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The 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.