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Developing low‐cost and high‐performance n‐type polymer semiconductors is essential to accelerate the application of organic thermoelectrics (OTEs). To achieve this objective, it is critical to design strong electron‐deficient building blocks with simple structure and easy synthesis, which are essential for the development of n‐type polymer semiconductors. Herein, we synthesized two cyano‐functionalized highly electron‐deficient building blocks, namely 3,6‐dibromopyrazine‐2‐carbonitrile (CNPz) and 3,6‐Dibromopyrazine‐2,5‐dicarbonitrile (DCNPz), which feature simple structures and facile synthesis. CNPz and DCNPz can be obtained via only one‐step reaction and three‐step reactions from cheap raw materials, respectively. Based on CNPz and DCNPz, two acceptor–acceptor (A–A) polymers, P(DPP‐CNPz) and P(DPP‐DCNPz) are successfully developed, featuring deep‐positioned lowest unoccupied molecular orbital (LUMO) energy levels, which are beneficial to n‐type organic thin‐film transistors (OTFTs) and OTEs performance. An optimal unipolar electron mobility of 0.85 and 1.85 cm2 V−1 s−1 is obtained for P(DPP‐CNPz) and P(DPP‐DCNPz), respectively. When doped with N‐DMBI, P(DPP‐CNPz) and P(DPP‐DCNPz) show high n‐type electrical conductivities/power factors of 25.3 S cm−1/41.4 μW m−1 K−2, and 33.9 S cm−1/30.4 μW m−1 K−2, respectively. Hence, the cyano‐functionalized pyrazine CNPz and DCNPz represent a new class of structurally simple, low‐cost and readily accessible electron‐deficient building block for constructing n‐type polymer semiconductors. [ABSTRACT FROM AUTHOR]

Developing polymers with high electrical conductivity (σ) after n‐doping is a great challenge for the advance of the field of organic thermoelectrics (OTEs). Herein, we report a series of thiazole imide‐based n‐type polymers by gradually increasing selenophene content in polymeric backbone. Thanks to the strong intramolecular noncovalent N⋅⋅⋅S interaction and enhanced intermolecular Se⋅⋅⋅Se interaction, with the increase of selenophene content, the polymers show gradually lowered LUMOs, more planar backbone, and improved film crystallinity versus the selenophene‐free analogue. Consequently, polymer PDTzSI−Se with the highest selenophene content achieves a champion σ of 164.0 S cm−1 and a power factor of 49.0 μW m−1 K−2 in the series when applied in OTEs after n‐doping. The σ value is the highest one for n‐type donor‐acceptor OTE materials reported to date. Our work indicates that selenophene substitution is a powerful strategy for developing high‐performance n‐type OTE materials and selenophene incorporated thiazole imides offer an excellent platform in enabling n‐type polymers with high backbone coplanarity, deep‐lying LUMO and enhanced mobility/conductivity. [ABSTRACT FROM AUTHOR]

Polymerized small molecule acceptors have recently greatly facilitated the development of all‐polymer solar cells (All‐PSCs) with respect to the power conversion efficiencies (PCEs). However, high‐performance and low‐cost polymer donors for All‐PSCs are still lacking, limiting further large‐scale manufacturing of All‐PSCs. Herein, this work designs and synthesizes a new thiophene derivative, FETVT, featuring vinyl‐bridged fluorine and ester‐substituted monothiophene. Incorporation of FETVT into a polymer yields a high‐performance polythiophene derivative PFETVT‐T, which exhibits deep‐lying HOMO level, suitable solution pre‐aggregation ability, finely‐tuned polymer crystallinity, and appropriate thermodynamic miscibility with the polymer acceptor L15. As a result, binary based on PFETVT‐T achieves a record PCE of 11.81% with agood stability, representing a breakthrough for polythiophenes and their derivatives‐based All‐PSCs, which is also significantly higher than that (1.92%) of All‐PSCs based on its isomerized analog. Remarkably, PFETVT‐T achieves an impressive PCE exceeding 16% via the implementation of a ternary blend design. These findings offer a hopeful pathway toward attaining high‐performance, stable, and cost‐effective PSCs. [ABSTRACT FROM AUTHOR]

Designing n‐type polymers with high electrical conductivity remains a major challenge for organic thermoelectrics (OTEs). Herein, by devising a novel selenophene‐based electron‐deficient building block, the pronounced advantages of selenium substitution in simultaneously enabling advanced n‐type polymers is demonstrated with high mobility (≈2 orders of magnitude higher versus their sulfur‐based analogues due to both intensified intra‐ and inter‐chain interactions) and much improved n‐doping efficiency (enabled by the largely lowered LUMO level with a ≈0.2 eV margin) of the resulting polymers. Via side chain optimization and donor engineering, the selenium‐substituted polymer, f‐BSeI2TEG‐FT, achieves a highest conductivity of 103.5 S cm−1 and power factor of 70.1 µW m−1 K−2, which are among the highest values reported in literature for n‐type polymers, and f‐BSeI2TEG‐FT greatly outperformed the sulfur‐based analogue polymer by 40% conductivity increase. These results demonstrate that selenium substitution is a very effective strategy for improving n‐type performance and provide important structure‐property correlations for developing high‐performing n‐type OTE materials. [ABSTRACT FROM AUTHOR]

