Thermoelectric properties of SbXY (X = Se, Te; Y = Br, I) Janus layers

TL;DR

This study investigates the thermoelectric properties of SbXY Janus layers, revealing their stability, low thermal conductivity, and promising figure of merit, especially in SbSeBr, for high-temperature thermoelectric applications.

Contribution

The paper provides a comprehensive first-principles analysis of SbXY Janus layers, highlighting their stability, anisotropic transport, and high thermoelectric performance, which was not previously characterized.

Findings

SbXY Janus layers are structurally stable up to 1000 K.

Thermal conductivity is suppressed in Br-containing layers.

SbSeBr achieves a figure of merit of 0.6 at 1000 K.

Abstract

We report a comprehensive investigation of the thermoelectric properties of SbXY (X = Se, Te; Y = Br, I) Janus layers (JL) using spin-polarized first-principles calculations. Ab initio molecular dynamics confirm that the 1T phase ($Pm31$) remains stable up to 1000 K, excluding any phase transitions. The calculated mean-square displacement further evidences the structural robustness. The thermal conductivity is strongly suppressed in Br-containing layers due to enhanced Froehlich interactions between optical and acoustic phonons. Electronic structure calculations reveal indirect band gaps of 1.1 to 1.3 eV, with valence and conduction bands dominated by the $p$-orbitals of halogen/chalcogen and of Sb, respectively. The carrier effective mass highlights anisotropic transport with lighter electrons being more mobile, while holes dominate the power factor, which attains values on the order of mW/mK$^2$. Direction-dependent transport indicates superior thermoelectric performance along the $xx$ direction, with negligible contribution along $yy$. The Figure of Merit reaches 0.6 at 1000 K in hole-doped SbSeBr, demonstrating strong potential for high-temperature applications. Our results reveal that the SbXY JLs, particularly SbSeBr, emerge as promising candidates for next-generation thermoelectric devices at elevated temperatures.