Ligand-Directed Self-Assembly of Organic-Semiconductor/Quantum-Dot Blend Films Enables Efficient Triplet Exciton-Photon Conversion

Blends comprising organic semiconductors and inorganic quantum dots (QDs) are relevant for many optoelectronic applications and devices. However, the individual components in organic-QD blends have a strong tendency to aggregate and phase-separate during film processing, compromising both their structural and electronic properties. Here, we demonstrate a QD surface engineering approach using electronically active, highly soluble semiconductor ligands that are matched to the organic semiconductor host material to achieve well-dispersed inorganic–organic blend films, as characterized by X-ray and neutron scattering, and electron microscopies. This approach preserves the electronic properties of the organic and QD phases and also creates an optimized interface between them. We exemplify this in two emerging applications, singlet-fission-based photon multiplication (SF-PM) and triplet–triplet annihilation-based photon upconversion (TTA-UC). Steady-state and time-resolved optical spectroscopy shows that triplet excitons can be transferred with near unity efficiently across the organic–inorganic interface, while the organic films maintain efficient SF (190% yield) in the organic phase. By changing the relative energy between organic and inorganic components, yellow upconverted emission is observed upon 790 nm NIR excitation. Overall, we provide a highly versatile approach to overcome longstanding challenges in the blending of organic semiconductors with QDs that have relevance for many optical and optoelectronic applications.


Small-Angle Neutron Scattering
SANS was carried out on the SANS2D 1 small-angle diffractometer at the ISIS Pulsed Neutron Source (STFC Rutherford Appleton Laboratory, Didcot, U.K.). 2 Samples before (PbS-OA) and after ligand exchange (PbS-TET-CA) were prepared in deuterated toluene, providing the necessary contrast, and were contained in 2 mm path length quartz cells (Hellma GmbH).In the following, the magnitude of the scattering vector is defined as  = !"#$%& ' where 2 is the angle between the incident and scattered X-ray or neutron of wavelength.A simultaneous q-range of 0.006 -1.2 Å -1 was achieved utilizing an incident wavelength range of 1.65 -16.5 Å and employing an instrument set up of L1 = L2 = 4 m, where L1 and L2 are the pre and post sample flightpaths respectively, with the rear detector offset vertically 75 mm and horizontally 100 mm.The beam diameter was collimated to 12 mm at the sample.For all collected data, each raw scattering data set was corrected for the detector efficiencies, sample transmission and background scattering and converted to scattering cross-section data (∂Σ/∂Ω vs. q) using the instrument-specific software. 3These data were placed on an absolute scale (cm -1 ) using the scattering from a standard sample (a solid blend of hydrogenous and perdeuterated polystyrene) in accordance with established procedures. 4ropriate backgrounds were subtracted from each sample, namely oleic acid in d-toluene for PbS-OA 5 and TIPS-tetracene in d-toluene for PbS-TET-CA, to approximate the scattering from residual TET-CA in solution following ligand exchange.Fitting was performed using the SasView software package. 6The data were fitted to a core-shell sphere model with a hard-sphere structure factor.The core-shell sphere model takes into account the scattering from the spherical core and a single spherical shell, so that the scattering intensity (when multiplying by the appropriate structure factor) is given by where and  ( and  # are the volumes,  ( and  # are the radii, and  ( and  # are the scattering length densities of the core and shell respectively, and  #8*9 is the scattering length density of the solvent.() is, as stated, the hard sphere structure factor (as implemented in SasView version 4.2.2) which is a calculation of the interparticle structure factor for monodisperse spherical particles interacting through excluded volume interactions.This is calculated using the Percus-Yevick closure 7 where the inter-particle potential is given as: The core radius of 16.3 Å and lognormal polydispersity of 0.1 were used as constraints to the SANS fitting, detailed procedures for the characterisation of this PbS-OA sample set is described elsewhere. 5The main output of the model was therefore a scattering length density, thickness, and polydispersity of the ligand shell.In all cases, the component scattering length densities are taken as  :; = -0.24(packed OA tails),  <=<5>; = 0.9 and  ?5@8*A+%+ = 5.68 ´ 10 -6 Å -2 .In the case of PbS-OA, the shell SLD is simply given by  #B+** =  :;  :; +  #8*9+%@  #8*9+%@ allowing simple calculation of the respective volume fractions within the shell of oleic acid and solvent as  :; = 0.83 and  #8*9+%@ = 0.17.In the case of PbS-TET-CA, a ligand density on the order of 0.6 ± 0.1 ligands/nm 2 is typically measured by absorption.The exchanged ligand shell is therefore described by  #B+** =  <=<5>;  <=<5>; +  :;  :; +  #8*9+%@  #8*9+%@ .For a TET-CA ligand density of 0.6 ± 0.1 ligands/nm 2 , this is consistent with values of  <=<5>; = 0.35,  :; = 0.42 and  #8*9+%@ = 0.23, leading to the conclusion that significant TET-CA functionalisation of the PbS has been achieved, but that residual OA is also present.

