In this paper we report for the first time the results of photoluminescence (PL) and photoconductivity (PC) measurements on stoichiometric and well-defined off-stoichiometric copper indium diselenide. The energy gap at 10 K is 1.050±0.005 eV and free-exciton emission at 1.030±0.005 eV is the dominant feature in the PL spectra of stoichiometric nominally undoped ${\mathrm{CuInSe}}_2$. For Cu:In and metal:selenium ratios >1 recombination between Se-vacancy donors (-70 meV versus the conduction-band edge ${\mathrm{Cu}}_{\mathrm{In}}$ antisite acceptors [40 meV versus the valence-band edge (VBE)], and In-vacancy acceptors (80 meV versus the VBE), respectively, dominates the PL spectra. Excitation from the above two acceptor states contributes to the PC spectra with complimentary temperature dependence as compared to the deep emission.

• Received 13 December 1984

DOI:https://doi.org/10.1103/PhysRevB.31.4074