid-IR. This device is expected to dramatically simplify two-dimensional spectroscopy experiments.
- 67Frisch, M. e.; Trucks, G.; Schlegel, H. B.; Scuseria, G.; Robb, M.; Cheeseman, J.; Scalmani, G.; Barone, V.; Petersson, G.; Nakatsuji, H. Gaussian 16; Gaussian, Inc.: Wallingford, CT, 2016.There is no corresponding record for this reference.
- 68Lee, S. Y.; Heller, E. J. Time-Dependent Theory of Raman Scattering. J. Chem. Phys. 1979, 71 (12), 4777– 4788, DOI: 10.1063/1.43831668https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3cXms12ltA%253D%253D&md5=4233d1d72a3c69c20cb74a9e7c27ef2aTime-dependent theory of Raman scatteringLee, Soo-Y.; Heller, E. J.Journal of Chemical Physics (1979), 71 (12), 4777-88CODEN: JCPSA6; ISSN:0021-9606.A time-dependent picture of vibrational Raman scattering in the weak field limit is presented. From this viewpoint the static effects, due to the coordinate dependence of the electronic transition dipole, can be sepd. from the dynamic effects that arise from wave packet propagation on the Born-Oppenheimer surfaces. Away from resonance, the energy uncertainty relation gives the propagation time necessary to obtain the cross section as being inversely proportional to the mismatch of the excitation frequency with the excited surface. The wave packet, given by the initial vibrational wave function times the transition dipole, hardly moves on the excited surface when the excitation frequency is far from resonance. As the excitation frequency is tuned closer to resonance, the propagated wave packet samples a larger portion of the surface. By using the short time approxn. to the propagator, formulas were obtained for the cross section that are applicable for Raman scattering by polyatomics. The short time approxn. is expected to be good away from resonance independent of the nature of the surface, and also on resonance with a repulsive surface. For an attractive surface, the approxn. gives the av. resonant cross section useful in the case when the vibrational structures cannot be obsd.
- 69Porezag, D.; Pederson, M. R. Infrared Intensities and Raman-Scattering Activities Within Density-Functional Theory. Phys. Rev. B 1996, 54 (11), 7830, DOI: 10.1103/PhysRevB.54.783069https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XmtVWrtb0%253D&md5=284a618dbda84734a287f7affa0eea2bInfrared intensities and Raman-scattering activities within density-functional theoryPorezag, Dirk; Pederson, Mark R.Physical Review B: Condensed Matter (1996), 54 (11), 7830-7836CODEN: PRBMDO; ISSN:0163-1829. (American Physical Society)The computational complexity assocd. with the d.-functional-based detn. of IR intensities and nonresonant Raman scattering activities is the same as that required for vibrational modes. Further, the authors use extremely large basis sets to det. the intrinsic accuracy for calcg. such phenomena within the d.-functional theory. The authors present benchmark calcns. on CH4, H2O, C2H2, C2H4, and C2H6 within both the local-d. approxn. (LDA) and the generalized gradient approxn. (GGA). Tests of the reliability and numerical stability of the theor. scheme are presented. To obtain reliable results, appropriate polarization basis functions and well-converged wave functions are necessary. While most of the Raman spectra predicted by LDA agree very well with exptl. data, some of the IR intensities show substantial errors. The GGA functional overcomes most of these deficiencies, leading to an overall good agreement with expt.
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X-ray diffraction of PFP films on KCl and NaF; polarization-resolved UV/vis absorption spectra of single crystalline PFP islands on KCl and NaF; pulse characterization; fluence study; data analysis (PDF)
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