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

Tin oxide (SnO2) 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, SnO2 electron-transport layers (ETLs) play a crucial role in achieving high power conversion efficiencies (PCEs) in perovskite solar cells (PSCs). However, solution-processed SnO2 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 SnO2 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 SnO2 ETLs. After 2 h, the SnO2 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.