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

SnO 2 is regarded as the most promising electron transporting layer (ETL) material for perovskite solar cells (PSCs). Various functional groups are introduced onto the SnO 2 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 SnO 2 ETL (referred as Urea-SnO 2 ). The –NH 2 groups on Urea-SnO 2 attributes to facilitate the charge transfer within the SnO 2 ETL and reduce trap state density in the perovskite film through the chemical interactions. Therefore, The PSCs based on the Urea-SnO 2 ETL exhibit a champion power conversion efficiency (PCE) of 20.25%, which is more excellent than the devices based on the pristine SnO 2 ETL (17.60%). Functionalization of SnO 2 in situ by the precursor solution method offers an efficient method for high performance planar PSCs.