New copolymers with fluorinated and non-fluorinated benzothiadiazole units for efficient single layer near infra-red photodiodes with fast time response

Abstract We describe the synthesis and photodetecting properties of new, low band-gap copolymers: P1 with 5,6-difluoro-2,1,3-benzothiadiazole and P2 with 2,1,3-benzothiadiazole, both containing diketopyrrolopyrrole acceptor units. These compounds have been used for fabrication of single layer, solution processed photodetectors. For this purpose, two blends with fullerene derivative (6,6)-phenyl-C61-butyric acid methyl ester ([60]PCBM): P1:[60]PCBM and P2:[60]PCBM, were prepared and applied as active layers in bulk-heterojunction photodiodes. For near infrared light (810 nm), these photodetectors, in spite of single layer structure, display competitive performance, showing specific detectivity up to 5·10 11 Jones, responsivity up to 0.3 A/W and rise and fall times of the transient signals below 10 μs.