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 × 10 ^-2 cm ² V ^-1 s ^-1 with an on-off ratio of 1.1 × 10 ⁷. The photovoltaic device based on the PaADTDPP:PC ₇₁BM (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.