Back Interface Passivation for Efficient Low‐Bandgap Perovskite Solar Cells and Photodetectors

Abstract

Low‐bandgap (Eg~1.25 eV) mixed tin‐lead (Sn‐Pb) perovskites are promising candidates for efficient solar cells and self‐powered photodetectors; however, they suffer from huge amounts of defects due to the unintentional p‐type self‐doping. In this work, the synergistic effects of maltol and phenyl‐C61‐butyric acid methyl ester (PCBM) were achieved to improve the performance of low‐bandgap perovskite solar cells (PSCs) and unbiased perovskite photodetectors (PPDs) by pas-sivating the defects and tuning charge transfer dynamics. Maltol eliminated the Sn‐related traps in perovskite films through a strong metal chelating effect, whereas PCBM elevated the built‐in electric potential and thus improved voltage through the spike energy alignment. Combining both ad-vantages of maltol and PCBM, high‐quality perovskite films were obtained, enabling low‐bandgap PSCs with the best efficiency of 20.62%. Moreover, the optimized PSCs were further applied as self-powered PPDs in a visible light communication system with a response time of 0.736 μs, presenting a satisfactory audio transmission capability.