Optical gap of a new cubic ordered compound CuIn2Se3.5

Optical absorption results in the band edge region are reported for the first time on a new cubic ordered phase, lately evidenced, with a composition close to CuIn2Se3.5. The optical gap Eg of this semiconducting compound was deduced to be about 1.05 eV at room temperature, which is nearly 100 meV greater than that of the chalcopyrite CuInSe2. It was observed to increase with decreasing temperature.