Study of Indium Non-stoichiometry in CuInTe2 and Its Effects on the Thermoelectric Properties

Abstract

CuInTe2 is a ternary chalcopyrite of the type I-III-VI2 (where I=Cu, Ag; III=Al, Ga, In; and VI=S, Se, Te). This group of materials represents a broad class of semiconductors with potential applications in optoelectronics and photovoltaics and could be interesting thermoelectric materials in the middle temperature range. CuInTe2 is able to show relatively large stoichiometric deviations due to the low energies of formation of native defects. In this work, the effects of non-stoichiometric indium on the transport and thermoelectric properties of the CuIn1-xTe2 system are systematically studied in the x range of -0.01 to 0.06. The results x-ray diffraction, differential thermal analysis and scanning electron microscopy measurements suggest that eutectoid of Cu-Te is present as an extraneous phase in most of the prepared samples. Moreover, the chemical composition of the extraneous phases is temperature-dependent, and thus the chemical composition of the main phase is equally so. The observed changes in all the studied transport and thermoelectric parameters upon varying the indium stoichiometry support the idea that unlike the Cu sublattice, the indium sublattice in CuInTe2 can be doped to improve the thermoelectric properties of the material.