The role of structural properties on deep defect states in Cu_2ZnSnS_4 studied by photoluminescence spectroscopy

摘要

In this study, we investigated the photoluminescence (PL) properties of Cu_2ZnSnS_4 polycrystals. Two PL bands at 1.27 eV and 1.35 eV at T = 10 K were detected. Similar behaviour with temperature and excitation power was found for both PL bands and attributed to the band-to-impurity recombination. Interestingly, the thermal activation energies determined from the temperature dependence of the PL bands coincide. With the support of the Raman results, we propose that the observed PL bands arise from the band-to-impurity-recombination process involving the same deep acceptor defect with ionization energy of around 280 me V but different Cu_2ZnSnS_4 phase with different bandgap energy.