Considering there is growing interest in the superior charge transport in the ( E )-2-(2-(thiophen-2-yl)-vinyl)thiophene (TVT)-based polymer family, an essential step forward is to provide a deep and comprehensive understanding of the structure-property relationships with their polymer analogs. Herein, a carefully chosen set of DPP-TVT-n polymers are reported here, involving TVT and diketopyrrolopyrrole (DPP) units that are constructed in combination with varying thiophene content in the repeat units, where n is the number of thiophene spacer units. Their OFET characteristics demonstrate ambipolar behavior; in particular, with DPP-TVT-0 a nearly balanced hole and electron transport are observed. Interestingly, the majority of the charge-transport properties changed from ambipolar to p -type dominant, together with the enhanced hole mobilities, as the electron-donating thiophene spacers are introduced. Although both the lamellar d -spacings and π-stacking distances of DPP-TVT-n decreased with as the number of thiophene spacers increased, DPP-TVT-1 clearly shows the highest hole mobility (up to 2.96 cm 2 V −1 s −1 ) owing to the unique structural conformations derived from its smaller paracrystalline distortion parameter and narrower plane distribution relative to the others. These in-depth studies should uncover the underlying structure-property relationships in a relevant class of TVT-like semiconductors, shedding light on the future design of top-performing semiconducting polymers.
Over the past few years, one of the most remarkable advances in the field of polymer solar cells (PSCs) has been the development of fluorinated 2,1,3-benzothiadiazole (BT)-based polymers that lack the solid working principles of previous designs, but boost the power conversion efficiency. To assess a rich data set for the influence of the fluorinated BT units on the charge-transport characteristics in organic field-effect transistors (OFETs), we synthesized two new polymers (PDPP-FBT and PDPP-2FBT) incorporating diketopyrrolopyrrole (DPP) and either single- or double-fluorinated BT and thoroughly investigated them via a range of techniques. Unlike the small differences in the absorption properties of PDPP-FBT and its nonfluorinated analogue (PDPP-BT), the introduction of doubly fluorinated BT into the polymer backbone induces a noticeable change in its optical profiles and energy levels, which results in a slightly wider bandgap and deeper HOMO for PDPP-2FBT, relative to the others. Grazing incidence X-ray diffraction (GIXD) analysis reveals that both fluorinated polymer films have long-range orders along the out-of-plane direction, and π-π stacking in the in-plane direction, implying semicrystalline lamellar structures with edge-on orientations in the solid state. Thanks to the strong intermolecular interactions and highly electron-deficient π-systems driven by the inclusion of F atoms, the polymers exhibit electron mobilities of up to 0.42 and 0.30 cm2 V(-1) s(-1) for PDPP-FBT and PDPP-2FBT, respectively, while maintaining hole mobilities higher than 0.1 cm2 V(-1) s(-1). Our results highlight that the use of fluorinated BT blocks in the polymers is a promising molecular design strategy for improving electron transporting performance without sacrificing their original hole mobility values.
Poly(3,4-ethyldioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), as an thermoelectric(TE) material, exhibits a high electrical conductivity and ZT value (10 À1 -10 0 ). Nevertheless, a low thermovoltage of the organic thermoelectric materials must be overcome, in comparison to that of semi metals. Recently, to address these challenges, several researchers have investigated PEDOT:PSS/carbon material composites.Herein, a transparent and flexible hybrid film made up of rapid thermal chemical vapor deposition (RTCVD) graphene and PEDOT:PSS results in enhanced TE performance. The PEDOT:PSS was synthesized by oxidative polymerization, and the hybrid process of the graphene film and PEDOT:PSS film was conducted using the layer-by-layer method. The results of AFM and Raman spectroscopy revealed that the synergistic effect through composite films improved the electrical properties. The maximum electrical conductivity and power factor of the RTCVD graphene/PEDOT:PSS (RCG/P) hybrid film were 1096 S cm À1 and 57.9 mW m À1 K
À2, respectively. In addition, the RCG/P hybrid film exhibited excellent mechanical flexibility and stability.
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