Charge carrier dynamics in organometal halide perovskite materials probed using time-resolved THz spectroscopy

Villy Sundström^a, Tonu Pullerits^a, Arkady Yartsev^a, Kaibo Zheng^a, Mohamed Abdellah^a, Carlito Jr Ponseca^a

^aLund University, Sweden, Kämnärsvägen 10H, Lund, 22645, Sweden

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Oral, Carlito Jr Ponseca, presentation 130
Publication date: 5th February 2015

Understanding of the fundamental photophysical properties of perovskite solar cell materials, despite gaining much attention due to its very high overall power conversion efficiency, has remained scarce. By using time resolved terahertz (THz) spectroscopy, we report the charge carrier dynamics of solution-processed CH₃NH₃PbI₃ perovskite materials. Ultrafast rise in the THz photoconductivity kinetics suggests charge species being generated almost instantaneously after photoexcitation. A second step rise of the THz kinetics signal is shown and lasts from few ps to several nanoseconds depending on the excitation intensity. Perovskite/Al₂O₃ blends have almost balanced electron and hole mobilities (μ_e= 12.5 cm²V^-1s^-1, μ_h= 7.5 cm²V^-1s^-1) and remain very high up to a nanosecond. When the perovskite is introduced into a TiO₂ mesoporous structure, electron injection from perovskite to the metal oxide is efficient in less than a picosecond but the lower intrinsic electron mobility of TiO2 (μ < 0.1 cm²V^-1s^-1) leads to unbalanced charge transport.¹ These results unravels the remarkable intrinsic properties of this perovskite material if used as intrinsic light absorber and charge transport layer. Moreover, finding a metal oxide with higher electron mobility may further increase the performance of this class of solar cells.
THz photoconductivity kinetics for the first 50 ps normalized with excitation intensity.
1. Ponseca, C. S., Jr.; Savenije, T. J.; Abdellah, M.; Zheng, K.; Yartsev, A.; Pascher, T.; Harlang, T.; Chabera, P.; Pullerits, T.; Stepanov, A.; Wolf, J.; Sundstrom, V. Organometal Halide Perovskite Solar Cells Explained-Ultrafast Charge Generation, High and Microsecond-Long Balanced Mobilities and Slow Recombination. J. Am. Chem. Soc.2014, 136, 5189−5192.

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