Two impurity energy level regulation leads to enhanced thermoelectric performance of Ag1−xCdxIn5Se8

Abstract

The tetrahedrally bonded diamond-like compound AgIn₅Se₈ is proved to be a promising thermoelectric material due to its intrinsically low thermal conductivity. For the pristine AgIn₅Se₈ compound, however, the inferior electrical properties generally result in a limited zT value, owing to its wide band gap, up to 1.1 eV. Here, we report on the synthesis of AgIn₅Se₈ compound through a quick and convenient solid-state reaction route. Furthermore, the two impurity energy levels are regulated in those doped samples by incorporating Cd²⁺ ions at Ag⁺ lattice sites; the electron concentration dramatically increases, resulting in greatly enhanced electrical conductivity and thus a thermoelectric power factor over the entire temperature range. Combined with the intrinsically low lattice thermal conductivity, Cd-doped Ag_1−xCd_xIn₅Se₈ with x = 0.05 reaches the highest zT value of 0.63 at 883 K, favorably improved by 40% compared with that of the pristine AgIn₅Se₈.