Radiative recombination in crystallineAs2S3

Abstract

Two photoluminescence bands characterized by their excitation energy are observed in orpiment ($c-{\mathrm{As}}_2{\mathrm{S}}_3$). We assign the emission band with the peak energy of 1.53 eV to defect-related bound-exciton recombination. The luminescence band at 1.25 eV is induced by band-to-band excitation and may be understood by the self-trapping of an exciton.