Ultrafast Carrier Dynamics in Methylammonium Lead Bromide

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Ultrafast Carrier Dynamics in Methylammonium Lead Bromide Perovskite Xiaofan Deng, Xiaoming Wen, Shujuan Huang, Rui Sheng, Takaaki Harada, Tak W. Kee, Martin A. Green, and Anita Wing-Yi Ho-Baillie J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b11640 • Publication Date (Web): 21 Jan 2016 Downloaded from http://pubs.acs.org on January 25, 2016

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The Journal of Physical Chemistry

Ultrafast Carrier Dynamics in Methylammonium Lead Bromide Perovskite Xiaofan Deng a, Xiaoming Wen a*, Shujuan Huang a, Rui Sheng a, Takaaki Harada b, Tak W. Kee b, Martin Green a, and Anita Ho-Baillie a a

Australian Centre for Advanced Photovoltaics, The University of New South Wales, Sydney, 2052, Australia b

Department of Chemistry, The University of Adelaide, Adelaide, 5005, Australia.

ABSTRACT The high open-circuit voltage of perovskite solar cell based on CH3NH3PbBr3 is suitable for a tandem system. It is important to understand the carrier dynamics to aid the optimisation of solar devices that are efficient in extracting the photo-generated carriers before they recombine. This work reports the ultrafast carrier dynamics in CH3NH3PbBr3 and test structures characterised by ultrafast transient absorption spectroscopy in the timescale of femto- and picoseconds. After laser excitation, the transient absorption signal at 534 nm is attributed to ground-state bleaching. The rise process with a time constant of hundreds of femtoseconds indicates fast cooling of hot carriers. The carrier population in the conduction band decreases subsequently and the decay has a fast and a slow component, which are ascribed to phonon assisted recombination and free electron-hole recombination, respectively. The shallow trap states result in a weak negative band in the low energy side of the band gap. Two weak positive features at ~507 nm and ~715 nm are assigned to excited state absorptions due to carriers and excitons, respectively. With a compact TiO2 (c-TiO2) electron

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transport layer, an increase in the light absorption is observed due to better quality of the CH3NH3PbBr3 film, resulting in higher photo-generated carrier density. We also elucidate the effective extraction of electrons by the c-TiO2 and estimate the electron transport time at CH3NH3PbBr3/c-TiO2 interface to be 0.68 ns.

Key Words: ultrafast spectroscopy, organic-inorganic perovskite, CH3NH3PbBr3, photovoltaics, carrier recombination

INTRODUCTION Organic-inorganic halide perovskite solar cells have recently emerged with remarkable power conversion efficiencies.1-4 Apart from device development, studies on photophysical processes are equally important for the understanding of device operation. Ultrafast spectroscopy has been proven to be a powerful method to investigate the charge carrier dynamics in materials and devices

5-8

, due

to the capability of monitoring dynamics of photoexcited carriers 9, such as photon absorption, vibrational relaxation and exciton generation and separation.7, 10-11 Most of the present investigations of ultrafast carrier dynamics are focused on the cells based on methylammonium lead iodide (CH3NH3PbI3) 5, 7, 9, 12-19. Using femtosecond transient absorption spectroscopy (fs-TAS), Xing et al. observed the hot carrier cooling process and demonstrated a balanced long electron-hole diffusion length (> 100 nm) in CH3NH3PbI3 which far surpasses those of typical low-temperature solutionprocessed photovoltaic materials 9. Wehrenfennig and his colleagues utilised time-resolved terahertz spectroscopy (TRTS) to reveal the high charge carrier motilities in CH3NH3PbI3 and CH3NH3PbI3xClx,

which are estimated to be about 11.6 and 8 cm2V-1s-1, respectively 18. Recently, Marchioro and

co-workers investigated the interfacial charge transfer dynamics by using fs-TAS and uncovered the


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electron injection process from CH3NH3PbI3 into TiO2 19. Manser and Kamat demonstrated the band filling effect in CH3NH3PbI3, in which the carrier injection modulates the bandgap of CH3NH3PbI3 5. To exceed the Shockley–Queisser limitation for high efficiency solar cells

20-21

, tandem device

architectures were proposed 22-27 .CH3NH3PbBr3 has a large bandgap (~2.3 eV) which is suitable for a tandem system

