Photoluminescence-excitation spectra of copper iodide single crystals

The excitation spectra of 'edge' luminescence (i.e., near the edge of self-absorption) in single crystals of CuI were investigated. It is shown that the excitation of orange and red luminescence occurs not only in the case of interband energy absorption, but also in longer-wavelength bands with maxima at 417.5-419, 423, 430-435, and 480 nm. Experimental data on edge emission and excitation spectra make it possible to conclude that energy absorption in donor-acceptor pairs localized near corresponding luminescence centers plays a major role in photoexcitation processes in CuI.