The performance improvement of CuO/TiO2 heterojunctions was investigated to contribute to the understanding of factors influencing the performance of the heterojunctions and their potential applications in sunlight-driven photodetectors and photocatalysts. By using optimal parameters (TiO2 (CuO)'s thickness of 5 µm (60 nm), acceptor (donor) doping concentration of 1017 cm−3 (1018 cm−3), required interface defect of 1013 cm−3, and under AM 1.5G illumination at 27 °C and 0 V bias voltage, the device achieved a photocurrent density of 13 mA/cm2, a photoresponsivity of 3.25 A/W, a detectivity of 1.8 × 1014 Jones, and effectiveness across UVA and visible light. At temperatures approaching 300 °C, the CuO/TiO2 device maintained its high photoresponsivity and efficiency, indicating its suitability for applications in high-temperature environments, such as hydrogen production through photocatalysis. The results suggest that the devices have the potential to be utilized in sunlight-driven optoelectronic and photocatalyst industries, offering cost-effectiveness and high efficiency. [ABSTRACT FROM AUTHOR]