28

. However, the investigation and understanding of carrier dynamics in

CH3NH3PbBr3, important for device improvement, are lacking. In this work, we focus on ultrafast carrier dynamics in a bromide based perovskite solar cell material using fs-TAS. The photoexcitation and relaxation processes were firstly probed for a CH3NH3PbBr3 film deposited on a glass substrate. The carrier density dependent processes were studied by varying the pump fluence to uncover the carrier recombination mechanisms. To clarify the roles the charge transport layer in carrier dynamics, fs-TAS measurements were also performed on CH3NH3PbBr3/c-TiO2/Glass sample. After excitation, both photo-induced bleaching and absorption were observed. The investigation of the dynamics of the bleaching signal reveals the mechanism of thermalisation of hot carriers and carrier recombination in CH3NH3PbBr3 perovskite material. The extension of the bleaching signal at longer wavelength indicates the presence of shallow trap state. The two positive absorption bands reveal the coexistence of photo-generated carriers and excitons. By comparing the bleaching signals between two samples, it is suggested that a c-TiO2 layer has a positive effect on the both light absorption and carrier transportation in CH3NH3PbBr3 perovskite.

RESULTS AND DISCUSSION The CH3NH3PbBr3 perovskite films used in this experiment were fabricated on borosilicate glass substrates by vapour-assisted method

29

. The TA measurements were performed with a pump

wavelength of 400 nm. The details of sample preparation and measurement configuration are presented in the methods section. In this experiment, the dynamics due to by coherent responses, such as dephasing of exciton or biexciton, which are expected to be extremely fast as in other general semiconductors, may not be observable due to limited time resolution with 100 fs pulse duration.


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Figure 1a shows the absorption and photoluminescence (PL) spectra of CH3NH3PbBr3 film possessing a band gap of ~2.3 eV, consistent to previous reports

30-31

. Figure 1b shows an overview

of TA spectra for the CH3NH3PbBr3 film that represents the variation in optical density (OD) as a function of probe wavelength and delay time at a pump fluence of 50 µJ/cm2 per pulse (which corresponds to an injection level n0 ≈ 2×1018 cm-3 as estimated by Manser et al. 5. See Supplementary Information (SI) for more details). The positive and negative values of ∆OD represent the increase and reduction in transient absorption signals after pump pulse excitation, respectively 32.

Figure 1: (a) Absorption coefficient (black) and steady-state PL spectra (blue) of a CH3NH3PbBr3 film. (b) 2-dimensional pseudo-color map of transient absorption (TA) spectra expressed in ∆OD as functions of both delay time and probe wavelength for the CH3NH3PbBr3 film with pump wavelength of 400 nm and fluence of 50 µJ/cm2. (c) Evolution associated difference (EAD) spectra


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of the sample (with TA spectra of -1.1 ps as baseline). (d) Kinetic traces extracted from (b) at indicated wavelengths, and the inset is kinetic traces in short time window (0-5 ps) Three features are observable in Figure 1b; i) a strong negative feature (denoted as PB1) at 534 nm; ii) a narrow positive peak (PA1) at around 507 nm; and iii) a weak broad positive band (PA2) at 715 nm (note the ∆OD between 650 nm and 850nm in Figure 1b is scaled 10 times for clarity). Figure 1c shows the TA spectra with different time delays and Figure 1d presents ∆OD of each featured peak in term of delay time. The PB1 exhibits a much higher negative ∆OD. In fs-TAS, the electrons in the valence band (VB) of the sample are promoted to conduction band (CB) by the pump pulse. As the ground state is depleted of carriers, the ground-state absorption in the pumped sample is less than that in the non-pumped sample resulting in negative ∆OD. Given the PB1 is very close to the material optical gap (~536 nm, see Figure 1a), it can be ascribed to ground-state bleaching. The inset in Figure 1d reveals further details of the processes. The PB1 is formed in the first few picoseconds after photoexcitation as a result of ground-state bleaching. This reduction in ∆OD has been widely observed as the thermalisation of hot carriers

7, 16

. Under a 400 nm (3.1 eV) pump excitation, hot

electron–hole pairs are generated in the high excited states. The hot carriers rapidly relax to quasithermal equilibrium states, mainly by longitudinal optical (LO) phonon scattering, resulting in statefilling at the bottom of the conduction band 5, 9. This process is usually very fast, within picoseconds, by LO phonon scattering 33-35. To explore detailed mechanisms of carrier dynamics, normalised kinetic traces of PB1 under various pump fluences are plotted in Figure 2a. The sign of the ∆OD is inverted with the focus being the magnitude of the ∆OD. These kinetic traces are fitted with the equation ∆OD = (− / +

