Novel p-type thermoelectric materials Cu3MCh4 (M = V, Nb, Ta; Ch = Se, Te): high band-degeneracy

Abstract

The good thermoelectric performance of some half-Heusler (HH) alloys has been stimulating substantial efforts in searching for more materials with similar crystal structures but better properties. In this work, we predict a new class of thermoelectric materials Cu₃MCh₄ (M = V, Nb, Ta; Ch = Se, Te) with similar lattice structures to HH alloys. The electronic and thermal transport properties of these materials are quantitatively evaluated using first-principles calculations in combination with the semi-classical transport theory. The largest ZT values at 1000 K for p-type Cu₃MTe₄ and Cu₃MSe₄ (M = V, Nb, Ta) can reach up to 2.06, 2.22, 2.36 and 1.91, 2.35 and 2.03, respectively. It is suggested that high band-degeneracy near the valence band edge is the main physical source for the predicted excellent thermoelectric performance. Simultaneously, a smaller effective mass of holes than that of electrons also benefits the enhanced thermoelectric properties of these p-type materials.