Properties of CuInSe2 and Mo thin films produced by pulsed d.c magnetron sputtering for solar cell fabrication
Copper indium diselenide (CIS) is one of the most promising semiconducting thin film materials used in the solar cell industry. A typical CIS based solar cell comprises a Mo/CuInSe2/CdS/i-ZnO/ZnO heterojunction. This work describes the use of pulsed d.c magnetron sputtering (PDMS) to produce CIS and molybdenum thin film layers from powdered targets. This is a widely accepted method for the deposition of dielectric materials and for reactive sputtering but has not generally been applied to solar cell fabrication. CuInSe2 films form the absorbing layer of the cell. Growth of stoichiometric p-type CuInSe2 with the desired properties has always been a challenge. This technique offers a single step process for depositing CIS films. Films were deposited at room temperature from polycrystalline powders with various starting compositional ratios. The deposited films were found to be nearly stoichiometric for a wide range of powder compositions. They were p-type and pin hole free. Molybdenum layers, used as the back contact, were found to have low resistivity, were also pinhole free and adhered well to the glass substrate. The physical, structural and electrical properties of these films were analysed using SEM, AFM, EDX, XRD, four point probe and hot probe methods.