New developments in Cu(In,Ga)(S, Se)2 thin film modules formed by rapid thermal processing of stacked elemental layers

A second-generation process for high-efficiency large-area Cu(In,Ga)(Se,S)2 thin film (CIGSSe) solar modules has been developed applying controlled sodium doping and rapid thermal processing for absorber formation. The pilot line delivers aperture area efficiencies of 12.2%±0.5% (average) for 30×30 cm2 modules and a certified champion efficiency of 13.1% for an unencapsulated 60×90 cm2 demonstrator module. The stability of the frameless pilot line modules with a low-cost package against humidity is confirmed externally by passing the damp heat test sequence according to IEC 61646. Substitution of CBD-CdS by CBD-Zn(S, OH) buffer layers yields efficiencies up to 12% on 30×30 cm2 circuits. First CIGSSe-cells on flexible substrates were also developed applying 30 μm thin titanium foils, 8×8 cm2 in size. Average cell efficiencies on a substrate up to 12.4% were achieved.