Cu(In,Ga)Se2 solar cells and mini-modules fabricated on thin soda-lime glass substrates

In this paper, we report a recent progress in Cu(In,Ga)Se-2 (CIGS) solar cells and mini-modules demonstrated on soda-lime glass (SLG) substrates, which are one of the most common and cost effective substrate materials for chalcopyrite photovoltaics. CIGS absorber layers grown by the three-stage co-evaporation process was used with an optimized [Se]/[metal] flux ratio and preferable substrate temperatures for SLG substrate thicknesses. SLG substrates of 0.28-1.1 mm in thickness, which are thinner than that generally used in laboratories and industries (similar to 2-3 mm), were employed to develop techniques for further reductions of material cost and module weight. Solar cell and mini-module efficiencies of > 19% and > 17%, respectively, with relatively high open circuit voltages (V) and fill factors (FF) (V-oc 0.77 V and FF 0.79 for cells, and V-oc 0.77 V and FF 0.74 for mini-modules) were demonstrated using a composition ratio [Ga]/([In]+[Ga]) of 0.45 for the CIGS absorber layers. Key techniques and future directions toward highly efficient CIGS solar cells and modules with high values of V., and FF are discussed. (C) 2013 Elsevier B.V. All rights reserved.