Tracing Trapped Carrier Dynamic in Perovskite Solar Cell Via IR Optical Activation Spectroscopy
Jiaxin Pan a, Ziming Chen a, Tiankai Zhang b, Beier Hu a, Feng Gao b, Artem Bakulin a, Piers Barnes c
a Ultrafast Optoelectronics Group, Imperial College London
b Linköping University, Bredgatan, 33, Norrköping, Sweden
c Imperial College London, Exhibition Road, United Kingdom
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Poster, Jiaxin Pan, 206
Publication date: 20th April 2022

In perovskite solar cells (PSCs), trap states are considered one of the main factors limiting the device performance (e.g., open-circuit voltage and short-circuit current) as they reduce the mobility of photogenerated carriers and cause trap-assisted recombination [1]. In such a case, trap passivation becomes a popular method to boost device performance, and reports show that passivating surface traps of perovskite become more effective than passivating their bulk traps. Material scientists attribute the better effect of surface passivation to the significant reduction of trap density in perovskites since the majority amount of traps state are considered located at the perovskite surface. We report a pump-push photocurrent spectroscopy study, which is able to trace the dynamics of trapped carriers using a delayed infrared push pulse to bring carriers from defect states to the conduction band. We found that the trapping time as well as recombination time for trapped states are dominan  t factors towards the device performance of PSCs[2].  Via investigating the lifetime of FAPI solar cells with and without surface passivation, we observed that carriers in surface traps recombine much faster than that in bulk traps, illustrating that surface defects have a much higher possibility to re-trap carriers generated under continuous light illumination. With such a clearer understanding of the trapped carrier dynamics, we anticipate our assay to be another starting point for material scientists to further improve existing PSC performance.

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