Significantly Enhanced Thermoelectric Performance via Excitons in Bilayer Transition-Metal Dichalcogenides

Transition metal dichalcogenides (TMDCs) and other nanoscale materials, characterized by their layered structure and high electron and hole mobility, present promising opportunities for high-performance transistors and electronic devices. In this work, we propose a novel two-dimensional π-junction nanostructure, comprising two layers of doping MoS2​ with indirect excitons, for thermoelectric applications. Indirect excitons, with their high binding energy, exhibit enhanced resistance to scattering, leading to significantly longer relaxation times. Their bosonic nature further facilitates more efficient transport compared to single carriers. We develop a theoretical model and perform numerical simulations based on first-principles calculations and experimental data. Our findings show that indirect excitons can simultaneously improve the Seebeck coefficient and electrical conductivity while reducing the Lorenz number. The high exciton thermal conductivity also compensates for the inherently high lattice thermal conductivity in TMDCs. Consequently, the device's figure of merit (zT) and power factor demonstrate an order of magnitude enhancement over those observed in decoupled layers.