Discovery of high thermoelectric performance of WS2-WSe2 nanoribbons with superlattice and Janus structures

Abstract

Transition metal dichalcogenide monolayers have shown enormous potential in thermoelectric application in recent years. We now focus on the thermoelectric properties of WS2-WSe2 nanoribbons with superlattice (SL) and Janus (JA) structures using first-principles calculations. The WS2, WSe2, SL, and JA nanoribbons with the ribbon width from 5 to 7 have high structural stabilities. All nanoribbon electronic structures are semiconductors and the ribbon width will modify bandgaps. It can be also observed that WS2, SL, and JA nanoribbons with a ribbon width of 5 have the largest carrier mobilities (up to ~500–1400 cm2 V−1 s−1) and relaxation times (up to ~400–600 fs). We further calculate the electronic transport coefficients and discover that the SL and JA nanoribbons with a ribbon width of 5 exhibit the largest power factors as high as ~80 mW m−1 K−2. Afterwards, the minimum lattice thermal conductivities of SL and JA nanoribbons are 0.53 W m−1 K−1 and 0.61 W m−1 K−1, which are suppressed owing to the declining phonon group velocity and phonon lifetime. The maximum ZT values of SL and JA nanoribbons can reach 5.47 and 4.13. This investigation provides a solid evidence for the application of WS2-WSe2 nanoribbons as promising thermoelectric materials.