New Fused Bis-Thienobenzothienothiophene Copolymers and Their Use in Organic Solar Cells and Transistors

A new tetradodecyl-substituted DTBTBT donor unit is synthesized by a specific bis-annulation via Suzuki–Miyaura coupling and successfully incorporated into light absorbing electron donor copolymers for OPV and hole and electron transport OFET polymer devices. All copolymers (DTBTBT-co-benzothiadiazole (Bz), DTBTBT-co-thiophene (T) and DTBTBT-co-thienothiophene (TT)) show fully coplanar backbones and strong intermolecular interactions. The DTBTBT-Bz copolymer led to a deep HOMO level (−5.2 eV) and thus a large Voc value of 0.92 V with PC71BM as electron acceptor and a PCE of 3.7% with a Jsc of 6.78 mA/cm2 could be obtained. A hole mobility of 0.1 cm2/(V s) has been observed for the highly coplanar and more crystalline DTBTBT-T copolymer.