Thin film solar cells based on copper-indium-gallium-selenide (‘CIGS’) nor have reached very high energy conversion efficiencies up to 20 %, and are on the verge of industrialisation. Hitherto, only very pure materials were used. As purity adds to production cost, it is now becoming important to asses the influence of the materials purity on the solar cell’s performance. Umicore will take care of the materials, solar cells will be made at EMPA (Zürich), and the influence of defects and impurities to cell performance will be studied in UGent.