Theoretical Study of Intrinsic and Extrinsic Point Defects and Their Effects on Thermoelectric Properties of Cu 2 SnSe 3 .

Current understanding of the intrinsic point defects and potential extrinsic dopants in p-type CuSnSe is limited, which hinders further improvement of its thermoelectric performance. Here, we show that the dominant intrinsic defects in CuSnSe are Cu and V under different chemical conditions, respectively. The presence of V will damage the hole conduction network and reduce hole mobility. Besides, we find that the substitution of Al, Ga, In, Cd, Zn, Fe, and Mn for Sn can inhibit the formation of V; introducing Cu, Fe, Mn, and Ni defects can significantly enhance electronic density of states near the Fermi level due to the contribution of 3d orbitals. Therefore, increasing the Cu content and/or introducing the above beneficial dopants appropriately are expected to cause enhancement of carrier mobility and/or thermopower of CuSnSe. Furthermore, introducing Ag, Al, Zn, Ge, and Mn defects can induce large mass and strain field fluctuations, lowering lattice thermal conductivity remarkably. Present results not only deepen one's insights into point defects in CuSnSe but also provide us with a guide to improve its thermoelectric properties.