High-performance self-powered ultraviolet photodetector based on CuI/MgZnO heterojunction with interfacial engineering by Cu2O

A novel self-powered ultraviolet (UV) photodetector (PD) based on a CuI/MgZnO heterojunction modified by an ultrathin Cu₂O layer has been fabricated by the successive ionic layer adsorption and reaction (SILAR) method. Compared with the CuI/MgZnO self-powered PD, the optimised heterojunction PD (CuI/Cu₂O/MgZnO) exhibits significantly improved self-powered properties. Under 325 nm UV light at an intensity of 450 µW/cm², the CuI/Cu₂O/MgZnO heterojunction PD shows exceptional photoelectric performance, featuring a high photo-to-dark current ratio of 1611, a large responsivity of 48.43 mA/W, and rapid rise and decay times of 261 ms and 890 ms, respectively, without any external power supply. Incorporating the Cu₂O interface layer results in notable enhancements in responsivity and detectivity compared to the heterojunction without the Cu₂O layer. This improvement is attributed to heterojunction interface contact, energy band engineering, and the tunneling effect. The Cu₂O layer expands the depletion zone and promotes charge separation. Due to its thinness, charges can tunnel through the Cu₂O layer from one metal electrode to another. Furthermore, the interfacial Cu₂O layer can alter the valence band offset and the conduction band offset of the p-CuI/n-MgZnO junction, enhancing carrier transport between MgZnO and CuI. These results lay the groundwork for using self-powered MgZnO-based heterojunction photodetectors in light-based devices in the future. They also demonstrate the potential of designing novel heterojunctions to create high-performance self-powered PDs for UV detection.