∑ / ) 36, in which is the peak value of ∆OD that the signal could reach, is the rise time constant, is the decay time constants of each decay component, respectively, and is the proportions of each decay component comprised in total signal. Figure 2b shows the rise time constant and the amplitude of the ∆OD as a function of pump fluence. For the rise time constants


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increase with pump fluence when it is below 50 µJ/cm2. It has been previously reported that the cooling rate of hot carriers is reduced with an increase of pump fluence in perovskite materials and other semiconductors

35, 37-38

. It is due to the generation of hot optical phonons during the cooling

process that slows the subsequent cooling of carriers 35, 37-38. Under high intensities, the ground state bleaching dynamics behave similarly indicating the saturation of the band edge states. Therefore the carrier density in the edge of the conduction band does not further increase. The evidence is the similar amplitudes between the bleaching with pump fluence of 50 and 100 µJ/cm2, as shown in Figure 2b.

Figure 2: (a) Normalised and inverted kinetic traces of ground-state bleaching (534 nm) under different pump fluence,; (b) Rise time constant and amplitude of the 534 nm dynamic as a function of pump fluence; and (c) Decay time constant and proportion of fast decay component of the 534 nm dynamic as a function of pump fluence The decay dynamics of PB1 consist of fast and slow components, which were extracted from the fitting (i.e. in the fitting equation equal to 2). The decay dynamics depend on excitation intensity below 50 µJ/cm2. The fast components τ2 and their proportions are plotted in Figure 2c. Typically, phonon scattering and Auger recombination contribute to the fast component τ2 8. At low carrier density the phonon assisted recombination (defect trapping) dominates τ2 while Auger recombination is negligible. As pump flunce increases from 2 to 50 µJ/cm2, τ2 significantly reduces from 248 to 86 ps while the proportion of the fast decay component increases from 17 to 47%. The increasingly dominant fast decay component under increasing excitation fluence is due to Auger recombination 16.


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The time constants of the slow components τ3 are large in nanoseconds scale, as listed in Table S2, which can be attributed to free electron-hole recombination, as reported in previous work

29

. It

should be noted that the time constant of the slow component is larger than the time window of the current experiment. Concurrent with the ground-state bleaching, the TA spectra in Figure 1b shows a weak and broad bleaching band (PB2) from 580 to 650 nm that has faster recovery kinetics compared to ground-state bleaching (Figure 1d).

Basically, TA signal represents a variation of population occupation

with a given detection level 39. Considering the energy relation with the band gap, the negative band is most likely due to shallow trap states present in the CH3NH3PbBr3 film. Wu and his colleagues applied fs-TAS measurement to CH3NH3PbI3 and attributed the broad distributed weak bleaching below the optical gap to the effect of traps transition from the ground states

40

. The unoccupied trap states permit weak optical

41

, resulting in optical absorption before photo-excitation. Under

pump excitation the trap states have already been populated, thus reduced ∆OD is expected. Figure 1b and 1c also show two excited state absorption peaks, PA1 and PA2 10. After fitting, both the growth and decay processes of PA1 have comparable time constants with the ground-state bleaching dynamics of PB1. It suggests the two features have the same origin which is attributed to state-filling by excited carriers

9, 42

. However, it is evident that the rise dynamics of PA2 are very

different from those of the bleaching band, as shown in the inset of Figure 1d. The much faster (~0.16 ps) rise of PA2 indicates a different origin from bleaching 10, which is most likely to be the absorption of photo-generated excitons for several reasons. Reported exciton binding energy of CH3NH3PbBr3 perovskite ranges from 40 to 150 meV 43-45, larger than thermal energy (~26 meV) at room temperature. Therefore it is reasonable that photo-generated excitons coexist (exciton may not dominant due to its fraction also affected by exciton-exciton interaction and effect of grain boundaris other than binding energy

46-47

) with free carriers

16

. Under an excitation fluence of 50 µJ/cm2, the

amplitude of PA2 is only about 3% (Figure 1d), suggesting excitons only make a small contribution


