Optimizing the conductance switching performance in photoswitchable dimethyldihydropyrene/cyclophanediene single-molecule junctions

Abstract

Designing molecular switches with high stability and performance is still a great challenge in the field of molecular electronics. For this aim, key factors influencing the charge transport properties of molecular devices require to be carefully addressed. Here, by using the nonequilibrium Green's function method in combination with the density functional theory, effect of bridging manner (i.e., linkage sites) for dimethyldihydropyrene (DHP)/cyclophanediene (CPD) photoswitchable molecule sandwiched between two Au(111) electrodes has been theoretically investigated. The computational results show that the fully conjugated DHP is more conductive than the less conjugated CPD, manifesting an evident switching effect. It is also found that the ON/OFF switching performance of DHP/CPD is dramatically modulated by the bridging manner. Further analysis attributes the switching feature to the different alignments of conducting HOMO with the Fermi energy for DHP and CPD. And it also reveals that local bond contributions to the electron transmission pathway are closely related to both the conjugation characteristics and bridging manner of the core molecule. This work suggests that the bridging manner of core molecule in single-molecule junction plays an essential role in determining the switching performance and should be carefully addressed in future design of molecular switches.