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

Abstract

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 (Cu:V₂O₅). 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 Förster 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 Förster 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 ∼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.