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

Polymerscontaining the 1,4-diketo-pyrrolo[3,4-c]pyrrole (diketopyrrolopyrrole,DPP) unit are highly desirableforoptoelectronic devices. However, the requirements for the substituentsflanking the DPP unit at the 3,6-positions are limited to aryl groupsdue to the lack of synthetic methods to prepare other substitutedDPP. This paper describes the synthesis, characterization, and applicationof 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 effecton the physical and optoelectrical properties of the polymers. Thesemicrystalline polymers record moderate molecular weights (M (n) similar to 25-30 kDa), good solubilityin chloroform, and high thermal stabilities (T (d) onset similar to 400 degrees C). Both polymers have broad absorptionbands in the solid state (abs lambda(max) similar to 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 materialin a MoS2 FET device. The PDPPVTT/2D MoS2 hybrid device shows higher photoresponsivity in the NIR region(10(3) A/W at 800 nm and 10(2) A/W at 1050nm) than the pristine MoS2 photodetector (10(2) A/W at 800 nm and 0 A/W at 1050 nm).