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Enhancement of Thermoelectric Performance for n-Type PbS through Synergy of Gap State and Fermi Level Pinning
- Luo, Zhong-Zhen, Hao, Shiqiang, Cai, Songting, Bailey, Trevor P., Tan, Gangjian, Luo, Yubo, Spanopoulos, Ioannis, Uher, Ctirad, Wolverton, Chris, Dravid, Vinayak P., Yan, Qingyu, Kanatzidis, Mercouri G.
- Journal of the American Chemical Society 2019 v.141 no.15 pp. 6403-6412
- ambient temperature, gallium
- We report that Ga-doped and Ga–In-codoped n-type PbS samples show excellent thermoelectric performance in the intermediate temperature range. First-principles electronic structure calculations reveal that Ga doping can cause Fermi level pinning in PbS by introducing a gap state between the conduction and valence bands. Furthermore, Ga–In codoping introduces an extra conduction band. These added electronic features lead to high electron mobilities up to μH ∼ 630 cm² V–¹ s–¹ for n of 1.67 × 10¹⁹ cm–³ and significantly enhanced Seebeck coefficients in PbS. Consequently, we obtained a maximum power factor of ∼32 μW cm–¹ K–² at 300 K for Pb₀.₉₈₇₅Ga₀.₀₁₂₅S, which is the highest reported for PbS-based systems giving a room-temperature figure of merit, ZT, of ∼0.35 and ∼0.82 at 923 K. For the codoped Pb₀.₉₈₆₅Ga₀.₀₁₂₅In₀.₀₀₁S, the maximum ZT rises to ∼1.0 at 923 K and achieves a record-high average ZT (ZTₐᵥg) of ∼0.74 in the temperature range of 400–923 K.