Conjugated random copolymer of benzodithiophene-difluorobenzene-diketopyrrolopyrrole-benzothiadiazole with a broad absorption range of 300–900 nm for bulk heterojunction solar cells

• A new D-A conjugated random copolymer as donor material in PSC.
• The copolymer exhibited a broad absorption from 300 nm to the near infrared region and a low optical bandgap of 1.51 eV.
• Preliminary studies of BHJ solar cells based on this polymer with PC60BM showed a PCE of 1.56% without any processing additives.
• This work has demonstrated that the polymerization of multiple different monomers (three electron acceptor units and one donor unit) can afford novel broad absorption conjugated polymers for solar cells.

A random donor–acceptor copolymer based on difluorobenzene (DFB), diketopyrrolo[3,4-c]pyrrole (DPP) and benzothiadiazole (BT) as co-electron acceptor units in conjugation with electron-donating benzodithiophene (BDT) unit has been synthesized and characterized. The copolymer exhibited a broad absorption from 300 nm to the near infrared region and a low optical bandgap of 1.51 eV. Preliminary studies of bulk heterojunction solar cells based on this polymer with PC60BM showed a power conversion efficiency (PCE) of 1.56% without any processing additives.