Ultrahigh thermoelectric performance of Janus α-STe2 and α-SeTe2 monolayers

• Published in: Physical chemistry chemical physics : PCCP 2022-11, Vol.24 (46), p.28295-28305
• Main Authors: Liu, Gang, Guo, Aiqing, Cao, Fengli, Ju, Weiwei, Wang, Zhaowu, Wang, Hui, Guo-Ling, Li, Gao, Zhibin
• Format: Article
• Language: English
• Subjects: Anharmonicity; Conductivity; Figure of merit; First principles; Heat conductivity; Heat transfer; Monolayers; Thermal conductivity; Thermoelectric materials; Transport theory
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d2cp03659b

Janus α-STe2 and α-SeTe2 monolayers are investigated systematically using first-principles calculations combined with semiclassical Boltzmann transport theory. Janus α-STe2 and α-SeTe2 monolayers are indirect semiconductors with band gaps of 1.20 and 0.96 eV, respectively. It is found that they possess ultrahigh figure of merit (ZT) values of 3.9 and 4.4, respectively, at 500 K, much higher than that of the pristine α-Te monolayer (2.8). The higher ZT values originating from Janus structures reduce lattice thermal conductivities remarkably compared with the pristine α-Te monolayer. The much higher phonon anharmonicity in Janus monolayers leads to significantly lower lattice thermal conductivity. It is also found that electronic thermal conductivity can play an important role in thermoelectric efficiency of materials with quite low lattice thermal conductivity. This work suggests the potential applications of Janus α-STe2 and α-SeTe2 monolayers as thermoelectric materials and highlights that using a Janus structure is an effective way to enhance thermoelectric performance.