Chemical surface deposition of ultra-thin cadmium sulfide films for high performance and high cadmium utilization

Chemical surface deposition (CSD) of CdS films is described. In this process, heat from the substrate provides the energy needed for reaction at the surface, resulting in heterogeneous deposition. Deposition from an aqueous solution containing cadmium species, thiourea and ammonia yields dense conformal CdS films, with > 90% utilization of Cd species. The CdS films exhibit negligible occurrence of pinholes and particulates, making CSD films suitable for inclusion in substrate or superstrate solar cell designs. The optical and structural properties of CSD CdS films on polycrystalline substrates are reported. Device results are presented for CdTe and Cu(InGa)Se/sub 2/ solar cells using CSD CdS window layers.