Electronic, Thermal, and Thermoelectric Transport Properties of ReSe2 and Re2Te5

Abstract

Re-based chalcogenides have been studied in various fields such as strain engineering, photodetection, spintronics, and electromechanics, as well as in piezoelectric and photonic devices. In this study, the electrical, thermal, and thermoelectric transport properties of two representative Re-based chalcogenides, ReSe2 and Re2Te5, are investigated systematically. Furthermore, their electronic band dispersions are calculated using density functional theory and compared with the phenomenological data. The maximum power factor values for the ReSe2 and Re2Te5 were measured 0.0066 and 0.11 mW/mK2 at 880 K, respectively. Thermal conductivity of layered ReSe2 at room temperature was between 1.93 and 8.73 W/mK according to the measuring direction. For Re2Te5 with a complex orthorhombic crystal structure, the thermal conductivity was quite low in the range between 0.62 and 1.23 W/mK at room temperature. As a result, the maximum $zT$ values of ReSe2 were quite low as 0.0016 at 880 K due to very low power factor and high thermal conductivity. Meanwhile, the relatively high $zT$ of 0.145 in Re2Te5 is obtained at 880 K, which is originated from the acceptable power factor value and the low thermal conductivity.