Tunable spin electronic and thermoelectric properties in twisted triangulene π -dimer junctions

In this work, we investigate the electronic properties and thermoelectric performance of triangulene π-dimer junctions with the twist angle from 0° to 60° by using first-principles calculations in combination with a non-equilibrium Green's function method. It is found that the triangulene π-dimer can be transformed between nonmagnetic state and antiferromagnetic or ferromagnetic state by varying the twist angle. The reason is that the relative rotation between the monomers weakens the overlap of two single occupied molecular orbital. More importantly, our theoretical analysis shows that the ferromagnetic states of the triangulene π-dimer junctions at the twist angle of 20°, 30°, and 60° have outstanding thermoelectric performance. The corresponding ZT value is as high as around 6, which is mainly contributed from the spin splitting nature. This work is instructive to improve the thermoelectric properties of π-stacking molecular junctions or organic polymers.