Thermoelectric Properties of Cu2SnSe4 with Intrinsic Vacancy

Phonon scattering by point defects has been proven as an effective strategy for thermoelectric performance enhancements through reducing lattice thermal conductivity. This type of scattering largely relies on the mass and strain fluctuations between host and guest atoms, both of which can be maximized by vacancies as demonstrated in a few thermoelectric solid solutions showing a significant reduction in the lattice thermal conductivity. Here we show Cu 2 SnSe 4, a new compound with intrinsic vacancies on the cation site, as a promising thermoelectric material due to the low lattice thermal conductivity of 0.6 W m –1 K –1 intrinsically resulting from the vacancies. A peak thermoelectric figure of merit ( zT ) of ∼0.6 is achievable in this compound without relying on additional approaches such as nanostructuring or band engineering. This result demonstrates the existence of intrinsic vacancies as an important guidance for exploring new thermoelectric materials.