Photocombustion-Processed Nanocrystalline Tin Oxide for Highly Reproducible and Efficient Perovskite Solar Cells

Tin oxide (SnO 2 ) is widely recognized as a suitable n -type semiconductor for various electronic devices, including solar cells, light-emitting diodes, gas sensors, and transistors. In particular, SnO 2 electron-transport layers (ETLs) play a crucial role in achieving high power conversion efficiencies (PCEs) in perovskite solar cells (PSCs). However, solution-processed SnO 2 ETLs often suffer from several shortcomings, such as poor film morphologies (e.g., pinholes and roughness), low crystallinity, and insufficient conductivity. As such, efficient approaches are required for designing high-quality SnO 2 ETLs by combining physical and chemical protocols. In this study, a photocombustion process involving irradiation with intense ultraviolet light was employed. The process generated a substantial amount of heat, facilitating rapid disproportionation and dehydration reactions of the radicals. The tin precursor thin films were transformed into 20 nm-thick-nanocrystalline SnO 2 ETLs. After 2 h, the SnO 2 ETLs exhibited high film uniformity and fast electron extraction and transfer at their interfaces with the perovskite layer. The PSCs reached the PCE of 20.66% and effectively suppressed hysteresis. Furthermore, excellent stability was demonstrated as the unencapsulated device exhibited a PCE retention of 87.4% under 1 sun illumination for 1000 h.