Conventional rare and toxic materials still dominate the photodetector industry. Therefore, efficient photodetectors based on environmentally friendly and low-cost materials are a high priority area. Addressing this issue, an n-Cu2O/p-CuI heterojunction based photodetector was fabricated and characterised. The photodetector was synthesised via atmospheric pressure hydrothermal and drop cast deposition processes. The Cu2O/CuI heterojunction was structurally, morphologically and optically characterised using XRD, EDX, SEM, and UV – VIS, respectively. At zero bias, the photodetectors exhibited a high sensitivity of 2.355 × 105 and 7 × 103 for visible and UV light, respectively. The observed highest responsivity at 465 nm is 250 mA W−1. Further, the device showed a 2 nA cm-2 dark current with a fast rising and falling time of 582 and 817 μs, respectively. The long term ageing study showed that photodetector has a lifetime of more than four years. These results reveal that n-Cu2O/p-CuI photodetector is a favourable approach for affordable, environmentally friendly and high-performance UV/Visible photoelectronic applications.