POF III / Topic 1 Solar cells of next generation
Subtopic 2 - Compound Semiconductors
Thin-film photovoltaic (PV) modules are a promising alternative to crystalline silicon-based devices when it comes to Terawatt-scale deployment of photovoltaic modules. In particular chalcopyrite Cu(In,Ga)(Se,S)2 (CIGS) based solar cells offer conversion efficiencies exceeding 22% and can compete with crystalline silicon solar cells. Additionally, thin-film deposition techniques allow the use of flexible substrates such as polymer or metal foils and convenient integration into building components like facades or roof tiles. However, there are several challenges when it comes to thin-film compound materials:
- Transfer of high efficiency of small laboratory devices to large area modules
- Reduction of manufacturing cost by developing fast, low-cost deposition with minimized material usage
- Avoiding toxic and rare elements
The CIGS-Teams at PVcomB follow two main routes for the formation of CIGS, which are both technologically relevant: A three-stage coevaporation [PVD-CIGS] process that yields high-efficiency devices on small substrates (5 x 5cm2) and a 30 x 30 cm² research line following the sequential processing route [RTP-CIGS] by firstly depositing metal precursor layers followed by an atmospheric pressure rapid-thermal processing (AP-RTP) in elemental selenium (Se)- or sulfur (S)-vapor to form Cu(In,Ga)(Se,S)2 absorber layers.