Researchers from Clemson University and the Indian Institute of Science have designed a smart supercapacitor using a novel stack of metal oxides — vanadium pentoxide and zinc oxide — that can efficiently harvest energy from sunlight and simultaneously store it in a self-chargeable device.

Widely used in charge transfer applications, the performance of zinc oxide as a photoactive material was improved by stacking the material with vanadium pentoxide on fluorine-doped tin oxide (FTO) glass. The resulting heterostructure displayed improved separation of photogenerated charge carriers and enhanced light absorption range.

Schematic diagram of charge storage mechanism under (a) dark and (b) UV-illuminated conditions. (c) Band diagram showing the flow of photogenerated electrons under UV illumination. Source: J. Mater. Chem. A, 2023, 11, 95-107

When tested as photo-responsive electrode material in an optically chargeable supercapacitor, the researchers documented 178% enhancement in capacitance at 0.2 μA cm⁻² current density under ultraviolet (UV) illumination. The unique combination of zinc oxide and vanadium pentoxide bandgaps and the FTO substrate (bandgap ∼3.6 eV) yields an ideal electrode for both charge generation and storage.

The research published in RSC Journal of Materials Chemistry A confirms that the device showed excellent electrochemical performance and stability for over 5,000 cycles.