2d Single-Layer Pi-Conjugated Nickel Bis(Dithiolene) Complex: A Good-Electron-Poor-Phonon Thermoelectric Material

Recently, the 2D dt planar sr-conjugated transition metal complexes have gained extensive attention owing to their extra-high electrical conductivity. Meanwhile, low lattice thermal conductivities can be expected for their soft and microporous structures, suggesting very promising thermoelectric applications. Herein, based on first-principles calculations and molecular dynamics simulations, it is identified that monolayered 2D nickel bis(dithiolene) complex, (NiC4S4)(n), is indeed such a material that exhibits exceptionally high electron mobility, low lattice thermal conductivity, and thereby excellent thermoelectric performance. The calculated figure of merit at 300 K can reach up to 0.92 for a perfect nanosheet. At the same time, the mechanism behind is uncovered, that is, the weak electron-acoustic phonon coupling allowing high electron mobility, and its microporous structure decreasing the thermal transport. The surprisingly weak electron acoustic -phonon coupling arises from mixed bonding antibonding nature of conduction band. The finding opens a new opportunity for these 2D coordination complexes as potential thermoelectric materials.