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 SnO₂ nanocrystals in a simple hydrothermal method. The as-synthesized SnO₂ is spin-coated on FTO substrate, and then sintered under low temperature to form the ETL of planar PSCs. The concentration of SnO₂ spin-coating solution and sintering temperature have great influence on the ETL quality and charge transportation in PSCs. Through optimized treatment (0.15 M SnO₂, 120 °C sintering), the high quality SnO₂ 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_xMA_1−xPbI₃ achieves a high power conversion efficiency (PCE) of 19.34%. In addition, the planar PSCs based on SnO₂ 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 (TiO₂) in PSCs in the future.