Optimized Mn and Bi co-doping in SnTe based thermoelectric material: A case of band engineering and density of states tuning

Improving the ZT of SnTe using electronic structure engineering: unusual behavior of Bi dopant in the presence of Pb as a co-dopant

“…11 While several previous reports of Bi doping in SnTe have indicated that there is no decrease in the energy offset of valence sub-bands by the addition of Bi, herein we see that co-doping it with Pb decreases the energy offset value to 0.173 eV. 21,22,28 This unusual behavior of Bi is seen only in the presence of Pb highlighting the importance of choosing right combination of dopants for engineering the electronic structure. 21,22 Similar to the valence sub-bands, light and heavy hole conduction sub-bands at Γ point and Z+δ in Z→R direction, respectively have large energy offset in SnTe compared to GeTe.…”

“…26,27 We know that Bi is a n-type resonant dopant in SnTe known to introduce resonance levels just beneath the conduction band and improve the room temperature Seebeck co-efficient. 21,22,28 Hence, we co-doped Bi to beneficially tune the electronic structure. In the electronic structure of Pb-Bi co-doped SnTe, we observe an increase of 0.147 eV in the band gap at Γ point, effectively solving the problem of bipolar effect (Figure 1c).…”

Vanadium: A Protean Dopant in SnTe for Augmenting Its Thermoelectric Performance

“…Electrons in real space undergo such strong localization, which leads to such appearances in momentum space. 39 Such a combination of highly dispersive and flat bands is reported previously to yield multiple Fermi surfaces and potentially boost the Seebeck coefficient. 40 The eightfold degenerate conduction band (L CB ) here splits into four sets of doubly degenerate bands with the lower 3 sets forming the resonance band (forming the conduction valley CB V1 at the Γ point) and the fourth set (indicated as CB V2 in Figure 2) remaining 0.198 eV above the resonance level.…”

Molybdenum as a versatile dopant in SnTe: a promising material for thermoelectric application

“…Bi, In, Zn, V and Mn are known to introduce resonance levels in SnTe. [20][21][22][23][24] A record high room temperature ZT of 0.3 (@ 300 K) for lead free SnTe was reported by co-doping SnTe with Bi and Zn resonant dopants. 24 To decrease the thermal conductivity, the dopants like Cu, Sb and Pb are known to be very effective.…”

“…2,[25][26][27][28][29] Co and multi-doping of elements are also implemented to synergistically extract different benefits and increase the ZT for a broad range of temperature. 2,12,13,16,20,[23][24][25][26][27][28][29][30][31] Although resonant dopants improve the 'S' value, they decrease the 'σ' due to carrier scattering and decreased mobility and hence exhibit poor power factor values. 32 Many of the currently implemented techniques are good at improving the high temperature power factor leading to a record value of ~47 μW/cmK 2 in SnTe co-doped with Ca and resonant dopant In, but have poor values at room temperature.…”