All thin film solar cells require the use of transparent conductive electrodes such as indium tin oxide (ITO) due to its unique combination of transparency, high conductivity, durability, and favourable surface properties. Indium, however, is a rare and expensive metal; proposed large-area installations of photovoltaic (PV) cells will add further strain to global indium supply. Transparent conductive materials that are abundant, inexpensive, and enable efficient thin film solar cells must therefore be developed. Zinc oxide (ZnO), tin doped zinc oxide (ZnO:Sn), aluminum doped zinc (ZnO:Al) and indium doped zinc oxide (ZnO:In) were theoretically investigated as alternatives transparent conductive oxides (TCO) to indium tin oxide that used as front electrode in CdS/PbS thin-film solar cells. The effect of optical and recombination losses as well as the reflectivity from metallic back contact were investigated in this work. It was found that the spectral quantum efficiency depends on the width of space-charge region (W) and the thickness of absorber layer (dPbS). The maximum short-circuit current density of about 20.9 mA/cm2 was achieved at W= 3μm and dPbS=2μm for ZnO:Al. The average optical losses due to reflection from all interfaces and due to absorption in CdS and TCO layers were about 32%. The total reflected back contact lead to increase the short-circuit current density by 20% and hence the efficiency of CdS/PbS cell recorded a value of 7.89 % for ZnO:Al.