Vinyl-Flanked Diketopyrrolopyrrole Polymer/MoS₂ Hybrid for Donor–Acceptor Semiconductor Photodetection

Polymers containing the 1,4-diketo-pyrrolo[3,4- c ]pyrrole (diketopyrrolopyrrole, DPP) unit are highly desirable for optoelectronic devices. However, the requirements for the substituents flanking the DPP unit at the 3,6-positions are limited to aryl groups due to the lack of synthetic methods to prepare other substituted DPP. This paper describes the synthesis, characterization, and application of the first vinyl-flanked DPP polymers: DPP-vinyl-thiophene-vinyl ( PDPPVTV ) and DPP-vinyl-thiophene-thiophene ( PDPPVTT ). The position of the vinyl group is varied to determine its effect on the physical and optoelectrical properties of the polymers. The semicrystalline polymers record moderate molecular weights ( M n ∼ 25–30 kDa), good solubility in chloroform, and high thermal stabilities ( T d onset ∼ 400 °C). Both polymers have broad absorption bands in the solid state (abs λ max ∼ 800 nm) that extend into the near-infrared (NIR) region (900–1000 nm). PDPPVTT has two orders of magnitude higher hole mobility than PDPPVTV (0.25 vs 0.0018 cm 2 V –1 s –1 ) and is used as a coating material in a MoS 2 FET device. The PDPPVTT /2D MoS 2 hybrid device shows higher photoresponsivity in the NIR region (10 3 A/W at 800 nm and 10 2 A/W at 1050 nm) than the pristine MoS 2 photodetector (10 2 A/W at 800 nm and 0 A/W at 1050 nm).