Thin film solar cells were developed as an alternative to c-Si solar cells in an effort to bring down the cost. Among these the CdS/CdTe solar cell, has a high conversion efficiency as well as capability to be produced at low cost. The heterojunction CdS/CdTe solar cell shows a high spectral response in the wavelength region from 500 nm while it is much less sensitive for the region below 500 nm due to the absorption in the CdS window layer. It is suggested thatsolar spectrum can be shifted using SrB4O7:Sm2+phosphor which will absorb radiations in the wavelength region 300-500 nm and emit around 650-750 nm. This can improve the efficiency of CdS/CdTe solar cell.