6H-[1,2,5]Thiadiazolo[3,4-e]thieno[3,2-b]indole-flanked para-azaquinodimethane based aromatic-quinoidal polymer semiconductors with high molecular weights synthesized via direct arylation polycondensation

The 6H-[1,2,5]thiadiazolo[3,4-e]thieno[3,2-b]indole-flanked para-azaquinodimethane (p-AQM)-based polymer semiconductors PQ-1 and PQ-2 are rationally designed through a p-extended aromatic-quinoidal design strategy. They are synthesized by the direct arylation polycondensation (DArP) method. Their physicochemical properties are investigated. Both polymers show high number-average molecular weights of over 120 kDa. PQ-1 exhibits a narrower band gap compared to its thiophene-flanked p-AQM polymer counterpart. PQ-2, with more aromatic thiophene units in the conjugated main chains, displays a broader band gap compared to PQ-1. Both PQ-1 and PQ-2 possess high-lying highest occupied molecular orbital energy levels (about -5.0 eV). They exhibit typical p-type semiconductor characteristics according to the results of characterization of organic field-effect transistors. This work presents an alternative p-extended aromatic-quinoidal design strategy and a convenient DArP method to build new p-AQM polymer semiconductors.