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to photo-generated carriers compared to free carriers. The observation is consistent with the investigation by Saba et. al. ,that although with high excitation intensity the main photogerenation species is free charge carrier due to many-body effects48. Sheng et al. also attributed a similar absorption band after photo-excitation of CH3NH3PbI3 to generation of exciton 10. The ~100 fs rise time of PA2 also corresponds to exciton generation time as determined by recent work on CH3NH3PbI3 by Piatkowski et al.14. To clarify the roles of an electron transport layer in carrier dynamics, the fs-TAS measurements were also performed on the CH3NH3PbBr3 with an electron transport layer c-TiO2. The pump laser was incident on the surface of CH3NH3PbBr3 film. Figure 3a compares the TA spectra of the CH3NH3PbBr3 sample and the CH3NH3PbBr3/c-TiO2 sample under a pump fluence of 50 µJ/cm2. Both samples exhibit similar features in the TA spectra in the visible region. However, the bleaching amplitude in CH3NH3PbBr3/c-TiO2 is larger than that in the CH3NH3PbBr3 sample. This is due to a higher quality CH3NH3PbBr3 film on c-TiO2 layer (and hence better absorption) compared to CH3NH3PbBr3 deposited on glass only

49-50

. The rise time constants of those samples show very

similar trends in Figure 3b, suggesting that c-TiO2 layer has insignificant influence on ground-state bleaching dynamics. However, the faster decay kinetics of ground-state bleaching in CH3NH3PbBr3/c-TiO2 sample was observable in Figure 3c as a result of the injection of photogenerated electrons from CH3NH3PbBr3 to the c-TiO2 layer.


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Figure 3: (a) EAD of CH3NH3PbBr3 and CH3NH3PbBr3/c-TiO2 at a delay time of 21 ps under pump fluence of 50 µJ/cm2; (c) Normalised and inverted kinetic traces of the 534-nm dynamics for CH3NH3PbBr3 and CH3NH3PbBr3/c-TiO2. (b) Rise and (d) decay time constants extracted from the 534-nm kinetic traces for CH3NH3PbBr3 and CH3NH3PbBr3/c-TiO2 when changing the pump fluence. In this case to clarify the carrier transport process, we compare the effective decay time in both CH3NH3PbBr3 and CH3NH3PbBr3/c-TiO2 samples, where effective decay time is defined as τ = ∑ τ 51 . ∑ τ

The and τ represent the proportion and time constant of each decay component,

respectively. From the change of effective decay time of ground-state bleaching after applying cTiO2 layer (Figure 3d), the carrier transport time through CH3NH3PbBr3/c-TiO2 interface is estimated by τ

!"#$%&"

=τ

'"#(/)*

−τ

'"#(

7, 52

, where τ+,-/./ and τ+,- are the effective decay time

constants for CH3NH3PbBr3/c-TiO2 and CH3NH3PbBr3, respectively. The calculated interfacial


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transport time is 0.68 ns which is in good agreement with the electron transport time previously reported for CH3NH3PbI3/c-TiO2 or CH3NH3PbI3/PCBM interface

16, 52

. Therefore, our experiments

show the important role of c-TiO2 layer that both improves the quality of fabrication of perovskite layer and facilitates the effective electron transportation.

CONCLUSION In this work, the ultrafast carrier dynamics in CH3NH3PbBr3 have been investigated by utilising ultrafast transient absorption spectroscopy. The ground-state bleaching is observed at 534 nm and two weak positive features at 507 nm and 715 nm are assigned to the transition of photo-generated carriers and excitons, respectively. The experiment confirmed a sub-picosecond hot carrier thermalisation process in CH3NH3PbBr3 film. With a low pump intensity, free electron-hole recombination is the dominant recombination mechanism in this material while phonon assisted recombination mechanism is also observed with a time constant of hundreds of picosecond. When injection level is high, Auger recombination dominates the decay kinetics. The peak observed at 615 nm (~2.0 eV) suggests the presence of trap state that is very shallow and is only ~0.3 eV from conduction band or valence band. When compact TiO2 is presence, the larger bleaching amplitude supports that the TiO2 layer improves the quality of perovskite for better light absorption. More importantly, c-TiO2 layer efficiently collects the excited electrons within ~0.68 ns. The investigation provides an understanding of the carrier relaxation and transportation dynamics in CH3NH3PbBr3 to further optimise the related devices with CH3NH3PbBr3 as light harvesting material.

