Variation of Cu content of sprayed Cu(In,Ga)(S,Se)2 solar cells based on a Thiol-Amine solvent mixture

Cu(In,Ga)(S,Se)2 (CIGS) thin films were formed by a low cost solution-based approach using metal sulfide precursors. The stoichiometry of the absorber layer is tailored in order to improve film morphology and electrical properties. Cuy ln0.7Ga0.3Se2 films were prepared with a varied Cu content (0.8>y>1.1) and were completed in solar cell devices. The compositional, structural and electrical properties of the devices were investigated. Increased Cu content improves lateral crystallization, but results in the formation of Cu-rich secondary phases in-between CIGS grain boundaries. Characterization of the completed devices shows that Cu content has an important effect on the device electrical properties and the dominant recombination mechanisms.