Optical properties of copper indium diselenide near the fundamental absorption edge

In this work we report on an optical absorption study near the band gap of n-type ${\mathrm{CuInSe}}_2$ at 7 K. From the analysis of the results the energy gap is found to be 1.02±0.01 eV. The binding energy of the exciton and the ionization energy of acceptors and donors are determined to be 18, 54, and 26 (±5) meV, respectively. It is suggested that ${\mathrm{In}}_{\mathrm{Cu}}$ antisite donors and $V_{\mathrm{Cu}}$ acceptors are the predominant active intrinsic defects in ‘‘In-rich’’ ${\mathrm{CuInSe}}_2$.