Influence of the carrier concentration on the optical absorption edge of n-CuInSe2

The absorption spectra of as-grown and copper-annealed n-CuInSe₂ samples were obtained at room temperature. A shift of the absorption edge to higher energy for the annealed sample as compared to its value in the as-grown sample, is observed in the measurements. This behaviour can be explained as due to the fact that n-CuInSe₂ becomes degenerate at relatively low electron concentration because of its small electron effective mass.