METHODS 4.1 Sample preparation All samples were deposited on borosilicate glass substrates. The substrates were cleaned by 2% Hallmanex detergent, acetone and isopropanol in an ultrasonic bath for 10 min in each cleaning agent followed by UVO treatment for 10 min. For the sample structure of glass/c-TiO2/perovskite, c-TiO2


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layer was deposited by spin-coating a mildly acidic solution of titanium isopropoxide in ethanol at 2000 rpm for 60 s followed by annealing at 500 °C for 30 min. All CH3NH3PbBr3 films were fabricated by vapour-assisted method 29. Firstly, PbBr2 solution in DMF with a concentration of 1 M was spin-coated on the mp-TiO2 at 2000 rpm for 60 s. After annealing at 70°C for 30 min, the film was treated by CH3NH3Br vapour at 175 °C for 10 min in a closed glass petri-dish with CH3NH3Br powder surrounded on a hotplate in a glovebox, then rinsed in isopropanol at room temperature.

4.2 Spectroscopic measurement The femtosecond pump-probe transient absorption experiments were performed with a transient absorption spectrometer (Helios, Ultrafast Systems). The laser system is a regenerative amplifier (800 nm with a repetition rate of 1 kHz and pulse duration of 100 fs) seeded by a Ti:Sapphire oscillator. The output of the amplifier was then split into pump and probe beamlines. The 400 nm pump pulses were generated using a BBO crystal. The probe beam passed through a delay stage and was used to generate a white light continuum in a sapphire crystal. The pump fluence was attenuated to between 2 and 100 µJ/cm2. The experiment was performed at room temperature.

SUPPLEMENTARY INFORMATION The Supplementary Information is available free via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]

ACKNOWLEDGEMENTS The Australian Centre for Advanced Photovoltaics (ACAP) encompasses the Australian-based activities of the Australia-US Institute for Advanced Photovoltaics (AUSIAPV) and is supported by the Australian Government through the Australian Renewable Energy Agency (ARENA).


