Synthesis of Two‐Dimensional Terbenzodithiophene‐based Derivative by Palladium‐catalyzed C─H Benzannulation and Its Donor–Acceptor Copolymers for Organic Photovoltaics

A two‐dimensional heptacyclic tetrathienyl‐TBDT (TBDT‐4T) was synthesized by palladium‐catalyzed C─H benzannulation. The stannlyated TBDT was copolymerized with FBT and FTT monomers to produce PTBDT‐FBT and PTBDT‐FTT with excellent thermal property and air stability. The inverted PSC devices using PTBDT‐FBT and PTBDT‐FTT showed a PCE of 4.16 and 3.98%, respectively. A new two‐dimensional tetrathienyl‐TBDT (TBDT‐4T) was synthesized by employing palladium‐catalyzed C─H benzannulation between an iodobiaryl and 1,2‐dithienylacetylene. The stannylated TBDT‐4T was copolymerized with di(thiophenyl)difluorobenzothiadiazole (FBT) and fluorothienothiophene (FTT) monomers to yield PTBDT‐FBT and PTBDT‐FTT, which showed high decomposition temperatures (421 and 408°C) and deep‐lying HOMO levels (−5.80 and −5.84 eV). The inverted solar cell device using PTBDT‐FBT:PC71BM (1:1 in wt%) blend showed a power conversion efficiency (PCE) of 4.16%, while the device using PTBDT‐FTT:PC71BM (1:2 in wt%) blend showed a PCE of 3.98%.