Room-temperature synthesized SnO 2 electron transport layers for efficient perovskite solar cells.

Tin oxide (SnO 2 ) is widely used as electron transport layer (ETL) material in perovskite solar cells (PSCs). Numerous synthesis methods for SnO 2 have been reported, but they all require a proper thermal treatment for the SnO 2 ETLs. Herein we present a simple method to synthesize SnO 2 nanoparticles (NPs) at room temperature. By using butyl acetate as a precipitator and a proper UV-Ozone treatment to remove Cl residuals, excellent SnO 2 ETLs were obtained without any thermal annealing. The highest power conversion efficiency (PCE) of the prepared PSCs was 19.22% for reverse scan (RS) and 18.79% for forward scan (FS). Furthermore, flexible PSCs were fabricated with high PCEs of 15.27%/14.74% (RS/FS). The low energy consuming SnO 2 ETLs therefore show great promise for the flexible PSCs' commercialization.