Mechanical, optical, and thermoelectric properties of semiconducting ZnIn2X4 (X= S, Se, Te) monolayers

TL;DR

This study investigates the mechanical, optical, and thermoelectric properties of ZnIn2X4 monolayers, revealing their potential for energy conversion and optoelectronic applications due to their stability, low thermal conductivity, and favorable electronic properties.

Contribution

The paper provides a comprehensive analysis of ZnIn2X4 monolayers' properties, including mechanical stability, optical exciton behavior, and thermoelectric performance, highlighting their suitability for energy and optoelectronic devices.

Findings

ZnIn2S4 and ZnIn2Se4 are direct band gap semiconductors.

ZnIn2Te4 exhibits an indirect band gap of 1.84 eV.

Low lattice thermal conductivities suggest high thermoelectric efficiency.

Abstract

Mechanical stability of the ZnIn2X4 monolayers. The ZnIn2S4 and ZnIn2Se4 are semiconductors with direct band gaps of 3.94 and 2.77 eV, respectively whereas the ZnIn2Te4 shows an indirect band gap of 1.84 eV at the G0W0 level. The optical properties achieved from the solution of the Bethe-Salpeter equation predict the exciton binding energy of the ZnIn2S4, ZnIn2Se4, and ZnIn2Te4 monolayers to be 0.51, 0.41, and 0.34 eV, respectively, suggesting the high stability of the excitonic states against thermal dissociation. Using the iterative solutions of the Boltzmann transport equation accelerated by machine learning interatomic potentials, the room-temperature lattice thermal conductivity of the ZnIn2S4, ZnIn2Se4, and ZnIn2Te4 monolayers is predicted to be remarkably low as 5.8, 2.0, and 0.4 W/mK, respectively. Due to the low lattice thermal conductivity, high thermopower, and large figure of merit, we propose the ZnIn2Se4 and ZnIn2Te4 monolayers as promising candidates for thermoelectric energy conversion systems. This study provides an extensive vision concerning the intrinsic physical properties of the ZnIn2X4 nanosheets and highlights their characteristics for energy conversion and optoelectronics applications.