Defect Level Identification in CuInSe₂ from Photoluminescence Studies

By correlating photoluminescence data with the electronic properties, stoichiometry, and chemical diffusion coefficients (of Cu) for a number of single-crystal samples, we arrive at a chemically and physically consistent interpretation of luminescent transitions in CuInSe₂. This interpretation involves point defect chemical assignments to the electron energy levels that are involved in these transitions. Thus the copper vacancy, V_Cu, is identified as a defect that is mainly responsible for Cu diffusion in this material. The electrochemical potential of the electron involved in the V_Cu^x + e⁻ = V_Cu′ reaction is found to be ca. 40 meV above the valence band.