First-principles study of side groups effects on the electronic transport in conjugated molecular device

By applying first-principles quantum transport calculations, we investigate the transport properties of the oligo(p-phenylenevinylene)s molecular devices modulated with different side groups. The calculated results show that for the system modulated with –NH2–NH2, the highest occupied molecular orbital is localized, while for the system modulated with –NO2–NO2, the lowest unoccupied molecular orbital is localized. The electron transport will be enhanced when modulated only with –NH2–NH2 or –NO2–NO2, but will be weakened when modulated with both –NH2–NH2 and –NO2–NO2. Negative differential resistance is observed in the system modulated with two –NH2–NH2. A mechanism for the negative differential resistance behavior is suggested.