ITO has unique properties to be used as front electrode in CdS/CdTe solar cells, however ITO is expensivenot abundant and consequently this type of solar cells is still relatively expensive. This work studies theusing of ZnO and ZnO based alloys such as ZnO:Sn, ZnO:Al and ZnO:In as alternative materials of ITO inorder to develop the efficiency of CdS/CdTe solar cells. Both optical and recombination losses have beentaken into consideration. The calculation of optical losses is carried out based on the multiple reflectionseffect as well as absorption in TCO and CdS layers. Both the front and back surfaces recombination ofthe CdTe layer are used to describe the recombination losses. It was found that ZnO and its alloys areconsidered good alternative materials of ITO that used as a front contact in CdS/CdTe cells. The bestresults were obtained for ZnO:Al, where the calculated short-circuit current density is 22.64 mA/cm2atwidth of depletion layer of 0.11 m, the optical and recombination losses are about 27% and the CdS/CdTeefficiency is about 17.9%.