First Principle Investigation on Thermoelectric Properties of Transition Metal Dichalcogenides: Beyond the Rigid Band Model

The thermoelectric properties (electrical conductivity, Seebeck coefficient, and power factor) of single layer transition metal dichalcogenides (MoS2, MoSe2, WS2, and WSe2) are investigated theoretically on the basis of ab initio quantum transport using the Landauer Buttiker formalism. The often used rigid band model is compared to realistic doping, namely substitution and adsorption, it is found that several important physical insights governing the transport are missing in this approximation. The rigid band model appears to clearly overestimate the thermoelectic efficiency, hampering its relevance for thermoelectric studies. Substitution doping by chloride or phosphorus leads to poor power factor due to drastic changes of the pristine band structure. In contrast, adsorption doping by alkalies (Li, Na, K, and Rb) favors larger power factor. Realistic treatment of the disorder induced by the dopants is also investigated and reveals that Cl doping leads to very short localization length of 3.5 nm while K c...