This paper presents ultrafast response, self-powered UV photodetectors (PDs) based on ZnO/SiO 2 /Si heterojunction diodes, utilizing zinc oxide (ZnO) nanorods as the photosensitive layer. This configuration results in photodetectors exhibiting unprecedentedly rapid response times, with rise and decay times reduced to 440 ns and 320 ns, respectively. Our study, focusing on ZnO nanorod PDs, not only demonstrates ultrafast response times but also highlights the role of hydrothermal synthesis temperature in tuning the devices’ performance. These findings represent a significant leap forward in the development of high-performance, self-powered UV PDs. The effects of different hydrothermal temperature on the morphology, crystal structure, and optoelectrical properties were systematically investigated using various characterization techniques, including field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) analysis, photoluminescence analysis, and current-voltage ( I-V ) measurements.