Electron-vibration effects on the thermoelectric efficiency of molecular junctions

The thermoelectric properties of a molecular junction model, appropriate for large molecules such as fullerenes, are studied within a nonequilibrium adiabatic approach in the linear regime at room temperature. A self-consistent calculation is implemented for electron and phonon thermal conductance showing that both increase with the inclusion of the electron-vibration coupling. Moreover, we show that the deviations from the Wiedemann-Franz law are progressively reduced upon increasing the interaction between electronic and vibrational degrees of freedom. Consequently, the junction thermoelectric efficiency is substantially reduced by the electron-vibration coupling. Even so, we find that, for realistic parameters values, the thermoelectric figure of merit can still have peaks of the order of unity.