Copper indium gallium (di) selenide (CIGS) is a I-III-VI 2 semiconductor material composed of copper, indium, gallium, and selenium. The material is a solid solution of copper indium selenide (often abbreviated “CIS”) and copper gallium selenide. It has a chemical formula of CuIn (1-x) Ga (x) Se 2 where the value of x can vary from 1 (pure copper indium selenide) to 0 (pure copper gallium selenide). CIGS is a tetrahedrally bonded semiconductor, with chalcopyrite crystal structure, and a bandwidth of 1.5 eV (for copper indium selenide) to about 1.7 eV (for copper gallium selenide).

CIGS is a tetrahedrally bonded semiconductor, with the chalcopyrite crystal structure. On heating and transformations to the zincblende form and transition temperature decreases from 1045 ° C for x = 0 to 805 ° C for x = 1.

It is best known for the material for CIGS solar cells in thin-film technology used in the photovoltaic industry. In this role, CIGS has the advantage of being able to be deposited on flexible substrate materials, producing highly flexible, lightweight solar panels. Improvements in efficiency have made CIGS an established technology among alternative cell materials.