Low-temperature photoluminescence in CuIn5S8 single crystals

Photoluminescence (PL) spectra of CuIn5S8 single crystals grown by Bridgman method have been studied in the wavelength region of 720-1020 nm and in the temperature range of 10-34 K. A broad PL band centred at 861 nm (1.44 eV) was observed at T = 10 K. Variations of emission band has been studied as a function of excitation laser intensity in the 0.5- 60.2 mW cm(-2) range. Radiative transitions from shallow donor level located at 17 meV below the bottom of the conduction band to the acceptor level located at 193 meV above the top of the valence band were suggested to be responsible for the observed PL band. An energy level diagram showing transitions in the band gap of the crystal has been presented