Effects of Molecular Combination and Side Groups for Thiophene-Benzene-Based Nanodevices

The electron transport properties of thiophene-benzene-based molecules attached to zigzag graphene nanoribbon (ZGNR) electrodes are investigated using density functional theory and the nonequilibrium Green function. The results show that 3,6-(dithiophen-2-yl)benzene has better performance compared to 2,5-diphenylthiophene. Interestingly, both the devices exhibit two negative differential resistance (NDR) peaks while a thiophene or a benzene molecule tethered to ZGNR electrodes shows one NDR peak. Although the side groups −OH, −NO2, and −NH2 controllably repress the transmission and current of 3,6-(dithiophen-2-yl)benzene, the current rectification performance is found because of its asymmetry of molecule structure. Unexpectedly, 2,5-diphenylthiophene system added by a thiophene shows semiconductor behavior under a certain bias region. These results contribute to a deep understanding of the electron transport properties of molecular combination and are valuable for designing molecular devices with excellent and distinctive performance at nanoscale.