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REFERENCES 1. Green, M. A.; Ho-Baillie, A.; Snaith, H. J., The Emergence of Perovskite Solar Cells. Nature Photonics 2014, 8, 506. 2. Liu, M.; Johnston, M. B.; Snaith, H. J., Efficient Planar Heterojunction Perovskite Solar Cells by Vapour Deposition. Nature 2013, 501, 395. 3. Docampo, P.; Ball, J. M.; Darwich, M.; Eperon, G. E.; Snaith, H. J., Efficient Organometal Trihalide Perovskite Planar-Heterojunction Solar Cells on Flexible Polymer Substrates. Nat. Comm. 2013, 4, 2761. 4. Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J., Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites. Science 2012, 338, 643. 5. Manser, J. S.; Kamat, P. V., Band Filling with Free Charge Carriers in Organometal Halide Perovskites. Nature Photonics 2014, 8, 737. 6. Ponseca, C. S., Jr., et al., Organometal Halide Perovskite Solar Cell Materials Rationalized: Ultrafast Charge Generation, High and Microsecond-Long Balanced Mobilities, and Slow Recombination. J. Am. Chem. Soc. 2014, 136, 5189. 7. Hsu, H. Y.; Wang, C. Y.; Fathi, A.; Shiu, J. W.; Chung, C. C.; Shen, P. S.; Guo, T. F.; Chen, P.; Lee, Y. P.; Diau, E. W. G., Femtosecond Excitonic Relaxation Dynamics of Perovskite on Mesoporous Films of Al2o3 and Nio Nanoparticles. Angewandte Chemie 2014, 126, 9493. 8. Wen, X.; Yu, P.; Toh, Y. R.; Hao, X.; Tang, J., Intrinsic and Extrinsic Fluorescence in Carbon Nanodots: Ultrafast Time-Resolved Fluorescence and Carrier Dynamics. Advanced Optical Materials 2013, 1, 173. 9. Xing, G.; Mathews, N.; Sun, S.; Lim, S. S.; Lam, Y. M.; Grätzel, M.; Mhaisalkar, S.; Sum, T. C., LongRange Balanced Electron-and Hole-Transport Lengths in Organic-Inorganic Ch3nh3pbi3. Science 2013, 342, 344. 10. Sheng, C.; Zhang, C.; Zhai, Y.; Mielczarek, K.; Wang, W.; Ma, W.; Zakhidov, A.; Vardeny, Z. V., Exciton Versus Free Carrier Photogeneration in Organometal Trihalide Perovskites Probed by Broadband Ultrafast Polarization Memory Dynamics. Physical review letters 2015, 114, 116601. 11. Leguy, A. M.; Frost, J. M.; McMahon, A. P.; Sakai, V. G.; Kochelmann, W.; Law, C.; Li, X.; Foglia, F.; Walsh, A.; O’Regan, B. C., The Dynamics of Methylammonium Ions in Hybrid Organic-Inorganic Perovskite Solar Cells. Nat. Comm. 2015, 6, 7124. 12. Giovanni, D.; Ma, H.; Chua, J.; Grätzel, M.; Ramesh, R.; Mhaisalkar, S.; Mathews, N.; Sum, T. C., Highly Spin-Polarized Carrier Dynamics and Ultralarge Photoinduced Magnetization in Ch3nh3pbi3 Perovskite Thin Films. Nano letters 2015, 15, 1553. 13. Guo, Z.; Manser, J. S.; Wan, Y.; Kamat, P. V.; Huang, L., Spatial and Temporal Imaging of Long-Range Charge Transport in Perovskite Thin Films by Ultrafast Microscopy. Nature communications 2015, 6. 14. Piatkowski, P.; Cohen, B.; Ramos, F. J.; Di Nunzio, M.; Nazeeruddin, M. K.; Grätzel, M.; Ahmad, S.; Douhal, A., Direct Monitoring of Ultrafast Electron and Hole Dynamics in Perovskite Solar Cells. Physical Chemistry Chemical Physics 2015, 17, 14674. 15. Wu, X.; Trinh, M. T.; Zhu, X.-Y., Excitonic Many-Body Interactions in Two-Dimensional Lead Iodide Perovskite Quantum Wells. The Journal of Physical Chemistry C 2015, 119, 14714. 16. Sum, T. C.; Mathews, N., Advancements in Perovskite Solar Cells: Photophysics Behind the Photovoltaics. Energy & Environmental Science 2014, 7, 2518. 17. Malinkiewicz, O.; Yella, A.; Lee, Y. H.; Espallargas, G. M.; Graetzel, M.; Nazeeruddin, M. K.; Bolink, H. J., Perovskite Solar Cells Employing Organic Charge-Transport Layers. Nature Photonics 2014, 8, 128. 18. Wehrenfennig, C.; Eperon, G. E.; Johnston, M. B.; Snaith, H. J.; Herz, L. M., High Charge Carrier Mobilities and Lifetimes in Organolead Trihalide Perovskites. Advanced Materials 2014, 26, 1584. 19. Marchioro, A.; Teuscher, J.; Friedrich, D.; Kunst, M.; Van De Krol, R.; Moehl, T.; Grätzel, M.; Moser, J.E., Unravelling the Mechanism of Photoinduced Charge Transfer Processes in Lead Iodide Perovskite Solar Cells. Nature photonics 2014, 8, 250. 20. Green, M. A., Third Generation Photovoltaics: Ultra-High Conversion Efficiency at Low Cost. Progress in Photovoltaics 2001, 9, 123. 21. Green, M. A., Analytical Treatment of Trivich-Flinn and Shockley-Queisser Photovoltaic Efficiency Limits Using Polylogarithms. Progress in Photovoltaics 2012, 20, 127.


