Copper indium gallium (di)selenide (
CIGS) is a
I-
III-
VI2 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
xGa
(1-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 the
chalcopyrite crystal structure, and a
bandgap varying continuously with
x from about 1.0 eV (for copper indium selenide) to about 1.7 eV (for copper gallium selenide).