New Angular-Shaped and Isomerically Pure Anthradithiophene with Lateral Aliphatic Side Chains for Conjugated Polymers: Synthesis, Characterization, and Implications for Solution-Prossessed Organic Field-Effect Transistors and Photovoltaics

An isomerically pure anti-anthradithiophene (aADT) arranged in an angular shape is developed. Formation of the framework of aADT incorporating four lateral alkyl substituents was accomplished by a one-pot benzannulation via multiple Suzuki coupling. This newly designed 2,8-stannylated aADT monomer was copolymerized with a ditheniodiketopyrrolopyrrole (DPP) unit and a bithiophene unit, respectively, to furnish an alternating donor-acceptor copolymer poly(anthradithiophene-alt-dithienyldiketopyrrolopyrrole) (PaADTDPP) and a thiophene-rich poly(anthradithiophene-alt-bithiophene) (PaADTT). PaADTT with crystalline nature achieved a high FET mobility of 7.9 x 10(-2) cm(-2) V-1 s(-1) with an on-off ratio of 1.1 x 10(7). The photovoltaic device based on the PaADTDPP:PC71BM (1:2.5, w/w) blend exhibited a V-oc, of 0.66 V, a J(sc) of 9.49 mA/cm(2), and a FF of 58.4%, delivering a power conversion efficiency (PCE) of 3.66%. By adding 1.5 vol % 1-chloronaphthalene (CN) as a processing additive, the PCE can be improved to 4.24%. We demonstrated that these angular-shaped and alkylated aADT-based polymers have better organic photovoltaic (OPVs) and field-effect transistor (FETs) characteristics than the linear-shaped ADT-containing polymers.