Ultraviolet/Visible Photodetectors Based on p–n NiO/ZnO Nanowires Decorated with Pd Nanoparticles

Chemical solutions consisting of NiO/ZnO p–n heterojunction nanowires (NWs) decorated with Pd nanoparticles on a glass substrate were used to fabricate an ultraviolet (UV)/visible photodetector. The photodetector was composed of ZnO hexagonal wurtzite and NiO cubic crystalline structures. A few NiO nanograins were found to epitaxially grow on the ZnO NW surface. The current–voltage curve for the photodetector exhibited rectification in the dark and under green and blue light-emitting diode (LED) illumination, whereas an approximately linear current–voltage curve was found under UV LED illumination. The I green / I dark, I blue / I dark, and I UV / I dark ratios for the photodetector were 91.4, 403.2, and 1.25 × 10 5, respectively. Multilayer structures of the photodetector are sensitive toward the UV and visible bands.