From UV to Vis Broadband Photodetectors Based on ZnO/CuO/NiO Core–Shell–Shell Heterojunction Nanostructures

In recent years, with the development of wearable electronics, the demands for high-performance photodetectors with smaller size, lower power consumption, and higher sensitivity have increased remarkably. Photodetectors based on one-dimensional (1D) zinc oxide (ZnO) nanowires (NWs) have been intensively investigated owing to their geometrical nanostructure possessing a large surface-to-volume ratio, high carrier mobility, and adjustable optical absorption. However, ZnO NW photodetectors usually can only detect ultraviolet (UV) light, limiting their application in the field of photodetection. In this paper, a heterojunction photodetector (HPD) based on ZnO/CuO/NiO (ZCN) core–shell–shell NWs is reported. The nanoscale copper oxide (CuO) film is deposited on hydrothermally grown ZnO NWs as the visible light absorber. The nanoscale nickel oxide (NiO) shell layer is uniformly coated on the surface of ZnO/CuO NWs by spin coating, which improves the detection capability of the photodetector in the range of UV-to-visible (UV–vis) significantly. Benefited from the large light absorption area provided by the 1D nanostructure and the type II band alignment, the ZCN NW HPD shows a fast response (rise/decay 0.12/0.22 s) and a large sensitivity of 18.65 mA/W under UV irradiation at a 0 V bias. Experimental and simulation results show the key role of NiO shell layer in ZCN NW HPD. Our results suggest core–shell–shell heterojunction nanostructures to develop high-performance photodetectors for next-generation UV–vis broadband photosensing applications.