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22. Rühle, S.; Segal, A.; Vilan, A.; Kurtz, S. R.; Grinis, L.; Zaban, A.; Lubomirsky, I.; Cahen, D., A Two Junction, Four Terminal Photovoltaic Device for Enhanced Light to Electric Power Conversion Using a LowCost Dichroic Mirror. Journal of Renewable and Sustainable Energy 2009, 1, 013106. 23. Löper, P.; Moon, S.-J.; De Nicolas, S. M.; Niesen, B.; Ledinsky, M.; Nicolay, S.; Bailat, J.; Yum, J.-H.; De Wolf, S.; Ballif, C., Organic–Inorganic Halide Perovskite/Crystalline Silicon Four-Terminal Tandem Solar Cells. Physical Chemistry Chemical Physics 2015, 17, 1619. 24. Mailoa, J. P.; Bailie, C. D.; Johlin, E. C.; Hoke, E. T.; Akey, A. J.; Nguyen, W. H.; McGehee, M. D.; Buonassisi, T., A 2-Terminal Perovskite/Silicon Multijunction Solar Cell Enabled by a Silicon Tunnel Junction. Applied Physics Letters 2015, 106, 121105. 25. Bailie, C. D.; Christoforo, M. G.; Mailoa, J. P.; Bowring, A. R.; Unger, E. L.; Nguyen, W. H.; Burschka, J.; Pellet, N.; Lee, J. Z.; Grätzel, M., Semi-Transparent Perovskite Solar Cells for Tandems with Silicon and Cigs. Energy & Environmental Science 2015, 8, 956. 26. Uzu, H.; Ichikawa, M.; Hino, M.; Nakano, K.; Meguro, T.; Hernández, J. L.; Kim, H.-S.; Park, N.-G.; Yamamoto, K., High Efficiency Solar Cells Combining a Perovskite and a Silicon Heterojunction Solar Cells Via an Optical Splitting System. Applied Physics Letters 2015, 106, 013506. 27. Todorov, T.; Gershon, T.; Gunawan, O.; Sturdevant, C.; Guha, S., Perovskite-Kesterite Monolithic Tandem Solar Cells with High Open-Circuit Voltage. Applied Physics Letters 2014, 105, 173902. 28. Sheng, R.; Ho-Baillie, A. W.-Y.; Huang, S.; Keevers, M.; Hao, X.; Jiang, L.; Cheng, Y.-B.; Green, M. A., 4Terminal Tandem Solar Cells Using Ch3nh3pbbr3 by Spectrum Splitting. The Journal of Physical Chemistry Letters 2015, 6, 3931. 29. Sheng, R.; Ho-Baillie, A.; Huang, S.; Chen, S.; Wen, X.; Hao, X.; Green, M. A., Methylammonium Lead Bromide Perovskite-Based Solar Cells by Vapour-Assisted Deposition. J Phys. Chem. C 2015, 119, 3545. 30. Wen, X.; Ho-Baillie, A.; Huang, S.; Sheng, R.; Chen, S.; Ko, H.; Green, M. A., Mobile Charge Induced Fluorescence Intermittency in Methylammonium Lead Bromide Perovskite. Nano Lett. 2015, 15, 4644. 31. Zhang, M.; Yu, H.; Lyu, M.; Wang, Q.; Yun, J.-H.; Wang, L., Composition-Dependent Photoluminescence Intensity and Prolonged Recombination Lifetime of Perovskite CH3NH3PbBr3-xClx Films. Chem. Commun. 2014, 50, 11727. 32. Wen, X.; Yu, P.; Toh, Y.-R.; Lee, Y.-C.; Huang, K.-Y.; Huang, S.; Shrestha, S.; Conibeer, G.; Tang, J., Ultrafast Electron Transfer in the Nanocomposite of the Graphene Oxide–Au Nanocluster with Graphene Oxide as a Donor. Journal of Materials Chemistry C 2014, 2, 3826. 33. Mueller, M. L.; Yan, X.; Dragnea, B.; Li, L.-s., Slow Hot-Carrier Relaxation in Colloidal Graphene Quantum Dots. Nano letters 2010, 11, 56. 34. Klimov, V. I.; McBranch, D. W., Femtosecond 1 P-to-1 S Electron Relaxation in Strongly Confined Semiconductor Nanocrystals. Physical Review Letters 1998, 80, 4028. 35. Low, T.; Perebeinos, V.; Kim, R.; Freitag, M.; Avouris, P., Cooling of Photoexcited Carriers in Graphene by Internal and Substrate Phonons. Physical Review B 2012, 86, 045413. 36. Wu, K.; Liang, G.; Shang, Q.; Ren, Y.; Kong, D.; Lian, T., Ultrafast Interfacial Electron and Hole Transfer from Cspbbr3 Perov-Skite Quantum Dots. Journal of the American Chemical Society 2015, 137, 12792. 37. Wang, H.; Strait, J. H.; George, P. A.; Shivaraman, S.; Shields, V. B.; Chandrashekhar, M.; Hwang, J.; Rana, F.; Spencer, M. G.; Ruiz-Vargas, C. S., Ultrafast Relaxation Dynamics of Hot Optical Phonons in Graphene. Applied Physics Letters 2010, 96, 081917. 38. Price, M. B.; Butkus, J.; Jellicoe, T. C.; Sadhanala, A.; Briane, A.; Halpert, J. E.; Broch, K.; Hodgkiss, J. M.; Friend, R. H.; Deschler, F., Hot-Carrier Cooling and Photoinduced Refractive Index Changes in OrganicInorganic Lead Halide Perovskites. Nature Communications 2015, 6, 8420. 39. Wen, X.; Davis, J.; McDonald, D.; Dao, L.; Hannaford, P.; Coleman, V.; Tan, H.; Jagadish, C.; Koike, K.; Sasa, S., Ultrafast Dynamics in Zno/Znmgo Multiple Quantum Wells. Nanotechnology 2007, 18, 315403. 40. Wu, X.; Trinh, M. T.; Niesner, D.; Zhu, H.; Norman, Z.; Owen, J. S.; Yaffe, O.; Kudisch, B. J.; Zhu, X.-Y., Trap States in Lead Iodide Perovskites. Journal of the American Chemical Society 2015, 137, 2089. 41. Skandan, G.; Singhal, A.; Contescu, C.; Putyera, K., Dekker Encyclopedia of Nanoscience and Nanotechnology; Taylor & Francis: New York, 2009, p 668.


