Bi-Directional functionalization of urea-complexed SnO₂ for efficient planar perovskite solar cells

SnO₂ is regarded as the most promising electron transporting layer (ETL) material for perovskite solar cells (PSCs). Various functional groups are introduced onto the SnO₂ surface by interface modification with the purpose of improving the performance of the PSCs. However, most of the modifications are achieved in two-step approach, which are complicated and not easily realized. Here, we employ a facile one-step, low-temperature, and effective method to synthesis urea-complexed SnO₂ ETL (referred as Urea-SnO₂). The –NH₂ groups on Urea-SnO₂ attributes to facilitate the charge transfer within the SnO₂ ETL and reduce trap state density in the perovskite film through the chemical interactions. Therefore, The PSCs based on the Urea-SnO₂ ETL exhibit a champion power conversion efficiency (PCE) of 20.25%, which is more excellent than the devices based on the pristine SnO₂ ETL (17.60%). Functionalization of SnO₂ in situ by the precursor solution method offers an efficient method for high performance planar PSCs.