α-Ga2O3 Nanorod Array–Cu2O Microsphere p–n Junctions for Self-Powered Spectrum-Distinguishable Photodetectors

Most of the photodetectors can measure all of the light illumination with a wavelength below the absorption edge of the detector materials, while they cannot distinguish the different waveband. Herein, a self-powered spectrum-distinguishable photoelectrochemical (PEC) type photodetector based on an α-Ga2O3 nanorod array (NA)/Cu2O microsphere (MS) p–n junction was reported. Under the combined action of the built-in electric field of the p–n junction and the semiconductor/electrolyte junction, the photodetector exhibits an opposite direction of the photocurrent to the illumination of 254 and 365 nm UV light under the applied bias of 0 V, which can be used to distinguish the different wavelengths of light. The photodetector shows a responsivity of 0.42 mA/W under 254 nm UV light and 0.57 mA/W upon 365 nm, respectively. Our results provide an idea for distinguishing the different illumination wavebands through a photodetector constructed by the heterojunction with two different band gap materials.