Transparent conducting Copper oxide CuO thin films were successfully synthesized on glass and n-type Silicon substrates by successive ionic layer adsorption and reaction method. The crystal structure, surface texture, optical and electrical properties were studied. The results revealed that the deposited CuO thin films at different cycles number (5, 10, 15), have polycrystalline structure nature with monoclinic phase, and the crystallite size increases with the increase of cycles number. The average roughness and the root mean square values increase with increasing cycles number. The optical energy band gap and Urbach energy was decrement from 2.33 eV and 1.2 eV for 5 cycles to 2.1 eV and 0.82 eV for 15 cycles. The electrical properties of Ni/CuO/n–Si pn junction were studied using current–voltage (I–V) measurements. The barrier heights 