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 geometricalnanostructure possessing a large surface-to-volume ratio, high carriermobility, and adjustable optical absorption. However, ZnO NW photodetectorsusually can only detect ultraviolet (UV) light, limiting their applicationin the field of photodetection. In this paper, a heterojunction photodetector(HPD) based on ZnO/CuO/NiO (ZCN) core-shell-shell NWsis reported. The nanoscale copper oxide (CuO) film is deposited onhydrothermally grown ZnO NWs as the visible light absorber. The nanoscalenickel oxide (NiO) shell layer is uniformly coated on the surfaceof ZnO/CuO NWs by spin coating, which improves the detection capabilityof the photodetector in the range of UV-to-visible (UV-vis)significantly. Benefited from the large light absorption area providedby the 1D nanostructure and the type II band alignment, the ZCN NWHPD shows a fast response (rise/decay 0.12/0.22 s) and a large sensitivityof 18.65 mA/W under UV irradiation at a 0 V bias. Experimental andsimulation results show the key role of NiO shell layer in ZCN NWHPD. Our results suggest core-shell-shell heterojunctionnanostructures to develop high-performance photodetectors for next-generationUV-vis broadband photosensing applications.