Efficient UV-visible Photodetector Based on Single CuO/Cu2O Core-shell Nanowire

One-dimensional nanostructures such as nanowires show better photoresponse than that of their bulk counterparts because of unidirectional transport that significantly reduces recombination and scattering of photo-generated charge carriers. CuO and Cu2O are relatively abundant transition metal oxides with optical band gaps suitable for efficient detection of UV and visible radiation. In addition, they form type-II heterojunction for efficient charge separation. Here, we report the fabrication of CuO/Cu2O core-shell nanowire arrays by chemical bath deposited Cu2O layer over thermally grown CuO nanowires. Photodetector devices based on individual CuO and CuO/Cu2O core-shell nanowire are fabricated through photolithography using Pd metal contact for studying response under UV and visible light illumination. Core-shell nanostructures show better performance in terms of responsivity, detectivity, external quantum efficiency, faster response, and recovery times over that of bare CuO nanowires. This is attributed to the Ohmic junction formed at the Pd-Cu2O interface that ensures barrierless hole transport for the core-shell photodetector. Further, the type-II heterojunction formed at CuO/Cu2O interface enhances hole concentration in the Cu2O shell layer, which is responsible for better photoresponse in core-shell nanostructures. The results establish that CuO/Cu2O core-shell nanowires offer simplified design and highly efficient photodetectors that can be used in several optoelectronic devices.