Photo‐generated Charge Trapping in Phase Segregated Halide Perovskites – A Comprehensive Approach towards Efficient Photo‐Rechargeable Ion Capacitors

Abstract

AbstractThe right balance between photo‐absorption and electronic‐ionic conductivity is needed for photo‐rechargeable bifunctional devices for off‐grid energy applications. Recently halide perovskites have been utilized for photo‐rechargeable supercapacitors, but the mechanism of photo‐capacitance enhancement is not known. Herein, we have fabricated mixed halide perovskites‐based photo‐rechargeable supercapacitors in two ways and examined the energy harvesting and storage capabilities of these devices. The porous electrode prepared from the mixed halide perovskites (CH3NH3PbBr2I) shows photo‐capacitance enhancement up to 15 F/g, while the electrode prepared from the blend of CH3NH3PbBr3 and CH3NH3PbI3 (2 : 1 by molar ratio) shows the photo‐capacitance diminution up to 12 F/g. Despite higher specific capacitance (~38 F/g in dark) in blend perovskites due to increased ion diffusion, the photo‐generated charge trapping at nanoscale phase segregation is responsible for the diminution in photo‐capacitance of these bifunctional devices, while a uniform mixing of halide ions in mixed halide perovskites nanocrystals leads to increased photo‐capacitance.