Influence of the annealing temperature on the self-powered CuO/ZnO NRs heterojunction photodetector

In this study, the fabrication and comprehensive analysis of CuO/ZnO nanorod (NR) heterojunction photodetectors were carried out, focusing on the influence of annealing temperatures (400 degrees C, 500 degrees C, and 600 degrees C) on their structural, optical, and electrical characteristics. The ZnO nanorods were synthesized via a hydrothermal method, followed by a spin-coating deposition of CuO thin films. The resultant heterojunctions were subjected to different annealing treatments to determine the optimal conditions for enhanced photodetector performance. Characterization techniques such as Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive x-ray Spectroscopy (EDX), x-ray Diffraction (XRD), and UV-vis spectroscopy were employed to assess the quality and composition of the heterostructures. The analyses revealed a polycrystalline structure with monoclinic phases for CuO and wurtzite phases for ZnO. Photodetectors annealed at 400 degrees C exhibited the highest performance metrics, achieving a photoresponse ratio (Iph/Idark) of 26.3, photosensitivity (Sph%) of 2531.6, and a specific detectivity (D*) of 4.58 x 1010 Jones under 405 nm UV light illumination. These devices also demonstrated rapid response times of 0.8 s without any external bias, indicating effective exciton separation and charge transport facilitated by the built-in electric field at the heterojunction interface. The study underscores the critical role of annealing temperature in optimizing the photodetector properties of CuO/ZnO NRs, positioning these self-powered devices as promising candidates for future ultraviolet sensor applications in optoelectronics.