A F?rster resonance energy transfer enabled photo-rechargeable battery with an energetically misaligned Cu-porphyrin dye/Cu:V₂O₅ photocathode

This study introduces a novel photo-rechargeable battery featuring a photocathode that comprises TiO2 co-sensitized with copper tetraphenylporphyrin (CuTPP) dye and copper-doped vanadium pentoxide (CuV2O5 ). In an unbiased mode under illumination, this architecture facilitates charging up to 1.4 V, delivering a photocharging capacity of 91 mA h g(-1), a feat made possible by Forster Resonance Energy Transfer (FRET) from Cu:V2O5 to CuTPP dye. The energy level mismatch inherent in these materials restricts direct photo-excited charge injection but enables a highly proficient energy transfer, accomplishing a FRET efficiency of 29.2%, attained at a Forster distance of 3.3 nm. This process yields a photocharging capacity of 268 mA h g(-1) under 1 sun irradiance, a significant enhancement from 210 mA h g(-1) capacity in the dark, both determined at 100 mA g(-1). The V2O5 analogue of this photo-battery exhibits a reduced performance owing to lower electrical conductivity and inefficient charge separation. Both V2O5 and Cu:V2O5 -based photo-batteries demonstrate respectable overall photoconversion and storage efficiencies, recording 3.9% and 3.3% respectively. The TiO2/CuTPP/Cu:V2O5 /Zn2+/Zn flakes-activated carbon/Ni photo-battery shows promising longevity as it maintains similar to 100% of its initial capacity in light, indicating a commendable cycling stability. This investigation proposes a paradigm shift for photo-battery development by obviating the necessity for energy-level-aligned photocathodes.