Grazing Incidence X-ray Scattering
Grazing incidence X-ray scattering measurements were carried out on two instruments Xeuss 2.0 instrument equipped with an Excillum MetalJet liquid gallium X-ray source for TIPS-Tc:PbS-TET-Ca and Rubrene:PbS-TET-CA films and at I07 (Diamond Light Source, Rutherford, U.K.) for F-TA-PbS-TACA films.
The Xeuss 2.0 instrument equipped with an Excillum MetalJet liquid gallium X-ray source.Alignment was performed on silicon substrates via three iterative height (z) and rocking curve (Ω) scans, with the final grazing incidence angle set to Ω = 0.2° and collimating slits of 0.25 ´ 0.3 mm ("high resolution" mode) were employed.Scattering patterns for TIPS-Tc:PbS-TET-CA films were recorded on a vertically-offset Pilatus 1M detector with a sample to detector distance of 559 mm, calibrated using a silver behenate standard to achieve a q-range of 0.045 -1.2 Å -1 .Scattering patterns for rubrene:PbS-TET-CA films were recorded on a vertically offset Pilatus 1 M detector with a sample-to-detector distance of 332 mm, calibrated using a silver behenate standard to achieve a q-range of 0.045-1.5Å -1 .Two-dimensional images were recorded with exposure times of 900 and 600 s for the reseective TIPS-Tc:PbS-TET-CA and rubrene:PbS-TET-CA films.Data reduction was performed using GISAXS-GUI MATLAB toolbox. 8Two-dimensional scattering data was reduced to one-dimensional via radial integration, which was performed with a mask to remove contributions from "hot pixels", substrate horizon and the reflected beam.Fitting was performed using the SasView software package. 6 F-TA-PbS-TA-CA films were prepared on silicon and GIWAXS was performed at I07 (Diamond Light Source, Rutherford, U.K.) at an X-ray beam energy of 12.4 keV.Scattering patterns were recorded on a vertically-offset Pilatus 2M detector with a sample to detector distance of 635.62 mm, calibrated using a silver behenate standard to achieve a Q range of 0.045 -1.8 Å -1 .For scattering data collected using either instrument, alignment was performed via three iterative height (z) and rocking curve (Ω) scans, with the final grazing incidence angle set to Ω = 0.3º.The two-dimensional scattering patterns were masked to remove the sample horizon, detector module gaps and beam-stop and radially integrated from the apparent beam centre.Data correction and reduction was performed using the GIXSGUI MATLAB toolbox. 1 Twodimensional scattering data was reduced to one-dimensional via radial integration, which was performed with a mask to remove contributions from "hot pixels", the substrate horizon and reflected beam.
where scale is the volume fraction of spheres,  C is the volume of the primary particle,  *)@@$(+ is a volume correction for the crystal structure, () is the form factor of the sphere (normalized), and () is the paracrystalline structure factor for a face-centered cubic structure.
The lattice correction (the occupied volume of the lattice) for a face-centred cubic structure of particles of radius  and the nearest neighbour separation  is The distortion factor (one standard deviation) of the paracrystal is included in the calculation of () where g is a fractional distortion based on the nearest neighbour distance.Rubrene:PbS-TET-CA solutions were prepared at 10:2.5 mg mL -1 , respectively, in toluene were heated to 50 °C for 1 h and vortex-mixed prior to use.Silicon substrates were cleaned with Decon and ethanol followed by three deionized water rinses.Fifty microliters of casting solutions was deposited on silicon substrates and spun-cast at 1500 rpm for 2 min.The two dimensional grazing incidence X-ray scattering data for PbS-TET-CA:Rubrene films is shown in Supplementary Figure 1.Scattering data for F-TA:PbS-TA-CA blend is shown in Supplementary Figure 2.This data could not be fitted to a single FCC paracrystal model as for the TIPS-Tc:QD blends.A model was fitted to the data comprising a spherical form factor with a hard-sphere structure factor that describes scattering from QDs still distributed with liquid-like order within the film, in addition to a FCC paracrystal contribution to take into account regions of the film where the QDs are close-packed into a colloidal crystal.

