Low-temperature sintered SnO2 electron transport layer for efficient planar perovskite solar cells

Lead amine halide perovskite solar cells (PSCs) have become dominant photovoltaic research topic in this decade. Electron transport layer (ETL) play a crucial role on PSCs. Here, we use tin tetrachloride as Sn source to synthesize SnO 2 nanocrystals in a simple hydrothermal method. The as-synthesized SnO 2 is spin-coated on FTO substrate, and then sintered under low temperature to form the ETL of planar PSCs. The concentration of SnO 2 spin-coating solution and sintering temperature have great influence on the ETL quality and charge transportation in PSCs. Through optimized treatment (0.15 M SnO 2 , 120 °C sintering), the high quality SnO 2 ETL with a uniform coverage, appropriate thickness, less charge recombination and low resistance can be obtained. Based on the ETL, a planar PSC with FA x MA 1−x PbI 3 achieves a high power conversion efficiency (PCE) of 19.34%. In addition, the planar PSCs based on SnO 2 exhibit a stable PCE output and slight hysteresis. These researches provide a low-cost, easy strategy to fabricate tin oxide, and present potential to replace traditional titanium oxide (TiO 2 ) in PSCs in the future.