This paper presents the impact of thickness of RF sputtered CdTe thin film as an absorber layer through structural and optical characterization in ZnxCd1-xS/CdTe solar cells at lower concentration of zinc (Zn). The crystallographic, morphological and optical properties of CdTe thin film fabricated on top of bare soda-lime glass were elucidated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and ultraviolet (UV) spectrophotometer. XRD spectra shows that crystallinity increases in thicker samples and the CdTe (1 1 1) diffraction peak intensity centered at 23.825 degrees increases with the increase of film thickness confirming the zinc blend structure of CdTe thin film. The window layer ZnxCd1-xS was fabricated with optimum deposition conditions by co-sputtering of ZnS and CdS. The complete cell was fabricated by RF magnetron sputtering with the cell configuration of glass/FTO/ZnxCd1-xS/ZnTe/Ag. With the increasing thicknesses of CdTe the cell efficiency increases with the highest efficiency of 8.79% for 3.5 mu m of CdTe. This paves the way of novel window of ZnCdTe for smoothening the junction mismatches in hetero-junction CdTe thin film solar cells.