Multi-cell quasi-solid-state photo-supercapacitor integrating ZnO, ZnO/g-C₃N₄, and MnO₂ for simultaneous light harvesting and energy storage

Solar energy intermittency requires compact devices for simultaneous photon-to-charge conversion and storage. Conventional photo-supercapacitors (PSCs) are limited by poor UV response in MnO₂-based systems, restricted visible-light absorption of wide-bandgap oxides, and charge recombination in tandem electrodes. This study addresses these challenges through a multi-cell quasi-solid-state PSC that integrates separate ZnO, ZnO/g-C₃N₄, and MnO₂ cells, enabling efficient UV and sunlight harvesting while avoiding recombination losses. The optimized device delivered a specific capacitance of 32.56 F g -1 , Coulombic efficiency of 81.86%, power density of 9375 W kg -1, and energy density of 18.09 Wh kg -1 under illumination. It powered a red LED for 75 s after bias charging and operated a digital clock for 30 min when charged under direct sunlight, demonstrating strong potential for autonomous solar energy systems.