Leveraging Deep Levels in Narrow Bandgap Bi_0.5Sb_1.5Te₃ for Record‐High zT_ave Near Room Temperature

Abstract

Deep levels in a narrow bandgap semiconductors are considered detrimental to their electrical performance. Here the constructive role of Indium-induced deep levels in regulating the majority and minority carriers for state-of-theart average thermoelectric figure-of-merit zT ave between 300 and 500 K in narrow bandgap p-type (Bi,Sb) 2 Te 3 is reported. Two compositional series in the pseudo-ternary Bi 2 Te 3-Sb 2 Te 3-In 2 Te 3 phase diagram: Bi 0.475−x Sb 1.525 In x Te 3 (0 ≤ x ≤ 0.15) and Bi 0.475 Sb 1.525−y In y Te 3 (0 ≤ y ≤ 0.10), namely, the x-series and y-series are explored. In the x-series, the combined experimental and theoretical study shows that Indium doping induced donor-like and acceptor-like deep levels, enlarges the band gap, and flattens the conduction band edge, thereby weakening the temperature dependence of Seebeck coefficient and the bipolar heat conduction. Further doping the x-series with copper (aka shallow acceptors) to optimize the majority carrier concentration leads to a state-of-the-art zT ≈ 1.61 at 390 K and record-high average zT ave ≈ 1.47 between 300 and 500 K in p-type Bi 0.396 Sb 1.525 In 0.075 Cu 0.004 Te 3. These results attest to the efficacy of deep levels in narrow bandgap thermoelectrics for both power generation and solid-state refrigeration near room temperature.

Electronic Topological Transition as a Route to Improve Thermoelectric Performance in Bi0.5Sb1.5Te3

“…To better highlight the advantages, we have compared our result with the representative p‐type Bi 0.5 Sb 1.5 Te 3 materials are shown in Figure 6b. [ 8,20,22,25–27,54–56 ] Clearly, the zT value of our Bi 0.5 Sb 1.5 Te 3 material at 300 K outperforms almost all the best reported materials and is comparable even to the best reported by Kim et al. [ 20 ] The pressure‐driven ETT turns out to be an effective way to tune the electronic structure for the improved TE properties while maintaining the same crystal structure.…”

“…b) The comparison of our obtained peak zT at room temperature with the other high‐ zT p‐type Bi 0.5 Sb 1.5 Te 3 materials. [ 8,20 ] [ 22,25–27 ] [ 54–56 ]…”

(Bi,Sb)2Te3/SiC nanocomposites with enhanced thermoelectric performance: Effect of SiC nanoparticle size and compositional modulation

“…Intuitively, nanoparticles with an appropriate size should have a stronger and more beneficial effect on the TE performance. On the other hand, because the TE properties are sensitive to material compositions [31,32], a fixed matrix composition is favorable for investigating the effect of the nanoparticle size on the TE properties. SiC has a wide band gap and low cost, and ultrafine SiC particles can be easily obtained.…”

Lower thermal conductivity of body centered cubic carbon (C14): a comparative study with diamond

“…Carbon materials had been well known to display various kinds of superior properties, making them suitable for designing conductive devices, [1][2][3][4][5][6][7][8][9] especially decorated with suitable transition-metal based or oxygen-containing clusters. [10][11][12][13][14][15][16][17][18][19][20] The special electronic structure of carbon atoms enables them to form all kinds of crystal structures via different hybrid bonding states, like sp 3 , sp 2 , and sp. Within the last few decades, a variety of carbon allotropes, like diamond, graphene, carbon nanotubes, and fullerenes, had been successfully synthesized, and due to their specific functionalities and structural features, they had been applied as important preparation materials.…”