PACS 78.66.Hf, 81.05.Dz, 81.15.Lm, 84.60.Jt Composition, optical properties, structure properties, and surface morphology of thin films of Cd 1-x Zn x S (x ≤ 10%) prepared by chemical bath deposition (CBD) are reported. The best cell efficiency was 15.7%. It used a Cd 1-x Zn x S window layer, was confirmed by NREL (V oc = 840.1 mV, J sc = 24.81 mA/cm 2 , and FF = 75.55%), and had a CTO/ZTO/Cd 0.92 Zn 0.08 S/CdTe cell structure. The use of low zinc concentration in the Cd 1-x Zn x S layer and interdiffusion between Cd 1-x Zn x S and CdTe layers were assumed to be the reasons for maintaining high V oc and FF.