Thermoelectric performance of porphyrin molecular junction with graphene nanoribbon electrodes

Abstract

Thermoelectric performance of porphyrin molecular junction is investigated by using first-principles calculation combined with nonequilibrium Green function (NEGF) method. It is found that porphyrin molecule rotation (90[Formula: see text] rotated) has no obvious effect on its thermoelectric conversion efficiency due to the conjugate structure of central molecule. Through the functions of energy and thermal conductivity, it is found that phonon thermal conductivity accounts for the main part, which provides a potential for further optimizing thermoelectric performance. Moreover, it can be seen from phonon transmission spectrum that porphyrin molecule has a certain filtering effect on high-frequency phonon mode. For power factor and figure of merit (ZT), wave functions for two cases highly coincide. The maximum ZT values of por1 and por2 are 0.38 and 0.34 near Fermi level (FL), respectively. Porphyrin molecular junction could have a good application prospect in nanoscale thermoelectric devices.