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

Abstract

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.

Publication Date:

2019-07-16

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1570619

Alternate Identifier(s):

OSTI ID: 1542685

Report Number(s):

LA-UR-18-31330
Journal ID: ISSN 2166-532X

Grant/Contract Number:  

89233218CNA000001

Resource Type:

Accepted Manuscript

Journal Name:

APL Materials

Additional Journal Information:

Journal Volume: 7; Journal Issue: 7; Journal ID: ISSN 2166-532X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Material Science; Semiconductors; Polycrystalline material; Interfaces; Thermoelectrics; Potential energy barrier; Transport properties; Crystallographic defects; Thermal transport; Ab-initio methods