Supplementary Figure 1. (a) Two dimensional grazing incidence X-ray scattering data for
The expression of () for this sphere×hard-sphere+FCC model is given as: where () is the form factor of the sphere (normalized) and () is the hard sphere structure factor that multiplies the form factor for dispersed scatterers at each point (and is equivalent in implementation in SAXS as it is in SANS; see Section 2.1 above for additional detail).The volume fraction of scattering material in either sphere*hard sphere or FCC colloidal crystal was obtained from a limited-range calculation (i.e.performed on only the experimental q-range without extrapolation) of the scattering invariant  *$L$@+?* = ∫  -()

Supplementary Figure 2. Two dimensional grazing incidence X-ray scattering data for
for each of the respective model components.

TEM
Transmission electron microscopy to investigate film morphology was performed using an FEI Tecnai F20 at 200 kV accelerating voltage.Film samples at 50 mg mL -1 QDs and 100 mg mL -1 TIPS-Tc were transferred onto 200-mesh Cu grids (Agar AGS160).

Ligand Exchange
Synthesis of PbS QDs was carried out following the procedure by Hines and Scholes with modifications 10,11 In summary, PbO (0.45 g), oleic acid (8 g) and 1-octadecene (10 g) were degassed in a three-necked flask at 110 °C for 2 h.The temperature was then reduced to 95 °C.Under nitrogen, a solution of bis(trimethylsilyl)sulphide (210 μL) in 1-octadecene (5 mL) was rapidly injected into the lead precursor solution.After cooling naturally to room temperature, the PbS QDs were washed 4 times by precipitation/redispersion with acetone and hexane.The purified QDs were stored in a nitrogen filled glovebox at high concentration (>40 mg mL -1 / >100 μM) until use.Ligand exchange was carried out under nitrogen.The QDs in toluene were diluted to 8 mg mL -1 in a Toluene/THF mixture of 4:1.The ligand in 100 mg mL -1 THF solution was added to the QD solution, keeping a ligand to QD mass ratio of 1:1 for TET-CA and 1:2 for TA-CA (for medium and high coverage 1:1 and 2:1ratios were used, respectively).
Ligand coverage was estimated from UV/Vis absorption using the molar absorption coefficient of the TET-CA ligand as 25500 M -1 cm -1 at the peak absorption in toluene.The ligand area was used assuming the QD as a sphere with a diameter estimated from the empiric formula in Moreels et al. 12 Supplementary Figure 3: Absorption of PbS-OA, PbS-TET-CA after ligand exchange and difference spectra used to calculate the ligand coverage.

Steady-State Absorption
A Shimadzu UV-3600Plus spectrometer was used to measure the absorbance spectra of the solutions and films.

PLQE and Excitation Scan of SF-PM films
The integrating sphere and PLQE measurement procedure has been described previously. 13,14In summary, an integrating sphere with a Spectralon-coated interior (Newport 819C-SL-5.3)was used.515 nm (2.9 x 10 15 photons s 5D cm 5-at the sample) and 658 nm (1.8 x 10 16 photons s 5D cm 5-at the sample) laser diodes (Thorlabs) with a beam diameter at the sample of 3 mm was used as the excitation source.Light from the sphere was coupled into an Andor Kymera 328i Spectrograph equipped with an InGaAs detector (Andor, iDus InGaAs 490).From the reproducibility of consecutive measurements, we estimate the absolute uncertainty on a PLQE value at 1 unit %.
Excitation scans were recorded on an Edinburgh Instruments FLS 980 Fluorimeter using an InGaAs detector for recording the IR emission (1300 ± 20 nm).

Transient Absorption
The short time (fs-ns) transient absorption setup has been described previously. 14In summary, a Light Conversion PHAROS laser system with 400 μJ per pulse at 1030 nm with a repetition rate of 38 kHz was used.The output is divided, one part is focused onto a 4 mm YAG substrate to produce the continuum The longtime (ns-μs) transient absorption setup has also been described previously. 14In short, the pumpprobe setup consists of a probe from a LEUKOS Disco 1 UV supercontinuum laser (STM-1-UV, 1 kHz) and a pump generated in a TOPAS optical amplifier, pumped with the output from a Spectra-Physics Solstice Ace Ti:Sapphire amplifier (1 kHz).The probe beam is split into a reference and probe and both are focused onto the sample.A pair of line image sensors (Hamamatsu, G11608) mounted on a spectrograph (Andor Solis, Shamrock SR-303i) is used to detect the signal, using a custom-built board from Stresing Entwickslungsburo to read out the signal.

