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.