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Radiative Donor-Acceptor Pair Recombination in Tl2Ga2Se3S Layered Single Crystals

The emission band spectra of Tl2Ga2Se3S layered crystals have been studied in the temperature range of 10-50 K and in the wavelength region of 540-700 nm. A broad photoluminescence band centered at 626 nm (1.98 eV) was observed at T = 10 K. Variation of emission band has been studied as a function of excitation laser intensity in the 0.4-51.5 mW cm(-2) range. The analysis of the spectra reveals that the peak energy position changes with laser excitation intensity (blue shift). This behavior of the emission band is in agreement with the idea of separation inhomogeneity of donor acceptor pairs. Radiative transitions from the moderately deep donor level E-d = 270 meV to the shallow acceptor level E-a = 10 meV were suggested to be responsible for the observed photoluminescence band.