Scalability and pilot operation in solar cells of CuInSe2 and their alloys

The compound Cu(Ga,In)Se2 (CIGS), and related compounds, have demonstrated their high potential for high-efficiency thin-film solar cells up to levels approaching 18%. It is expected that this quality can be further improved by optimizing process conditions and combining the CIGS with other group I, III and VI elements. Other material combinations are under development. Several companies and research institutes are developing CIGS-based technology with the aim of low cost/high volume production. The key process is a scalable technology to fabricate highest quality CIGS films on a large area with high throughput and process yield. The Centre for Solar Energy and Hydrogen Research (ZSW) and the University of Stuttgart (IPE) are working together on CIS technology. On the module basis ZSW is negotiating with private companies to commercialize module technology. These activities are compared with others worldwide. With the aim of developing relevant high-volume fabrication technologies, all laboratory deposition techniques that have proven highest device performance are applied also on the module level to prevent physical and chemical effects that could limit device performance. All film deposition techniques are developed for high-vacuum in-line fabrication on a large area except for the buffer layer of CdS, and monolithic integration is realized by patterning steps. Modules are prepared on substrate areas of 10×10 up to 30×30 cm2. Actual results of modules of these sizes are 14% and 10%, respectively. Estimations of fabrication costs with increasing fabrication volume show that it is possible to produce CIGS modules at costs well below US$1 W−1p.