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Page 14 of 15

42. Stranks, S. D.; Eperon, G. E.; Grancini, G.; Menelaou, C.; Alcocer, M. J.; Leijtens, T.; Herz, L. M.; Petrozza, A.; Snaith, H. J., Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber. Science 2013, 342, 341. 43. Tanaka, K.; Takahashi, T.; Ban, T.; Kondo, T.; Uchida, K.; Miura, N., Comparative Study on the Excitons in Lead-Halide-Based Perovskite-Type Crystals CH3NH3PbBr3 CH3NH3PbI3. Solid state communications 2003, 127, 619. 44. Koutselas, I.; Ducasse, L.; Papavassiliou, G. C., Electronic Properties of Three-and Low-Dimensional Semiconducting Materials with Pb Halide and Sn Halide Units. Journal of Physics: Condensed Matter 1996, 8, 1217. 45. Yang, Y.; Yang, M.; Li, Z.; Crisp, R.; Zhu, K.; Beard, M. C., Comparison of Recombination Dynamics in CH3NH3PbBr3 and CH3NH3PbI3 Perovskite Films: Influence of Exciton Binding Energy. The journal of physical chemistry letters 2015, 6, 4688. 46. D’Innocenzo, V.; Grancini, G.; Alcocer, M. J.; Kandada, A. R. S.; Stranks, S. D.; Lee, M. M.; Lanzani, G.; Snaith, H. J.; Petrozza, A., Excitons Versus Free Charges in Organo-Lead Tri-Halide Perovskites. Nature communications 2014, 5, 3586. 47. Jeong, A.; Jo, W.; Jung, S.; Gwak, J.; Yun, J., Enhanced Exciton Separation through Negative Energy Band Bending at Grain Boundaries of Cu2znsnse4 Thin-Films. Applied Physics Letters 2011, 99, 082103. 48. Saba, M.; Cadelano, M.; Marongiu, D.; Chen, F.; Sarritzu, V.; Sestu, N.; Figus, C.; Aresti, M.; Piras, R.; Lehmann, A. G., Correlated Electron–Hole Plasma in Organometal Perovskites. Nature communications 2014, 5, 5049. 49. Yin, W.-J.; Yang, J.-H.; Kang, J.; Yan, Y.; Wei, S.-H., Halide Perovskite Materials for Solar Cells: A Theoretical Review. Journal of Materials Chemistry A 2015, 3, 8926. 50. Mosconi, E.; Ronca, E.; De Angelis, F., First-Principles Investigation of the Tio2/Organohalide Perovskites Interface: The Role of Interfacial Chlorine. The Journal of Physical Chemistry Letters 2014, 5, 2619. 51. Kapusta, P.; Macháň, R.; Benda, A.; Hof, M., Fluorescence Lifetime Correlation Spectroscopy (Flcs): Concepts, Applications and Outlook. International journal of molecular sciences 2012, 13, 12890. 52. Ogomi, Y.; Kukihara, K.; Qing, S.; Toyoda, T.; Yoshino, K.; Pandey, S.; Momose, H.; Hayase, S., Control of Charge Dynamics through a Charge-Separation Interface for All-Solid Perovskite-Sensitized Solar Cells. ChemPhysChem 2014, 15, 1062.


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Ultrafast Carrier Dynamics in Methylammonium Lead Bromide

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