Graphene quantum dot-enhanced band alignment in ZnO/CuO heterojunctions for self-powered UV photodetection

Abstract

ZnO-based heterostructures hold promise for ultraviolet (UV) photodetection due to their tunable optoelectronic properties, yet face challenges in achieving high responsivity and low-cost fabrication simultaneously. In this study, a graphene quantum dots (GQDs)-sensitized n-ZnO/p-CuO heterojunction is fabricated via a facile spin-coating method. GQD sensitization stimulates charge carriers in ZnO and CuO and allows energy band alignment to be realized by a spontaneous time-correlated transient response. The ZnO/GQD/CuO device exhibits self-powered operation (0 V bias) under 365 nm illumination with a remarkable specific detectivity of 5 × 109 Jones and fast response times (rise: 21 ms, decay: 30 ms). First-principles calculations reveal that GQDs enhance carrier separation efficiency by reducing the ZnO/CuO interface barrier. This work not only proposes an effective way for heterojunction optimization through quantum dot mediation but also provides a new approach for high-performance self-powered UV detectors.