Stable high-performance perovskite solar cells based on inorganic electron transporting bi-layers

As one of the significant electron transporting materials (ETMs) in efficient planar heterojunction perovskite solar cells (PSCs), SnO₂ can collect/transfer photo-generated carriers produced in perovskite active absorbers and suppress the carrier recombination at interfaces. In this study, we demonstrate that a mild solution-processed SnO₂ compact layer can be an eminent ETM for planar heterojunction PSCs. Here, the device based on chemical-bath-deposited SnO₂ electron transporting layer (ETL) exhibits a power conversion efficiency (PCE) of 16.10% and with obvious hysteresis effect (hysteresis index = 19.5%), owing to the accumulation and recombination of charge carriers at the SnO₂/perovskite interface. In order to improve the carrier dissociation and transport process, an ultrathin TiO₂ film was deposited on the top of the SnO₂ ETL passivating nonradiative recombination center. The corresponding device based on the TiO₂@SnO₂ electron transporting bi-layer (ETBL) exhibited a high PCE (17.45%) and a negligible hysteresis effect (hysteresis index = 1.5%). These findings indicate that this facile solution-processed TiO₂@SnO₂ ETBL paves a scalable and inexpensive way for fabricating hysteresis-less and high-performance PSCs.