 It has a chemical formula of CuIn(1-x)Ga(x)Se2 where the value of x can vary from 0 (pure copper indium selenide) to 1 (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).CIGS is a tetrahedrally bonded semiconductor, with the chalcopyrite crystal structure.