In the case of solar cells, research is being conducted into combinations of elements that are cheaper to manufacture and more efficient than the various silicon structures. Copper indium diselenide (CIS) and copper indium gallium selenide (CIGS) are such element combinations, which have already been used in solar technology
. As far as efficiency is concerned, this is around 15 %. In research laboratories, solar cells with an efficiency of over 20 % have already been produced.