Abstract: A nano structure CdTe/CdS Photon Trapping Solar Cell (PTSC) comprising an ultra thin film stack construction of 2 layers, one each of Cadmium Sulfide and Cadmium Telluride, and wherein the bottom electrode is a reflecting sheet or plate that serves to reflect Photons unabsorbed by their pass through the material back through the layers of Cadmium Telluride and Cadmium Sulfide. The bottom metallic plate also serves as an electron conductor for allowing the photoelectric current to exit the device and perform useful work. The cell has a maximum efficiency of 40%.