Prediction of structurally stable two-dimensional AuClO2 with high thermoelectric performance

Abstract

Numerous two-dimensional (2D) materials have been reported to exhibit remarkable thermoelectric (TE) performances owing to their quantum confinement effects. However, the identification of ideal TE materials with a low thermal conductivity (κ_L) and high Seebeck coefficient (|S|) remains a formidable challenge due to their high coupling and inherent conflict. In this work, a new monolayer semiconductor AuClO₂ with a balanced TE performance has been theoretically predicted by combining first-principles calculations with the Boltzmann transport equation. The results of phonon spectrum, molecular dynamic (MD) simulations, and mechanical property analyses suggest that AuClO₂ features thermodynamic and mechanical stability. Strikingly, AuClO₂ possesses an ultralow κ_L of 0.14 (0.45) W m⁻¹ K⁻¹ along the a (b)-axis at 300 K, thanks to its low phonon group velocity (υ_ph) and short phonon lifetime (τ_ph). Furthermore, the flat valence bands of AuClO₂ promote a high |S| under p-type doping, leading to large zT values in the range of 1.0–2.4 under different temperatures and even up to a maximum value of 2.35 at 900 K. This study offers a promising TE material for applications in fields such as thermal insulation and thermoelectric refrigeration, and provides theoretical guidelines for the design of high performance 2D TE materials.