Novel π-Conjugated Polymer Based on an Extended Thienoquinoid

With a fused terthiophene, dithieno[3,4-b:2′,3′-d]thiophene (DTT) is used as a thienoquinoidal building block for conjugated polymers. However, due to its highly extended heteroarene structure, chemical synthesis of the functional DTT unit is a challenge. All known DTT-based polymer films were prepared by an electrochemical polymerization approach. In this study, we first synthesized the functional DTT monomer and DTT-based conjugated polymer, PDBT-DTT, via a typical Stille coupling reaction. With another fused thiophene ring, DTT shows increased aromatic (weaker quinoid) character compared to the thieno-[3,4-b]thiophene (TT) unit. Moreover, PDBT-DTT showed much higher photovoltaic performance as well as better thermal and photostability than its TT-based analogue (PDBT-TT). The results demonstrate that DTT is a potential quinoidal building block for constructing high-performance conjugated polymers.