Investigation of Electric and Thermoelectric Properties of Phthalocyanine monomer/dimer Molecular Junctions

Abstract

Abstract In this work, we carried out a theoretical calculation to present the electrical and thermoelectrical properties of five monomers/dimers structures based on Phthalocyanine molecule sandwiched between gold electrodes. The calculation was preformed based on density functional theory (DFT) implemented by SIESTA. The results reveal that the transmission calculations T(E) of all five monomers/dimers show no spin dependent with highest value for monomer structure around Fermi energy. The phthalocyanine monomer structures show higher conductivity calculation around the Fermi energy in comparison to conductivity values of phthalocyanine dimer structures. Further, thermoelectric properties such as Seebeck coefficient (S), thermal conductance (k) and figure of merit (ZT) are also presented. It is found that the highest positive Seebeck coefficient (S) value belongs to zinc phthalocyanine monomer, while the highest negative (S) value belongs to free base phthalocyanine dimer structure over a wide range of Fermi energies. Moreover, zinc phthalocyanine monomer structure shows highest thermal conductance (k), while phthalocyanine dimer structures exhibit lowest thermal conductance (k) in the vicinity of DFT predicted Fermi energy. As a result, high room-temperature figure of merit (ZT ≈1.7) is reported for free base phthalocyanine dimer, which might be due to the low thermal conductivity and high Seebeck coefficient and electrical conductance values, which makes it a preferred candidate for potential thermoelectric applications.