Studies on substrates and contacts for CIS films and devices

Nature of the glass/Mo substrates used in CIS solar cell structures influences the performance of the devices. Excessive Na diffusion from the commonly used soda-lime glass substrates through the Mo layer and its reaction with the processing atmosphere at the Mo/CIS interface may limit the efficiency of cells due to the formation of a high resistivity layer near this contact. A moderate level of Na diffusion, on the other hand, improves the efficiency of the cells, especially those fabricated on CIS films with low Cu/In stoichiometric ratios. The Na diffusion process depends on the type of glass substrate used and the nature of the Mo layer.