Modification of the intermediate band and thermoelectric properties in Se-doped CoSbS1−xSex compounds

Abstract

Paracostibite (CoSbS), a naturally occurring mineral composed of earth abundant elements, is a newly developed and environmentally friendly thermoelectric material for medium temperature power generation applications, and has attracted considerable attention. In this work, in order to study the influence of Se doping on the site of S, CoSbS_1−xSe_x (0 ≤ x ≤ 0.09) compounds were synthesized by vacuum melting and annealing and compacted by spark plasma sintering. Alloying S with Se decreased the band gap and the impurity activation energy. Moreover, Se substitution on the site of S not only improved the electronic transport properties, but it also dramatically suppressed the thermal conductivity. The maximum power factor as high as 1.1 × 10⁻³ Wm⁻¹ K⁻² was achieved in CoSbS_0.99Se_0.01 at 900 K. Due to the improved power factor and the decreased thermal conductivity, the ZT reached 0.26, exceeding the figure of merit of undoped CoSbS by about 37%.