Abstract
Herein we present an extension of our work on indacenodithiophenes (IDT) by replacing the central benzene ring with a thieno(3,2-b) thiophene unit. This newly developed thieno[3,2-b] thieno bisthiophene (4T) donor moiety was synthesized from commercially available reagents and incorporated into a series of donor-acceptor polymers. We will discuss the pronounced donating character of 4T compared to IDT and the choice of bridging atom in those new polymers with an emphasis on field effect transistor and photovoltaic device performance.