The improved photoresponse properties of self-powered NiO/ZnO heterojunction arrays UV photodetectors with designed tunable Fermi level of ZnO

Self-powered ultraviolet (UV) photodetectors (PDs) based on ZnO heterojunctions have attracted more attention due to the simple preparation and excellent photoresponse performance without any power supply. The self-powered UV PDs based on NiO nanoflakes/ZnO nanorod arrays (NRs) heterojunctions were fabricated by a low-cost, simple chemical bath deposition (CBD) method. The crystal quality, optical and electronic properties of ZnO NRs is modified by Al3+ ions additions in the precursor solution. The heterojunction devices with ZnO NRs grown in 0.5% Al3+ ions additions precursor solution exhibit a narrow UV spectral selectivity, high photoresponsivity R (85.12 mA/W) and detectivity D* (1.74 × 1012 cm·Hz1/2/W) and a fast response speed (~2 ms) under 378 nm UV light for low intensity irradiance (0.2 mW/cm2) at zero bias. The large built-in electric field of the NiO/ZnO heterojunction with the increased Fermi level of ZnO NRs provide a strong driving force to separate and transfer the photo-generated carriers, decrease the recombination of the carriers and then improve the photoresponse performance of heterojunction devices without external bias.