Structural Arrangement and Improved Thermoelectric Figure of Merit in Hexagonal MoXY (X = S, Se, Te; Y = Se, Te, O) Monolayers: Understanding from First-Principles Calculations

Thermoelectric (TE) materials with efficiencies comparable to Carnot efficiency are highly desirable for applications in devices that utilize the TE effect to convert heat into electricity. The efficiency of a TE material is measured by its figure of merit, which is influenced by the complex interplay between electronic and thermal transport parameters. Janus materials, with their large specific surface area, can enhance the movement of electrons and holes generated by heat towards the reaction interface. One example of a two-dimensional (2D) transition metal dichalcogenide used in this study is molybdenum-based materials. In this research, we investigated the electronic and thermoelectric properties of 2D Janus materials using first-principles electronic structure methods combined with semiclassical Boltzmann transport theory, calculating relaxation times using molybdenum-based materials and analyzing their impact on TE properties. We found that relaxation time calculations played a critical role in significantly altering transport phenomena, leading to a higher figure of merit and thus enhancing TE efficiency. This study is significant as it highlights the important structure-property relationship in determining TE efficiency, which could pave the way for the discovery of new TE materials with higher efficiencies. The results show that the thermoelectric properties of molybdenum-based materials indicate that MoSeO exhibits the highest maximum power factor (PF) across all temperatures. For p-type carriers in MoSeO, the PF reaches 32.568 mW/mK 2 at 900 K, while for n-type carriers, the maximum PF reaches 3.419 mW/mK 2 at the same temperature. These findings suggest that MoSeO has a high thermoelectric potential, particularly at high temperatures, making it a promising candidate for future thermoelectric applications.