Copper indium gallium selenide (CIGS) absorber based solar cell generally use CdS as a buffer layer. In large scale utilization of this kind of solar cell there is a debate on the CDS which comprises with toxic Cd. In this research different non-toxic materials have been studied observing the suitable energy band bending, potential of light insertion on the absorber layer and other electrical output parameters for optimum efficiency. From the research it has been revealed that out of single layer ZnS, ZnSe, ZnTe, SnO2, In2S2 and double layerZnSe-In2S2,ZnS-CdS materials the double layer ZnSe-In2S2 has an excelled impact on the band alignment and shows an efficiency around the conventional single layer CdS based CIGS solar cells, ~21%. Hence this double layer ZnSe-In2S2 can be an alternative of the toxic Cd based CdS in CIGS solar cells. Keywords—Photoconversion efficiency, toxicity, dual buffer layer, band alignment, Thin film solar cells (TFSC).