Crystal structure, electrical, and optical properties of Cu3In7Te12 ordered defect semiconducting compound

CuInTe2 chalcopyrite semiconductor and the ordered defect compounds of the Cu2Te-In2Te3 pseudo-binary system have recently emerged as suitable candidates for thermoelectric applications. In this article, the crystal structure, optical, and electrical properties of Cu3In7Te12, a member of this ternary system, have been studied. It was established that this material crystallizes in a tetragonal structure with space group P (4) over bar 2c. The analysis of the optical absorption spectrum near the fundamental absorption edge shows that the energy gap is direct and the band gap varies from 1.030 to 0.952 eV between 10 and 300 K. From the analysis of electrical data, it was found that above 160 K, the electrical conduction is due to the activation of a shallow acceptor level of about 10 meV, and the value of the hole-effective mass is mh = (1.18 +/- 0.35) me. In the temperature range from 160 to 130 K, variable range hopping (VRH) mechanism of Mott-type in the impurity band is observed. At high temperatures, the mobility is explained by taking into account the scattering mechanism of the charge carriers by donor-acceptor defect pairs, ionized and neutral impurities, acoustic and non-polar optical phonons. In the low temperature region, the mobility data can be explained by an expression related to Mott law for VRH conductivity. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim