Precise Regulation of Carrier Concentration in Thermoelectric BiSbTe Alloys via Magnetic Doping

Abstract

The Bi 2 Te 3 -based alloy is the best commercial thermoelectric material around room temperature, although it is extremely difficult to further improve its thermoelectric performance. In this work, we demonstrate that magnetic doping is an effective strategy to regulate the thermoelectric performance of p-type Bi 0.5 Sb 1.5 Te 3 . According to our experiments, it is much more difficult for ferromagnetic Fe/Co to enter the Bi 0.5 Sb 1.5 Te 3 lattice in comparison with diamagnetic Pb, which can be understood by the "like dissolves like" rule. At the same doping content, Fe and Co provide much lower hole carriers than Pb due to their larger carrier thermal activation energies, indicating that Fe and Co as dopants are very applicable for the fine regulation of the carrier concentration. The Fe/Co-doped samples have higher Seebeck coefficients but less carrier mobilities than the Pb-doped sample since the doped magnetic atoms induce additional carrier scattering. Beyond the solid solubility limit, excess Fe/ Co represents as the impurity, which can maintain a high carrier concentration due to the metal−semiconductor contact. Finally, the zT values of ∼1.05 and 1.15 near room temperature have been achieved for the samples with 1.71 at. % Co and 1.80 at. % Fe, respectively.

Leveraging Deep Levels in Narrow Bandgap Bi0.5Sb1.5Te3 for Record‐High zTave Near Room Temperature

“…This is a recordhigh zT ave value reported for the p-type (Bi,Sb) 2 Te 3 material in view of both the thermal and electrical properties measured along the same direction (Figure 6f). [5,22,44,45,[47][48][49][50][51][52] One must measure all the TE properties and calculate the zT in the same direction to avoid over-estimation of zT. Otherwise, a zT value ≈ 2.0 would be obtained if the in-plane PF and the out-of-plane κ are used for the w = 0.004 sample (cf.…”

Optimizing Room-Temperature Thermoelectric Performance of n-Type Bi2Te2.7Se0.3

“…In recent years, Bi 2 Te 3 -based compounds have been widely commercialized as the best-performing room-temperature TE material. Bi 2 Te 3 -based compounds belong to the rhombohedral crystal system with the Te (1) –Bi–Te (2) –Bi–Te (1) atomic layer as the basic unit repeatedly arranged in the c -axis direction. , The interlayer is connected by covalent and ion bonds, while the adjacent layers are connected by a weak van der Waals force, leading to the facile cleavage along the in-plane direction. The special layered crystal structure allows the thermal and electrical properties of the Bi 2 Te 3 -based compounds to exhibit strong anisotropy in different directions. − Overall, the TE performance in the vertical hot pressing (HP) direction is higher than that in parallel to the HP direction.…”

Excellent Thermoelectric Performance from In Situ Reaction between Co Nanoparticles and BiSbTe Flexible Films

“…Te vacancies are introduced with the formation of CoTe 2 , which induces the migration of Bi to occupy the vacant Te according to eq , and then, holes are generated . The carrier concentration drops slightly when the Co-NPs content exceeds 0.2% because of the metal–semiconductor contact (Figure b). ,− The work function of Co-NPs (5.0 eV) is smaller than that of Bi 0.5 Sb 1.5 Te 3 (5.65 eV), which leads to a transfer of electrons from the Co-NPs to Bi 0.5 Sb 1.5 Te 3 and neutralizes part of holes, thus reducing the carrier concentration. The competition of the defect and charge-transfer effect results in a maximum carrier concentration at 0.2% Co-NP incorporation (Co02).…”