CIGSSe thin film PV modules: from fundamental investigations to advanced performance and stability

Abstract A process for high efficiency large area Cu(In,Ga)(Se,S) 2 (CIGSSe) thin film solar modules is developed applying rapid thermal processing and controlled sodium doping. Continuous optimization aims at sufficient process maturity for a successful transfer into cost-effective mass production. The pilot line yields aperture area efficiencies of 11% (average) for 30×30 cm 2 modules and a certified champion efficiency of 13.1% for the first 60×90 cm 2 demonstrator module (unencapsulated). First Cd-free 30×30 cm 2 circuits yield up to 11.9% efficiency applying CBD-Zn(S,OH)-buffer layers. Investigations on the absorber formation by structural, compositional and electrical characterization will be given. Models for the Ga and S distribution will be discussed and experimentally verified. A favorable double band gap grading structure is accomplished by controlled sulfur profiling and by a process induced gallium accumulation towards the back electrode. The stability of the frameless low-cost packaged pilot line modules against humidity is confirmed externally by passing the damp heat test sequence according to IEC 61646.