Valence Disproportionation of GeS in the PbS Matrix Forms Pb5Ge5S12Inclusions with Conduction Band Alignment Leading to High n-Type Thermoelectric Performance

Zhong Zhen Luo, Songting Cai, Shiqiang Hao, Trevor P. Bailey, Hongyao Xie, Tyler J. Slade, Yukun Liu, Yubo Luo, Zixuan Chen, Jianwei Xu, Wenjun Luo, Yan Yu, Ctirad Uher, Christopher Wolverton, Vinayak P. Dravid, Zhigang Zou*, Qingyu Yan, Mercouri G. Kanatzidis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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 Pb5Ge5S12as stable second-phase inclusions through valence disproportionation of Ge2+to Ge0and Ge4+. PbS and Pb5Ge5S12exhibit good conduction band energy alignment that preserves the high electron mobility; the formation of Pb5Ge5S12increases 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-1K-1. The highest performance was obtained for the 14% GeS-alloyed samples, which exhibited an increased room-temperature electron mobility of ∼121 cm2V-1s-1for 3 × 1019cm-3carrier 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.

Original languageEnglish (US)
Pages (from-to)7402-7413
Number of pages12
JournalJournal of the American Chemical Society
Volume144
Issue number16
DOIs
StatePublished - Apr 27 2022

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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