CdS homojunction solar cell having an improved efficiency of 3% has been fabricated. This is achieved by the uniform distribution of copper into the n-CdS film by repeated thermal annealing of copper coated on the n-CdS. The ESCA analysis (Electron Spectroscopy for Chemical Analysis) gives the idea that no copper compounds like CuxS has not been formed. The depth profile of the sample showed that the copper distribution on the top layer of the CdS is uniform and then existed n-CdS layer below the p-CdS:Cu layer. free of copper atoms. The optical absorption studies on the sample revealed that there is a slight modification of optical band gap, for the copper diffused p-CdS. The spectral response curve for the cell has also been drawn.