Vertically aligned and ordered ZnO/CdS nanowire arrays for self-powered UV–visible photosensing

Abstract

Photodetectors based on photoconductivity effect are usually driven by an external power source. A self-powered photodetector can be powered by incident light using the photovoltaic effect. Here, photoelectrochemical cells with periodically aligned ZnO/CdS nanowire arrays as photoanodes were fabricated and investigated for detecting UV and visible light. At zero bias, this self-powered UV–visible photodetector showed high responsivities of 35.4 and 23.2 mA/W for UV and visible light, a fast rise time of 0.18 s, and a decay time of 0.32 s. The spectral responses of the self-powered photodetectors based on ZnO/CdS nanowire arrays exhibited superior photoresponse in both UV and visible regions in comparison with ZnO nanowire film and ZnO nanowire arrays. The high photosensing performance originates from the excellent light trapping ability at broadband wavelengths and the high charge collection efficiency of the highly ordered ZnO/CdS nanowire arrays. The results indicate that the ZnO/CdS heterojunctions with periodic nanostructures provide a facile frame for UV–visible detecting applications.