Highly charged interface trap states in PbS_1–x govern electro-thermal transport

Journal Article · 16 July 2019 · APL Materials

DOI: https://doi.org/10.1063/1.5096786 · OSTI ID:1570619

Yazdani, Sajad  ^[1]; Huan, Tran Doan ^[2]; Liu, Yufei ^[3]; Kashfi-Sadabad, Raana  ^[1]; Montaño, Raul David ^[4]; He, Jian ^[3]; Pettes, Michael Thompson  ^[5]

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1. Univ. of Connecticut, Storrs, CT (United States)
2. Univ. of Connecticut, Storrs, CT (United States); Georgia Inst. of Technology, Atlanta, GA (United States)
3. Clemson Univ., SC (United States)
4. Univ. of Connecticut, Storrs, CT (United States); Univ. of Arizona, Tucson, AZ (United States)
5. Univ. of Connecticut, Storrs, CT (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Integrated Nanotechnologies (CINT)

This work describes our discovery of the dominant role of highly charged interfaces on the electrothermal transport properties of PbS, along with a method to reduce the barrier potential for charge carriers by an order of magnitude. High temperature thermoelectrics such as PbS are inevitably exposed to elevated temperatures during postsynthesis treatment as well as operation. However, we observed that as the material was heated, large concentrations of sulfur vacancy (V_$$\ddot{S}$$) sites were formed at temperatures as low as 266 °C. This loss of sulfur doped the PbS n-type and increased the carrier concentration, where these excess electrons were trapped and immobilized at interfacial defect sites in polycrystalline PbS with an abundance of grain boundaries. Sulfur deficient PbS_0.81 exhibited a large barrier potential for charge carriers of 0.352 eV, whereas annealing the material under a sulfur-rich environment prevented V_$$\ddot{S}$$ formation and lowered the barrier by an order of magnitude to 0.046 eV. Through ab initio calculations, the formation of V_$$\ddot{S}$$ was found to be more favorable on the surface compared to the bulk of the material with a 1.72 times lower formation energy barrier. Furthermore, these observations underline the importance of controlling interface-vacancy effects in the preparation of bulk materials comprised of nanoscale constituents.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); UConn Research Foundation
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1570619
• Report Number(s): LA-UR--18-31330
• Journal Information: APL Materials, Journal Name: APL Materials Journal Issue: 7 Vol. 7; ISSN 2166-532X
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English