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Title: Valence disproportionation of GeS in the PbS matrix forms Pb₅Ge₅S₁₂ inclusions with conduction band alignment leading to high n-type thermoelectric performance
Authors: Luo, Zhong-Zhen
Cai, Songting
Hao, Shiqiang
Bailey, Trevor P.
Xie, Hongyao
Slade, Tyler J.
Liu, Yukun
Luo, Yubo
Chen, Zixuan
Xu, Jianwei
Luo, Wenjun
Yu, Yan
Uher, Ctirad
Wolverton, Christopher
Dravid, Vinayak P.
Zou, Zhigang
Yan, Qingyu
Kanatzidis, Mercouri G.
Keywords: Engineering::Materials
Issue Date: 2022
Source: Luo, Z., Cai, S., Hao, S., Bailey, T. P., Xie, H., Slade, T. J., Liu, Y., Luo, Y., Chen, Z., Xu, J., Luo, W., Yu, Y., Uher, C., Wolverton, C., Dravid, V. P., Zou, Z., Yan, Q. & Kanatzidis, M. G. (2022). Valence disproportionation of GeS in the PbS matrix forms Pb₅Ge₅S₁₂ inclusions with conduction band alignment leading to high n-type thermoelectric performance. Journal of the American Chemical Society, 144(16), 7402-7413.
Project: MOE 2018-T2-1-010 
Journal: Journal of the American Chemical Society
Abstract: Converting waste heat into useful electricity using solid-state thermoelectrics has a potential for enormous global energy savings. Lead chalcogenides are among the most prominent thermoelectric materials, whose performance decreases with an increase in chalcogen amounts (e.g., PbTe > PbSe > PbS). Herein, we demonstrate the simultaneous optimization of the electrical and thermal transport properties of PbS-based compounds by alloying with GeS. The addition of GeS triggers a complex cascade of beneficial events as follows: Ge2+ substitution in Pb2+ and discordant off-center behavior; formation of Pb5Ge5S12 as stable second-phase inclusions through valence disproportionation of Ge2+ to Ge0 and Ge4+. PbS and Pb5Ge5S12 exhibit good conduction band energy alignment that preserves the high electron mobility; the formation of Pb5Ge5S12 increases the electron carrier concentration by introducing S vacancies. Sb doping as the electron donor produces a large power factor and low lattice thermal conductivity (κlat) of ∼0.61 W m-1 K-1. The highest performance was obtained for the 14% GeS-alloyed samples, which exhibited an increased room-temperature electron mobility of ∼121 cm2 V-1 s-1 for 3 × 1019 cm-3 carrier density and a ZT of 1.32 at 923 K. This is ∼55% greater than the corresponding Sb-doped PbS sample and is one of the highest reported for the n-type PbS system. Moreover, the average ZT (ZTavg) of ∼0.76 from 400 to 923 K is the highest for PbS-based systems.
ISSN: 0002-7863
DOI: 10.1021/jacs.2c01706
Schools: School of Materials Science and Engineering 
Rights: © 2022 American Chemical Society. All rights reserved.
Fulltext Permission: none
Fulltext Availability: No Fulltext
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