Highly efficient CIS solar cells and modules made by the co-evaporation process

Thin-film photovoltaic modules which use the chalcopyrite Cu(In,Ga)(Se,S)2 (CIGS) as the light-absorbing layer have now entered the decisive industrial phase. Companies located mainly in Germany and Japan will produce more than 100 MWp CIGS modules in 2008, demonstrating that the CIGS technology has already achieved a certain maturity. Whereas key features of the technology are already well-optimized, there are several approaches to further improve the productivity of new lines. The ZSW operates a line for 30 × 30 cm2 modules in which all process steps – from glass cleaning to module encapsulation – are being developed. A major goal of the development is the very fast and efficient transfer of promising new materials and processes from cells to the industrial module level. Therefore, ZSW is focusing on processes like the in-line co-evaporation method for CIS or chemical bath deposition for buffer layers to optimize the junction. We could demonstrate efficiencies close to 18% for small test cells and 14–15% for modules with modified processes. Different cell and material data from optoelectronic measurements and microscopic analysis will be presented in this contribution.