Photodiodes have gained great attention for lightning control and optical communication over the last two decades. To obtain faster and more sensitive photodiodes are important for industrial applications. In this study, atomic layer deposition (ALD) technique was used to fabricate ZnO interlayer on p-Si, and thermal evaporation technique was employed to deposit Ag rectifying and Al ohmic contacts on ZnO and back surface of p-Si, respectively. The UV–Vis spectrometer was used to characterize optical behaviors of the ZnO interlayer. I-V measurements were conducted to characterize of Ag/ZnO/p-Si heterostructure for various solar light power intensities of dark, 20, 40, 60, 80 and 100 mW cm−2 and at various wavelengths from 351 nm to 800 nm by 50 nm intervals. According to I-V characteristics, the device exhibited increasing current at reverse biases depending on increasing light power intensity, and this confirmed photodiode behavior. Various diode parameters such as rectifying ratio, threshold voltage, series resistance, barrier height, etc. were determined and discussed in details from forward bias characteristics to investigate diode characteristics of the Ag/ZnO/p-Si heterostructure. The photodetection parameters such as responsivity, specific detectivity and external quantum efficiency (EQE) also were investigated. The Ag/ZnO/p-Si heterostructure exhibits good photodetection performance at all visible range of electromagnetic spectrum and can be good candidate for optoelectronic applications.