Characterization of Cu(In,Ga)3Se5 Thin Film for Top Cell in CIGS Tandem Solar Cells

Abstract

Cu(In,Ga)3Se5 films were deposited on soda-lime glass substrate by three-stage co-evaporation process. In the film, the band gap increased as the Cu content decreased and also as the Ga content increased. The grain size became smaller as the Ga content increased. In the Cu1.29(In1-xGax)3Se5 system, the maximum hole concentration was 1x1015 /cm3 when the Ga content was 0.5 and its band gap was 1.45 eV. Comparing the conventional CIGS solar cell with Cu0.8(In0.7Ga0.3)Se2 film, the series resistance is too large, indicating that further p-type doping in the Cu(In,Ga)3Se5 film is necessary to improve cell efficiency for the top cell application in CIGS tandem solar cells.