Metal Ion-Incorporated Lead-Free Perovskites toward Broadband Photodetectors

Metal halide perovskites have excited tremendous research interests due to their extraordinary photovoltaic and optoelectronic performance. Cs2SnI6 has emerged as a promising lead-free perovskite in advanced optoelectronics due to its high stability, appropriate bandgap, and high absorption coefficient. The performance of two-dimensional (2D) Cs2SnI6-based photodetectors is limited as compared to lead-based perovskites. Here, we report a simple strategy for incorporating aliovalent metal ions (nickel and zinc) for doping or passivation of perovskites to improve their performance. Aliovalent metal ions are employed to break the inherent dark transition of the 2D Cs2SnI6, greatly increasing photoluminescence by two orders of magnitude than pristine Cs2SnI6. Density function calculation reveals the n-type doping of nickel ions without introducing any deep trap states. We further demonstrate that the surface passivation of 2D Cs2SnI6 by zinc ions can greatly reduce surface trap/defect density. Aliovalent metal ion-incorporated Cs2SnI6 perovskites exhibit broadband detection, high responsivity (1.6 × 103 A W–1, for Ni-incorporated Cs2SnI6) and high detectivity (1.56 × 1013 Jones, for Zn-incorporated Cs2SnI6). These results will prompt research on the influence of metal ions in perovskite materials that may afford novel properties for next-generation optoelectronics.