Transparent conducting oxides (TCO), such as indium tin oxide (ITO), fluorine doped tin oxide (FTO), and Al doped zinc oxide (ZnO), have been used as transparent electrodes in CdTe/CdS thin film solar cells. The merits of different TCOs and the properties of the CdTe/CdS solar cells in superstrate configuration have been investigated. The average transmission of CdS/FTO is 80% while CdS/ZnO window layers have a lower transmission of 40 to 60%. Effects of CdCl2 treatment on the recrystallization of CdTe have been studied with XRD and SEM. A large increase in the grain size along with the loss of the (111) preferred orientation are measured. Recrystallization is similar on ZnO and FTO but different on ITO. The performance of solar cells on different TCOs depends on the amount (thickness) of CdCl2. For higher efficiencies, more CdCl2 is required for CdTe/CdS/FTO in comparison to CdTe/CdS/ITO.