Suppressing charge recombination in planar perovskite solar cells by using SnO2/TiO2 nanocomposite as electron transfer layer

Hybrid perovskite solar cells (PSCs) have been paid great attention owing to their excellent photovoltaic properties. However, the presence of charge recombination at the interface of the electron transport layer (ETL)/perovskite hinders the performance of perovskite solar cells, preventing them from reaching the Shockley–Queisser limit. Herein, the SnO2/TiO2 nanoparticles (NPs) composite (S/T-NC) ETL is developed by adopting a simple method at low temperature and applied into planar PSCs. Our results show that the maximum power conversion efficiency of PSCs based on the S/T-NC ETL is 20.51% with a VOC of 1.09 V, a JSC of 24.15 mA/cm2, and a fill factor of 77.84%, much higher than that for both SnO2 NPs based PSCs (18.19%) and TiO2 NPs based PSCs (17.81%). Further analysis reveals that the mixing of TiO2 and SnO2 can improve film quality and reduce trap density, thus, suppressing charge recombination and improving stability. These findings prove that the use of SnO2/TiO2 composite ETL is an effective way to further improve the performance for planar PSCs.