IR TCSPC
Samples were excited with a pulsed supercontinuum laser (Fianum Whitelase SC-400-4, 6 ps pulse length) at 0.2 MHz repetition rate.The pump wavelength set to either 535 nm or 650 nm (full-width at half-maximum 10 nm) with dielectric filters (Thorlabs).Pump scatter from the laser excitation within the photoluminescence path to the detector was filtered-out with an absorptive 900 nm long-pass filter (Thorlabs).The infrared photoluminescence was focused and detected by a single-photon avalanche photodiode based on InGaAs/InP (MPD-InGaAs-SPAD).

Steady-State and Magnetic Dependent PL
Similar to previously described temperature and current-controlled laser diodes (Thorlabs) were used to generate stable 532 nm and 658 nm laser beams. 14The incident beam was attenuated as desired and focused onto the sample while PL from the sample was collected and focused into an Andor Kymera 328i Spectrometer and spectra recorded using either a Si-CCD (Andor iDus 420) for the visible region or an InGaAs detector (Andor, Dus InGaAs 490) for the NIR region.For magnetic field dependent PL measurements, an electromagnet was placed such that the sample was located within the poles of the electromagnet.As described previously, 15 the electromagnet was driven to achieve varying magnetic field strengths by using a Keithley 2400 variable voltage source connected to a current amplifier.The magnetic field between the poles (at the sample position) was calibrated to the applied voltage by a Gauss-meter.
When measuring the PL from the PbS QDs (near IR region), both an RG1000 (Schott) and PL950 (Thorlabs) long pass filters were placed in front of the entrance to the spectrometer.These removed laser scatter and higher order peaks from the grating.After averaging over multiple sweeps of the magnetic field and integration of the spectra, the percentage change relative to the spectrum under zero applied field strength was calculated.

Synthesis of Ligands and Organic Host
Solvents were purchased in bulk from VWR, other reagents were purchased from Sigma Aldrich and were used as received.NMR spectra were measured on a 400 MHz or 600 MHz Bruker instrument, chemical shifts are reported in ppm and referenced to the deuterated solvents used.MALDI TOF MS was analyzed on a Bruker Microflex LRF with no matrix.X-ray diffraction data were collected at 90.0(2) K on either a Nonius kappaCCD diffractometer using MoK(alpha) X-rays or a Bruker-Nonius X8 Proteum diffractometer with graded-multilayer focussed CuK(alpha) X-rays.For the MoK(alpha) data, corrections for absorption were applied using SADABS (Krause, L., Herbst-Irmer, R., Sheldrick, G.M. & Stalke, D. (2015).J. Appl.
Refinement was carried out against F^2 by weighted full-matrix least-squares (SHELXL).Hydrogen atoms were found in difference maps but subsequently placed at calculated positions and refined using riding models.Non-hydrogen atoms were refined with anisotropic displacement parameters.Atomic scattering factors were taken from the International Tables for Crystallography (International Tables for Crystallography, vol C: Mathematical, Physical and Chemical Tables.A.J.C. Wilson, Ed. (1992).Kluwer Academic Publishers, Holland.).
We initially attempted to prepare the carboxylic acid ligand following the same approach used to prepare TIPS Tetracene carboxylic acid 16 -beginning with an appropriately brominated quinone, a lithium acetylide is added to the carbonyl moieties to form an intermediate dialkoxide.This addition is immediately followed by in-situ metal/halogen exchange and carboxylation, and finally a deoxygenative workup (Scheme 1).This route seemed particularly appealing, because the requisite bromoquinone (Q-Br) was reported to be easily prepared. 17After following the procedure shown in Scheme 1 (top), the isolated product did not yield the expected NMR spectrum, so crystals were grown.X-ray analysis of these crystals did not yield a well-refined structure, but it did suggest the presence of substantial substitution of bromine on the 3-position of the thiophene, along with carboxylic acid on the 2-position.To determine whether this product arose from an unusual 'halogen dance reaction, 18 or whether the starting material had been mis-identified, we prepared the corresponding trimethylsilylethynyl derivative in good yield (Scheme 1, middle), which yielded excellent crystals.The well-resolved structure shows the bromine substituent strictly on the 3-position of the chromophore, suggesting that the structure of the product from the literature synthesis was incorrect (no crystallographic analysis was reported in that work).It is thus likely that structures from that, and other publications using the same method, 19 likely do not possess the assigned structures, since none have been confirmed crystallographically, and the difference in 1 H NMR spectra will be subtle.
We recently demonstrated that thienoacenes are very amenable to simple deprotonation and carboxylation using LDA.Starting from known triisopropylsilylethynyl substituted thienoanthracene, 20 were able to make the corresponding carboxylic acid in 52% isolated yield (see below).(prepared as described in reference 17) was added in one portion, and the mixture allowed to stir until all quinone had dissolved.Three hours after complete dissolution, the reaction mixture was quenched with 5 mL of 10% aqueous HCl, followed by 6 g (27 mmol) of stannous chloride dihydrate.This mixture was allowed to stir for 30 minutes, and was then poured into hexanes and extracted three times with water.The organic phase was then dried over magnesium sulfate, and poured directly through a thin (2 cm) silica gel plug (hexanes).After removal of solvent, the resulting solid was recrystallized from acetone to yield 1.2 g (80%) of the 3-bromo thienoanthracene, as confirmed by crystallographic analysis.

