Improved sensitivity in self-powered photoelectrochemical UV photodetector by application of graphene quantum dots

Here, we demonstrate the successful application of graphene quantum dots (GQDs) as a sensitizing material in a self-powered photoelectrochemical (PEC) UV photodetector (PD). Relative enhancements greater than 40% in photocurrent were achieved by the application of a GQDs sensitized TiO2 layer as the photoanode in the self-powered PEC UV PD, attaining 118 mA W-1 responsivity compared to 83 mA W-1 responsivity of PD made by pure TiO2 photoanode under the illumination of 365 nm UV light. The GQDs improved both the light-harvesting efficiency and the charge collection efficiency in the PEC PD by increasing the UV light absorption and hindering the recombination at the photoanode/electrolyte interface. The UV PD based on the GQDs sensitized TiO2 layer exhibits a high photoresponse sensitivity of 786,880% at a low light intensity of 2 mW cm(-2), a rise time of 0.12 s, and a decay time of 0.03 s without any external bias. This study shows that sensitization of photoanode layer with a proper sensitizing material such as GQDs with large absorption coefficient in UV wavelength region can be a facile strategy to improve the responsivity and sensitivity of low-cost, environmentally friendly, and easy-manufacturing self-powered PEC UV PDs.