This paper reports the growth of n-type CuO (copper II oxide) thin film with improved crystallinity on p-Si substrate using sol-gel spin coating process. The electrical conductivity of the deposited film was determined as n-type using Hot point probe measurement. Further, an in-depth analysis of the annealing time effect on the deposited thin film was done to observe its structural and optical properties. The structural characterization of the deposited film was done with the help of X-ray diffraction and Field Emission Scanning electron microscope. The optical parameters, such as reflectance, refractive index were determined in the spectral range of 300 nm 800 nm with the help of ellipsometry. The effects of annealing time on band gap, extinction coefficient, dielectric constant for the annealed films were also extracted to observe its application for optoelectronic devices. Further, using the film annealed for 15 mins. n-CuO/p-Si hetero-junction diode was fabricated and characterized. The experimentally obtained electrical parameters of the fabricated n-CuO/p-Si hetero-junction diode were also validated by the results of numerical simulation data obtained by usinga commercially available device simulator. The developed hetero-junction was investigated by considering a conventional thermionic model. It showed high rectification ratio equal to 6805 and a barrier height equal to 0.81 eV.