Photoelectrodes based on selenium-polypyrrole-vanadium pentoxide nanowire films for high-performance lightweight symmetric photo-supercapacitors: A flexible photo-rechargeable electrical energy storage device

V2O5-PPy, Se-V2O5, and Se-V2O5-PPy films on flexible indium tin oxide electrodes have been used to prepare flexible, lightweight and high-performance flexible photo-supercapacitors. Vanadium pentoxide (V2O5) nanowires, which are excellent electrode compounds for high electrochemical performance and long cycle life photoresponsive supercapacitance, have been synthesized and their photo-assisted supercapacitor performances have been enhanced by selenium and polypyrrole (PPy). The capacitive performances of Se-V2O5-PPy have been improved to 375 mF/cm2 at 0.25 mA.cm−2, which is over 2.1 times that of pure V2O5, 1.5 times those of the corresponding values for V2O5-PPy, 1.6 times of Se-V2O5 and 1.7 times of Se-PPy at identical current densities. Areal capacitance values of 151 mF/cm2 and 375 mF/cm2 (@ 0.25 mA/cm2) have been shown by Se-V2O5-PPy electrodes prepared in the dark and under light irradiation, respectively. Good cycle stability of 91% is shown by the assembled device after 10,000 cycles and its voltage window can be increased to 2.0 V. Furthermore, maximum volumetric energy densities of 16.8 and 41.6 Wh/kg can be obtained in the dark and under light irradiation, respectively. The flexible self-powered photo-supercapacitors show remarkable flexibility while maintaining their supercapacitor performance well even under various bent conditions, which signifies the outstanding flexibility of this device.