Photoluminescence of Ag8SnSe6 argyrodite

A basic study of the low-temperature photoluminescence of an Ag8SnSe6 argyrodite compound is reported. Measurements were performed on wafers grown by the direct melting of a high-purity stoichiometric mixture of elementary Ag, Sn, and Se in a sealed silica ampoule. Two peaks with maxima located at 0.85 and 0.95 eV were visible in the photoluminescence spectra of an Ag8SnSe6 argyrodite. The temperature and excitation dependences of the dominant peak at 0.85 eV suggest that this transition can be associated with donor-acceptor recombination. The activation energies of the defects involved in this transition were calculated based on temperature-dependent photoluminescence and transmission measurements. We found the ionization energies to be at 44 and 72 meV for the shallower and deeper defects, respectively. The second peak in the spectra at 0.95 eV was assigned to a band-to-band transition or a transition between band tails.