Thermoelectric performance strain regulation based on boron/nitrogen-doped triangular graphene dimer molecules

The development of new thermoelectric functional materials and the quantum regulation of the thermoelectric conversion efficiency of nanodevices have become key measures in the strategic layout of new energy. In this paper, density functional theory combined with non-equilibrium Green’s function method is used to systematically study thermoelectric conversion properties of boron/nitrogen-doped triangular graphene dimer molecular junctions. The results show that boron atom doping can effectively stretch the C-B bond length, reduce the central molecular orbital energy level, and optimize the matching degree between the central molecular orbital energy level and the Fermi level of electrode, leading to promote electron transport behavior of the molecular device at the Fermi level. Due to boron/nitrogen (electron-deficient/electron-rich) atom doping, the central molecular distance of triangular graphene dimer is significantly strained, and the molecular interface barrier surges, resulting in very low phonon thermal conductance of the boron/nitrogen-doped molecular junction devices compared with other two molecular junctions. Combined with the mutual restraint of conductance and thermal conductance, the boron-doped molecular junction obtains the maximum value of 0.0044 at the Fermi level, which is about 10 times that of boron/nitrogen-doped system. This work has important theoretical guidance for design rich/deficient electron doping and construction of high-quality thermoelectric molecular junctions.