Effect of Gamma-Ray Irradiation of Amorphous SnO2 Electron Selective Layers on the Properties of Ambient-Air Synthesized Planar Perovskite Solar Cells

The effect of low-dose gamma-ray irradiation on an amorphous SnO₂ electron-selective layer (ESL) was investigated in this study. Further, its impact on the photovoltaic (PV) performance of planar perovskite solar cells (PSCs) based on MAPbI₃ and CsFAMAPbIBr absorber layers has been evaluated for the first time. The properties of the SnO₂ layer were substantially modified by the gamma-ray irradiation of regulatory exemption radioactive sources (Co-60). Gamma-ray irradiation promoted the formation of large perovskite grains by creating a hydrophilic surface via the generation of ─OH on the amorphous SnO₂ film surface. In addition, gamma-ray irradiation increased the conductivity of the SnO₂ layer due to the generation of the proper oxygen vacancies in SnO₂. From the optimization of gamma-ray irradiation parameters, we achieved a best efficiency of 18.03% using the MAPbI₃ perovskite film owing to the enhanced perovskite densification and increased SnO₂ conductivity. This efficiency was significantly improved compared to that (16.03%) of a pristine device. In addition, a power conversion efficiency (PCE) of 20.01% was achieved using the CsFAMAPbIBr mixed perovskite film and the gamma-ray irradiated SnO₂. The results suggest that systematic low-dose gamma irradiation treatment of ESLs has a synergistic effect of controlling surface properties, enhancing perovskite crystal growth, and controlling oxygen vacancies, and is relatively simple and has high potential as a surface treatment process.