5,10-bis(triisopropylsilylethynyl) thienoanthracene-2-carboxylic acid (TA-CA):
To a flame-dried flask with stir bar that had been cooled under a constant flow of dry nitrogen, 5,10-bis(triisopropylsilylethynyl) thienoanthracene (prepared as described in reference 20, 1.19 g, 2 mmol) was dissolved in 5 mL anhydrous THF.The reaction mixture was cooled to -78 °C and 10 mL of 1M LDA (5 eq) were added dropwise, and the reaction mixture was stirred for approximately 45 minutes at that temperature.Solid CO2 was next added in great excess, and the reaction mixture was stirred for an additional 20 minutes.The reaction was quenched with 10% HCl and extracted with ethyl acetate.The organic layers were combined, dried with magnesium sulfate, and concentrated via rotary evaporation.The product was purified on silica with ethyl acetate and recrystallized with acetone to give small red crystals (0.66 g, 52%.In a flame dried 100 mL round bottom flask, 1.11 g of tri(isobutyl)silyl acetylene (5.05 mmol) was dissolved in 10 mL of n-heptane and cooled to 0 °C.1.96 mL of 2.5 M n-BuLi (4.89 mmol) was added dropwise to the reaction solution and stirred for 30 minutes.The reaction solution was diluted with 40 mL of n-heptane.0.36 g of 2-fluoro-5,10-thienoanthracene quinone (1.27 mmol) was added to the reaction solution, followed by 7 mL of dry THF.The reaction mixture was brought to room temperature and stirred for 16 hours.The reaction was quenched with water, extracted with DCM and the combined organic phases washed with water.The organic phase was dried over MgSO4, filtered, and the solvent evaporated in vacuo.The resulting yellow oil was run through a thick pad of silica using HPLC-grade hexane as eluent to remove excess acetylene, followed by dichloromethane to collect the intermediate product, ethynylated thienoantracene diol as a yellow oil which was immediately used in the next step.The ethynylated thienoanthracene diol was dissolved in 15 mL of THF and 15 mL of 10% HCl, 1.41 g of SnCl2•2H2O (5.64 mmol) was added to the reaction mixture along with 20 mL of THF and stirred for 1 hour.The solution was extracted with the HPLCgrade hexane and dried over MgSO4, the solvent evaporated in vacuo.The resulting orange solid was purified over a thick silica plug, using HPLC-grade hexane as eluent.After the removal of solvent, the final product, F-TA was collected as a yellow solid (0.38 g, 62%.

Upconversion in Solution
Following the De Mello method 23 The solution upconversion measurements were determined in an integrating sphere fiber-coupled to a spectrograph (Shamrock SR-303i, ANDOR) with CCD camera (Andor iDus DU420A Si CCD, ANDOR), calibrated for spectral sensitivity of the detector at each wavelength.The upconverted emission was corrected for reabsorption using a spectra obtained from a solution with low concentration of the annihilator.

