Radiative recombination pathways in ordered and disordered CZTSe microcrystals

The photoluminescence (PL) spectra of Cu2ZnSnSe4 microcrystals with two different degrees of disorder were investigated by measuring the dependencies on the temperature and excitation power. Crystals were cooled at different rates after the high-temperature annealing treatment in order to change the degree of disorder. The PL spectra of both samples consist of one asymmetrical band located at 0.88 and 0.92 eV for disordered and ordered crystals, respectively. At low temperatures, both samples have similar origins of PL involving localized electron states. In the case of the ordered sample, we observed deeper localized electron states, thus higher temperatures were needed to empty the electrons from these states to the band states. Changes in the degree of disorder lead to changes in the radiative recombination in CZTSe microcrystals.