High Efficiency and Stable CdTe/CdS Thin Film Solar Cells on Soda Lime Glass

Stable CdTe/CdS thin film solar cells which exhibit a conversion efficiency around 15% were prepared on soda lime glass substrates. These results were obtained by intervening on three important layers, which compose the cell namely the front contact, the CdS film and the back contact. The front transparent contact was prepared by depositing in sequence an Sn02 and an ITO film, the first one to passivate the glass against Na diffusion and the second one to get a low sheet resistance. CdS films deposited by sputtering were treated with CdCl2 at 500°C in air for 15 min. This treatment improves both the transparency and the crystallinity of the CdS film. Finally, as a back contact, Sb2Te3, which is a low gap compound exhibiting p-type conduction with a very low resistivity, was used. This contact secures the stability of the cell.