Excitation and temperature tuned photoluminescence in Tl2In2S3Se layered crystals

Photoluminescence spectra of Tl2In2S3Se layered single crystals have been studied in the wavelength region of 535-725 nm and in the temperature range of 22-58 K. Two photoluminescence bands centered at 564 (2.20 eV, A-band) and 642 nm (1.93 eV, B-band) were observed at T = 22 K. Variations of both bands have been investigated as a function of excitation laser intensity in the range from 16 to 516 mW cm(-2). These bands are attributed to recombination of charge carriers through donor-acceptor pairs located in the band gap. Radiative transitions from shallow donor levels located 0.02 and 0.01 eV below the bottom of conduction band to acceptor levels located 0.05 and 0.44 eV above the top of the valence band are suggested to be responsible for the observed A- and B-bands in the photoluminescence spectra, respectively.