n‐Type semiconducting polymers with high thermoelectric performance remain challenging due to the scarcity of molecular design strategy, limiting their applications in organic thermoelectric (OTE) devices. Herein, we provide a new approach to enhance the OTE performance of n‐doped polymers by introducing acceptor‐acceptor (A‐A) type backbone bearing branched ethylene glycol (EG) side chains. When doped with 4‐(2,3‐dihydro‐1,3‐dimethyl‐1H‐benzimidazol‐2‐yl)‐N,N‐dimethylbenzenamine (N‐DMBI), the A‐A homopolymer PDTzTI‐TEG exhibits n‐type electrical conductivity (σ) up to 34 S cm−1 and power factor value of 15.7 μW m−1 K−2. The OTE performance of PDTzTI‐TEG is far greater than that of homopolymer PBTI‐TEG (σ=0.27 S cm−1), indicating that introducing electron‐deficient thiazole units in the backbone further improves the n‐doping efficiency. These results demonstrate that developing A‐A type polymers with EG side chains is an effective strategy to enhance n‐type OTE performance. [ABSTRACT FROM AUTHOR]

The development of high‐performance n‐type polymer semiconductors is powered by the design and synthesis of electron‐deficient building blocks with optimized physicochemical properties. By meticulously installing an imide group onto fluorene and its cyanated derivative, we report here two very electron‐deficient building blocks, imide‐functionalized fluorenone (FOI) and its cyanated derivative (FCNI), both featuring a deep‐lying lowest unoccupied molecular orbital energy level down to −4.05 eV and highly coplanar framework, endowing them ideal units for constructing n‐type polymers. Thus, a series of polymers are built from them, exhibiting unipolar n‐type transport character with a highest electron mobility of 0.11 cm2 V−1 s−1. Hence, FOI and FCNI offer a remarkable platform for accessing high‐performance n‐type polymers and the imide functionalization of appropriate (hetero)arenes is a powerful strategy for developing polymers with deep‐lying LUMOs for n‐type organic electronics. [ABSTRACT FROM AUTHOR]

• A thiol-ene click reaction was used to functionalize CNTs by thiol-ended hyperbranched polymers. • Thiol-functionalized CNTs showed well dispersion in epoxy resins. • Functionalized CNTs could increase conductivity and mechanical strength of epoxy resins. • The flexible and ellipsoidal hyperbranched polymers could deform and transfer the load. • A reinforcing mechanism was supposed and substantiated by SEM, TEM, XPS and Raman techniques. Carbon nanotubes (CNTs) have been considered as the attractively multifunctional nanomaterials for high conductivity and high strength, but it is still a challenge to prepare CNTs with high dispersion and their nanocomposites with simultaneous high strength and longation. Here, we used thiol-ended hyperbranched polymers to functionalize CNTs and obtain thiol-functionalized CNTs with excellent dispersion and good compatibility with epoxy resins matrix. The grafted thiol-ended hyperbranched polymers can supply a bridging function between epoxy resins and the CNTs to promote their interaction. The thermal conductivity, elongation, tensile, flexural and impact strengthes of thiol-functionalized CNTs/epoxy nanocomposites could be improved simultaneously by 23.33%, 37.46%, 60.74%, 26.72% and 86.71%, respectively. A reinforcing mechanism was supposed and substantiated by combining SEM, TEM, XPS and Raman techniques. The flexible and ellipsoidal hyperbranched polymers chains grafted on CNTs deform and transfer the load to increase mechanical strength and elongation. An efficient and environmentally-friendly route is introduced to functionalize CNTs and fabricate simultaneous high strength and high elongation CNTs/epoxy nanocomposites. [ABSTRACT FROM AUTHOR]

While the development of high-performing n-type polymer semiconductors remains a challenge, the involving of costly transition-metal catalysts and even toxic reagents during the preparation of these materials might also cause serious environmental issues. Herein, by devising two new aldehyde-functionalized bithiophene imide (BTI)-type building blocks, we designed and synthesized two acceptor-acceptor type n-type polymers, BTI-BD and BTI2-BD, on the basis of an environmentally benign, transition metal-free and thus cost-effective aldol condensation. The resulting polymers exhibited planar and rigid backbone conformations and low-lying LUMO energy levels close to −4.0 eV, thus leading to unipolar n-type tranport character with a highest electron mobility of 1.35 × 10−3 cm2 V−1 s−1 in organic field-effect transistors for the BTI2-BD polymer which features a higher molecular ordering in solid state. Our results demonstrate that the aldol polycondensation strategy could serve as a cheaper and more ecofriendly alternative to the convential transition metal-catalyzed cross-coupling reactions for constructing n-type acceptor-acceptor polymers with unipolar n-type charge transport characteristics. By devising two aldehyde-functionalized bithiophene imide monomers, two n-type acceptor-acceptor polymers were developed based on a costly and eco-friendly aldol polycondensation procedure and delivered encouraging unipolar electron charge transport properties. [Display omitted] • Two aldehyde-functionalized bithiophene imide-based building blocks, namely BTI1-CHO and BTI2-CHO, were devised. • Two acceptor-acceptor polymers were prepared via metal-free, atom-economic aldol condensation. • Unipolar electron mobilities of up to 1.35 × 10−3 cm2/V·s was achieved in OFETs. [ABSTRACT FROM AUTHOR]