Simultaneous optimization of the overall thermoelectric properties of Cu₃SbSe₄ by band engineering and phonon blocking

It is a challenge to optimize the coupled electrical and thermal transport properties of a thermoelectric material simultaneously. Here, the enhancement of overall thermoelectric properties in Cu₃SbSe₄ has been demonstrated through Te substitution. The results display that the simultaneous optimization of the Seebeck coefficient, electrical conductivity and thermal conductivity is realized after Te-doping and thus yielding considerable enhancements in ZT values in the whole temperature range as comparison to that of pristine Cu₃SbSe₄. In Te-doped Cu₃SbSe₄ system, the reduction of electrical resistivity is due to the narrowed bandgap; the enhanced Seebeck coefficient stems from the increased density of states near the Fermi level; and the suppressed thermal conductivity is related to the introduced phonon blocking from point defect scattering or softening of chemical bond interaction. This work can also offer a referential route to boost the overall thermoelectric properties by isovalent doping with heavy element for other thermoelectric materials.