In this study, we investigated the effect of different reducing agents (ascorbic acid and sodium boron hydride) on optoelectronic properties of TiO2:Cu2O nanocomposites. The TiO2:Cu2O nanocomposites were characterized using X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Energy dispersive X-ray (EDX). The electronic properties of the structure were calculated with the density functional theory (DFT). Both devices showed good responsivity and detectivity against light intensities. The photosensitivity of the devices had linear increasing profile with increasing light power. It is noteworthy that both devices demonstrated well-rectifying behaviors as a result of having low reverse bias and greater forward bias currents at the I–V characteristics in low light. The reduction of the band gap shifted the absorption band gap from the visible light region to the red edge. Density Functional Theory (DFT) calculations which has been done by using CASTEP are in good agreement with our experimental results. Ti(1 − x)CuxO2 (7.5:1) band gap is 1.18 eV which is compared to the Shockley ve Quiser (SQ) limit. Ti(1 − x)CuxO2 (15:1) band gap is 1.83 eV while the band gap is 2.28 eV for stoichiometric TiO2 with our DFT calculations. Thus, the band gap narrowed with increasing Cu amount. This provides an improvement in light absorption. In conclusion, the results demonstrate that Al/TiO2:Cu2O/p-Si can be used in optoelectronic applications.