Growth and properties of single crystals of the ternary CuIn5Se8 compound

Single crystals of the CuIn5Se8 compound have been synthesized by the directed crystallization of the melt in a single-zone furnace (vertical Bridgman variant), starting from the stoichiometric mixture of constituent elements. Phase purity of the synthesized material was confirmed by powder X-ray diffraction. Transmittance as a function of wavelength was recorded in the wavelength range of 0.5-2.500mum at different temperatures. Band-to-band transition energies were calculated from the transmission spectra in the region of the fundamental absorption edge. From the energy gap Eg temperature dependence the Debye temperature ThetaD=215+/-8K was deduced. The photoluminescence spectra of the CuIn5Se8 crystals were detected in the temperature range from 10 to 300K at various powers of laser excitation. The spectra exhibit emission band localized at 1.00eV which can be attributed to the donor-acceptor-pair recombination.