Functional oligothiophenes as advanced molecular electronic materials

The oligothiophene/fullerene dyad system shows marked photoinduced electron transfer from the oligomer to the attached fullerene at the terminal position, and is successfully put to practical use in the fabrication of photovoltaic cells. The further modified dyad system, attaching a thiol or disulfide anchoring group at another terminal position, can form a self-assembled monolayer (SAM) on a gold substrate, where the tethered molecules are unidirectionally ordered. In particular, the use of a tripodal anchoring group provides a powerful approach for the formation of a much denser and more stable SAM, which is beneficial for the high performance of SAM-based photovoltaic cells. The porphyrin/oligothiophene/fullerene triad system is designed to evaluate efficient intramolecular electron transfer from the terminal porphyrin to the other terminal fullerene through the central oligothiophene, revealing the high potential of oligothiophene as a long-range molecular wire. Other oligothiophenes incorporating pyrenes or terpyridines are developed as light-emitting materials useful for electroluminescent (EL) devices. In these devices, the pyrene-modified system also acts as a hole-transport layer, whereas the terpyridine-modified system acts as an electron-transport layer.