Highly efficient thermoelectric converters based on metalloporphyrin nanotubes

Abstract

Novel devices based on porphyrin nanotubes may lead to a wide range of uses in electronic functionality and thermoelectric conversion. π-conjugated metallo-porphyrin nanotubes have been designed with a configuration of opposite charged porphyrin molecules, which leads to oscillatory bandgaps as a function of the diameter of the nanotube. We focus in this work on bottom-up porphyrin nanotubes, rather different from conventional carbon nanotubes, which makes them also favorable candidates for making precursors of nanotube devices. We exploited the asymmetric band gap feature to design configurations of stacked six-metalloporphyrin rings connected by butadiyne to form periodic nanotube structure with different metallic atoms (Zn, Fe, and Fe-Cl). The electronic transport properties encapsulated in the transmission coefficients show that these porphyrin nanotubes in the presence of Zn give step-like features at asymmetric locations relative to the Fermi energy (EF), which leads to huge enhancements of the thermoelectric performance. The highest values obtained for the thermopower, and the electronic figure of merit can also be obtained for many different positions of EF, which makes Zn-porphyrin nanotube an optimal candidate for designing novel thermoelectric devices.