Transparent ZnO/CuI nanoparticle heterojunction for self-powered UV detection: Fast response and high Voc with CuO interfacial layer

Abstract

The allure of cost-effectiveness, scalability, and flexibility makes solution-processed transparent thin films appealing for applications like smart windows, displays, portable electronics, and automotive systems. The present study investigates the development of a transparent ZnO/CuI heterojunction for self-powered UV photodetection with all nanoparticle layers made using a simple, non-toxic solution-processed method. Although the choice of all nanoparticle layers makes the device much simpler and scalable, the prime challenges such as the high potential barrier for carrier transport, and recombination-tunneling paths due to interface defects undermine its functionality. To mitigate these issues and to enhance the charge transport, CuO is introduced as a novel interfacial layer carefully chosen for the energy band alignment within the heterojunction. This significantly improves the responsivity to 20.83 mA/W and detectivity to 1.61 × 10¹², in the self-powered mode with a Voc of 41 mV under 5 mW/cm² UV illumination (365 nm). Interestingly, the device exhibits a faster response, with the rise and decay time of 0.025 s and 0.106 s respectively, surpassing other solution processed ZnO/CuI heterojunction devices reported. The photodetector demonstrates efficient performance under low-intensity UV illumination (∼0.056 mW/cm²), as confirmed by intensity-dependent studies. This presents a low-cost scalable approach for energy efficient weak light UV photodetectors with transparent heterojunction films potentially useful in future smart electronics and window applications.