The band-edge luminescence of single crystals was studied at temperatures of between 2 and 300K. Sharp emission lines were attributed to the decay of free and bound excitons, and their phonon replica. Analysis of the peak position revealed values of 0.0044eV and 1.044eV for the binding energy of the free exciton and the band-gap at 2K, respectively. Investigations of n-type and p-type material revealed different emission lines, which were attributed to excitons that were bound to the various predominant intrinsic defects in the materials.

Excitonic luminescence in CuInSe2 J.H.Schön, E.Bucher: Applied Physics Letters, 1998, 73[2], 211-3