Novel p-type thermoelectric materials Cu3MCh4 (M = V, Nb, Ta; Ch = Se, Te): High band degeneracy
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 structures to HH alloys. The electronic and thermal transport properties of these materials are quantitatively evaluated using the 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, 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 lighter effective mass of holes than that of electrons also benefits to the enhanced thermoelectric properties of these p-type materials.