Photoluminescence properties of stoichiometric CuInSe2 crystals

We studied photoluminescence (PL) properties of stoichiometric CuInSe2 (CIS) single microcrystals. Temperature and laser power dependencies of the PL spectra were measured. Two bands at 0.973 (A-band) and 0.991 eV (B-band) governed the obtained PL spectra. Measured dependencies showed very similar properties for both bands: the j-shift that was generated by altering the laser power was 2 meV per decade for both bands and thermal activation energies were 46 and 32 meV for A- and B-band, respectively. Based on these results, we assume that both bands come from the same shallow donor–shallow acceptor recombination process with different bandgap energies for CIS. The solid solution phase of CIS with K or Na is proposed as the source of distinctive bandgap.