The trap-state density in perovskite films largely determines the photovoltaic performance of perovskite solar cells (PSCs). Increasing the crystal grain size in perovskite films is an effective method to reduce the trap-state density. Here, we have added NH4SCN into perovskite precursor solution to obtain perovskite films with an increased crystal grain size. The perovskite with increased crystal grain size shows a much lower trap-state density compared with reference perovskite films, resulting in an improved photovoltaic performance in PSCs. The champion photovoltaic device has achieved a power conversion efficiency of 19.36%. The proposed method may also impact other optoelectronic devices based on perovskite films.

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Published in Nanoscale Research Letters, v. 14, 304, p. 1-7.

© The Author(s). 2019

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This work was supported by the National Natural Science Foundation of China under Grant Nos. 61874150, 61421002, and 61574029. This work was also partially supported by the University of Kentucky.