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Doping is known as an effective way to modify both electrical and thermal transport properties of thermoelectric alloys to enhance their energy conversion efficiency. In this project, we report the effect of Pd doping on the electrical and thermal properties of n-type Cu0.008Bi2Te2.7Se0.3 alloys. Pd doping was found to increase the electrical conductivity along with the electron carrier concentration. As a result, the effective mass and power factors also increased upon the Pd doping. While the bipolar thermal conductivity was reduced with the Pd doping due to the increased carrier concentration, the contribution of Pd to point defect phonon scattering on the lattice thermal conductivity was found to be very small. Consequently, Pd doping resulted in an enhanced thermoelectric figure of merit, zT, at a high temperature, due to the enhanced power factor and the reduced bipolar thermal conductivity. [ABSTRACT FROM AUTHOR]

We herein report an enhancement of the thermoelectric performance of spark plasma sintered polycrystalline n -type Bi 2 Te 2.7 Se 0.3 by the intercalation of Cu and the doping of Al on Bi-sites. Through the intercalation of a small amount of Cu (0.008), the reproducibility could be significantly improved, with ZT was enhanced from 0.64 to 0.73 at 300 K due to the reduced lattice thermal conductivity benefiting from intensified point-defect phonon scattering. We also found that Al is an effective doping element for power factor enhancement and for reducing the lattice thermal conductivity of Cu-intercalated Bi 2 Te 2.7 Se 0.3 . With these synergetic effects, an enhanced ZT values of 0.78 at 300 K and 0.81 at 360 K were obtained in 1 at% Al-doped Cu 0.008 Bi 2 Te 2.7 Se 0.3 (Cu 0.008 Bi 1.98 Al 0.02 Te 2.7 Se 0.3 ). [ABSTRACT FROM AUTHOR]

• SnSe 2- x Br x with x = 0, 0.004, 0.008, 0.01, and 0.02 were synthesized. • The valley degeneracy at conduction band minimum is increased by the Br doping. • The conduction band minimum also becomes flatter by the Br doping. • Power factor increased by increase in both carrier concentration and mobility. • Consequently, a thermoelectric figure of merit gradually improved with Br doping. [Display omitted] The effect of Br substitution on enhancing the thermoelectric properties of n -type layered SnSe 2 is investigated characterizing SnSe 2- x Br x synthesized with various Br contents (x = 0, 0.004, 0.008, 0.01, and 0.02). The electrical conductivity systematically increases with an increase in x owing to the simultaneous increase in both the carrier concentration (n) and mobility. As x increases, n increases by ~100 times; however, the magnitude of the Seebeck coefficient (| S|) decreases from 600 to 229 μV/K, resulting in an enhanced power factor at room temperature. The density functional theory calculations support that the valley degeneracy at the conduction band minimum increases with the Br substitution in SnSe 2 , while the conduction band minimum becomes flatter. This finding indicates that the increased density-of-state effective mass leads to the relatively large | S | even under a considerably increased n. Combined with the slight decrease in the thermal conductivity with an increase in x without significant additional phonon scattering, a thermoelectric figure of merit (zT) of 0.62 at 750 K is obtained for SnSe 1.98 Br 0.02 (x = 0.02), which is 50% higher than that for non-doped SnSe 2. [ABSTRACT FROM AUTHOR]