Published online by Cambridge University Press: 01 February 2011
The pentenary chalcopyrite compound Cu(InGa)(SeS)2 provides several potential advantages over Cu(InGa)Se2 as the absorber layer in thin film solar cells, especially with wide bandgap alloys. The effects of S addition to the quaternary alloy are investigated with films deposited by elemental thermal co-evaporation and by the reaction of metallic precursors in hydride gases. With co-evaporated films the addition of S complicates the control of composition through the film. The incorporation of the chalcogen species Se and S depend on the relative Cu in the film and, for films with excess Cu, on the relative group III composition. For the precursor reaction process the addition of S by the inclusion of H2S gas in the reaction enables control of the relative Ga concentration and bandgap of the film. With both processes the incorporation of S during deposition also effects the morphology and grain size. The co-evaporated films have smaller grains with S while the reacted films have larger grains which may be due to the higher TSS the S reaction enables.