Absorber processing issues in high-efficiency, thin-film Cu(In,Ga)Se2-based solar cells

Abstract
Three approaches to thin‐film Cu(In,Ga)Se2 absorber fabrication are considered. They are generically described in terms of the sequential or concurrent nature of source material delivery, selenium delivery, and compound formation. A two‐stage evaporation process successfully produced the absorber component of a world‐record, 17.1% efficient solar cell. Alternative approaches that reduce the requirements for high substrate temperatures are considered. The relationship between absorber process parameters, band gap profile, and device performance are examined. Engineering the [Ga]/([Ga]+[In]) profile in the absorber has led to the reported advances.