Upconversion in Films
Absorption spectra were measured of the films using a spectrometer (UV3600-Plus, Shimadzu) equipped with an integrating sphere.Upconverted emission spectra was measured using a spectrograph (Shamrock SR-303i, ANDOR) with CCD camera (Andor iDus DU420A Si CCD, ANDOR), calibrated for spectral sensitivity of the detector at each wavelength.Two CW lasers of 790 nm and 405 nm (Thorlabs) were overlapped on the sample from the side facing the detector.The emission was then recorded with either the 790 nm or 405 nm laser blocked to record the reference and upconverted spectra, respectively.The emitted light passed through a 750 nm short pass filter (Thorlabs) before the detector.The intensity was recorded with a power meter (Thorlabs) and the spot size at the sample was determined using a beam profiler (Thorlabs).The quantum yield under 405 nm excitation was first determined for the films using an integrating sphere (described above) following the De Mello method. 23The photon upconversion quantum yield (Φ !" ) of the film was determined using the relative method using the relationship: Where Φ !NO is the quantum yield of fluorescence when exciting the films with 405 nm light, A $ is the absorption at excitation wavelength i, and  $ is the integrated emission intensity. =P,$ is the excitation photon flux at wavelength i.
Intensity dependence measurements where recorded in a similar manner attenuating the 790 nm excitation light using a graduated ND-filter.(Supplementary Figure 16), in agreement with the steady-state observation that effectively no triplet transfer is occurring.We extract QD excited state decay rates of 2.3 ± 0.2 µs -1 and 2.5 ± 0.   Compared to TA-CA the F-TA annihilator shows slightly higher lying singlet energies (Supplementary Figure 23).Likely the carboxylic acid group conjugates with the thienoanthracene core, extending the conjugation and lowering both the singlet and triplet energies of TA-CA relative to F-TA.

TEM of SF-PM films
PbS-TET-CA:Rubrene film blade coated from 2.5:10 mg/ml toluene.(b) Simulated grazing incidence scattering data for a ordered monolayer of QDs on the substrate surface, with corresponding real-space representation of this structure shown as an insert [generated using BornAgain software using a 2D interference lattice. 9] PbS-TA-CA:F-TA (b), (black circles) associated fits to an sphere*hard-sphere + FCC colloidal crystal model (red curves, with the separate sphere*hard-sphere (blue dashed line) and FCC colloidal crystal (small navy dots) components of the model fit.
probe beam from 520 to 950 nm.The second part of the PHAROS output is lead into a narrow band optical parametric oscillator system (ORPHEUS-LYRA, Light conversion) outputting the pump beam.The probe pulse is delayed up to 2 ns with a mechanical delay-stage (Newport).A mechanical chopper (Thorlabs) is used to create an on-off pump-probe pulse series.The pump size on the sample is approximately 0.065 mm 2 and the probe about 0.015 mm 2 .A silicon line scan camera (JAI SW-2000M-CL-80) fitted onto a visible spectrograph (Andor Solis, Shamrock) is used to record the transmitted probe light.

Figures
Figures S2 and S3show TEM images of PbS-OA:TIPS-Tc and PbS-TET-CA:TIPS-Tc films.The PbS-OA and PbS-TET-CA QDs displayed similar size distributions as imaged within TIPS-Tc films.PbS-OA showed

8. 4
Figure14).This IRF is shorter by 2 orders of magnitude than any of the time constants we observe in the triplet transfer processes.As such we treat the IRF as instantaneous relative to the dominant triplet transfer processes.

9. 1 Supplementary Figure 22 .
Energy Levels of AnthrathiophenesTo get an idea of the triplet energies of the thienoanthracenes we attached the TA-CA ligand to PbS QDs of different band gap and monitored the QD PL quenching.As can be seen in Supplementary Figure22significant quenching of ~50% is observed for QDs of bandgap 1.3 eV.Even greater quenching is observed for 1.4 eV QDs (~75%).Photoluminescence quantum efficiency (PLQE) of PbS QDs of different bandgap with oleic acid (OA) or TA-CA ligands, excited at 658 nm.

Table S4 :
Kinetic parameters obtained from fitting nanosecond transient absorption kinetics.Triplet intrinsic and transfer rates are calculated from fitting of mono-exponential functions to the TIPS-Tc triplet PIA at 865-980 nm, under 515 nm excitation at ~15 μJ/cm 2 .While the QD intrinsic decay rate is established from a mono-exponential fit to the GSB at 1120-1180 nm, under 658 nm excitation at ~15 μJ/cm 2 .The triplet exciton transfer efficiency,  <=< , is calculated from the ratio between the triplet transfer rate and the sum of all relevant triplet decay channels.

Table S7 .
Comparison of the triplet transfer kinetic parameters for a three-species model with global fitting to the intrinsic QD decay, triplet flux and QD PL from triplet transfer.The monomolecular TIPS-Tc triplet decay rate k1 and TIPS-Tc to PbS-TET-CA triplet transfer rate kTET1 are measured by fitting to the ns-TA.