The indium tin oxide (ITO) film was treated with 100 W-power hydrogen plasma for 5 min before being used as a substrate to fabricate thermally evaporated CdS thin films. The structural, optical, and electrical properties of ITO and grown CdS films affected by pre-deposition plasma treatment were studied. SEM images show that the surface of ITO film becomes smoother after treatment. AFM analysis determines a decrease and increase in the surface roughness of ITO and CdS thin films after treating the ITO substrate. The XRD patterns show an improvement in the crystallinity of the fabricated thin films. Increasing the optical energy bandgap up to 3.699 eV and.2.481 eV for ITO and deposited CdS films respectively. So, design simple CdS/CdTe solar cells at a device temperature of 300 K. Enhancing the photovoltaic parameters and an increment of about 20 % in solar cell performance.