Crystallization Kinetics of a-FAPbI3-based Perovskite Solar Cells and High Stability Enabled by ALD (Atomic Layer Deposition)
Hyunjung Shin a b
a Department of Energy Science, Sungkyunkwan University, Suwon, South Korea
b SKKU Institute of Energy Science & Technology (SIEST), Sungkyunkwan University, Suwon, South Korea
Invited Speaker, Hyunjung Shin, presentation 065
Publication date: 21st November 2022

Power conversion efficiency (PCE) of perovskite solar cells (PSCs) has increased dramatically and has reached to 25.7%. For even higher PCE, the increase of open-circuit voltage (Voc) as well as fill factor (FF) will be a main challenge to be solved since the short circuit current density (Jsc) is almost approaching the theoretical limit (i.e., 28.97 mAcm-2). The reason for low Voc and FF must be related with the energy loss of charge carriers which is originated from the recombination through defects, inefficient charge extraction from the absorbers on the surfaces/interfaces, and current leakage through shunt paths. As recent studies reported incorporation of methylammonium chloride (MACl) to stabilize α-FAPbI3, herein, we propose that crystallization process of α-FAPbI3 can be kinetically controlled by adjusting MACl concentration. We examined higher concentration of MACl induces slower crystallization kinetics, resulting in larger grain size and [100] preferred orientation. This indicates the impact of controlling the crystallization kinetics to result a preferred orientation and a large grain size, which leads to high PCEs. Furthermore, we present an amorphous TiO2 and V2O5-x passivation layers, deposited by atomic layer deposition (ALD) at low temperature (< 50 ℃), on Spiro-OMeTAD to prevent metal-induced interfacial degradation while maintaining the overall performance. Finally, we have fabricated perovskite solar cells (FTO/SnO2-based ALD-ETL/FAPbI3/2Dperovskite/Spiro-OMeTAD/Au) and confirmed increased PCE (23.91 %) measured under AM 1.5 G. Not only PCE, but also device stability with ALD-TiO2 and V2O5-x layers was dramatically improved. It was confirmed through ion contents profiling using ToF-SIMS that the improvement of the stability in PSC adopting ALD-TiO2 and V2O5-x comes from preventing the metal ion diffusion. In conclusion, we have demonstrated high PCE and stability of PSCs. 

This work was financially supported by the National Research Foundation of Korea (NRF) grants funded by the Ministry of Science; under contracts with grant no. NRF-2019R1A2C3009157, NRF-2018K1A3A1A32055268, 2018M3C1B7021994. This work was also partly supported by Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government (MOTIE) (20203040010320).

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