Structural, optical and electrical properties of CuIn5Se8 and CuGa5Se8

Ingots of CuIn5Se8 and CuGa5Se8 were prepared by direct fusion of the stoichiometric mixture of the elements. The analysis of X-ray powder diffraction data showed the presence of one single phase with tetragonal structure for CuGa5Se8 and two phases with hexagonal and tetragonal structure for CuIn5Se8. The lattice parameters a and c were refined by means of the program NBSAIDS83. The phase transition temperatures were obtained by Differential Thermal Analysis measurements performed on samples sealed in evacuated quartz ampoules. Transmittance measurements were used to determine the absorption coefficient a. The values of Eg were obtained. The electrical resistivity was measured from 10 to 400 K using a four-wire configuration. The activation energies were estimated from the Arrhenius plot of the resistivities. 18 refs.