Abstract
Thin films of CuInxGa1-xSe2 were produced over the entire range of 0≤x≤1 by rf sputtering. The optical absorption coefficients of the CuInxGa1-xSe2 thin films were determined from the measured transmittance and reflectance in the wavelength range of 400 to 2000 nm. The optical absorption spectra for sputtered CuInxGa1-xSe2 thin films (x≠0) show three energy gaps, which are attributed to the fundamental edge, and band splitting by crystal-field and spin-orbit splitting, respectively. The primary transition energies exhibit bowing behavior expressed by the relationship Eg1=1.674-0.803x+0.130x2. The second and third transition energies are 0.06-0.08 eV and 0.22-0.27 eV above the primary transition energies, respectively.