Semiconducting Polymers Based on Simple Electron‐Deficient Cyanated trans‐1,3‐Butadienes for Organic Field‐Effect Transistors

Abstract

Developing high‐performance but low‐cost n‐type polymers remains a significant challenge in the commercialization of organic field‐effect transistors (OFETs). To achieve this objective, it is essential to design the key electron‐deficient units with simple structures and facile preparation processes, which can facilitate the production of low‐cost n‐type polymers. Herein, by sequentially introducing fluorine and cyano functionalities onto trans‐1,3‐butadiene, we developed a series of structurally simple but highly electron‐deficient building blocks, namely 1,4‐dicyano‐butadiene (CNDE), 3‐fluoro‐1,4‐dicyano‐butadiene (CNFDE), and 2,3‐difluoro‐1,4‐dicyano‐butadiene (CNDFDE), featuring a highly coplanar backbone and deep‐positioned lowest unoccupied molecular orbital (LUMO) energy levels (−3.03–4.33 eV), which render them highly attractive for developing n‐type semiconducting polymers. Notably, all these electron‐deficient units can be easily accessed by a two‐step high‐yield synthetic procedure from low‐cost raw materials, thus rendering them highly promising candidates for commercial applications. Upon polymerization with diketopyrrolopyrrole (DPP), three copolymers were developed that demonstrated unipolar n‐type transport characteristics in OFETs with the highest electron mobility of >1 cm2 V−1 s−1. Hence, CNDE, CNFDE, and CNDFDE represent a class of novel, simple, and efficient electron‐deficient units for constructing low‐cost n‐type polymers, thereby providing valuable insight for OFET applications.

Cyano‐Functionalized Pyrazine: A Structurally Simple and Easily Accessible Electron‐Deficient Building Block for n‐Type Organic Thermoelectric Polymers

“…1.85 cm 2 V À 1 s À 1 is much higher than recently reported polymer PCNDFDE-DPP. [24] Compared with other DPPbased copolymers, which typically show p-type or ambipolar transport behaviors, P(DPP-CNPz) and P(DPP-DCNPz) polymers only show unipolar n-type charge transport in OTFT. The result demonstrates that cyano-functionalized pyrazine (CNPz or DCNPz) is a strong electron-withdrawing building block for constructing unipolar n-type polymer semiconductors.…”

Synthesis and charge-transport properties of novel π-conjugated polymers incorporating core-extended naphtho[2,1-b:3,4-b′]dithiophene diimides

“…1 Modification of classic A units 8–16 [ e.g. , naphthalene diimide (NDI) and perylene diimide (PDI)] or the creation of novel A systems, 17–26 therefore, has recently become a popular subject of engineering the optoelectronic properties of CPSs.…”

“…Among the reported A units, 8,17–19,21,24 imide-functionalized aromatic hydrocarbons have attracted more attention in the synthetic elaboration of D–A type CPSs, due to the facts that: (1) the highly electron-poor imide unit allows a remarkable decrease in the frontier orbital energy levels of the resulting CPSs, which enables the achievement of desirable electron-transport performance; 7 (2) attaching long alkyl chains in the imide- N position offers a possibility of regulating the solution processability, solid-state organization, film crystallinity, and the optoelectronic properties of the target CPSs. 1 By introducing one or more imide groups into the aromatic ring systems, a series of imide-decorated A building blocks have been developed so far, 15,27–31 as typically exemplified by the well-known aromatic diimides such as PDI, 27 NDI, 28 and pyromellitic diimide 29 (PMDI) (see Fig.…”

Copolymers Based on π-Conjugated Asymmetric Naphthalene Diimide Building Blocks: Synthesis, Crystallography, and Structure–Property–Charge Transport/Photovoltaic Correlations

“…N-type (electron-transporting) conjugated polymers are essential components in diverse organic optoelectronic device technologies − such as all-polymer solar cells (APSCs), − thermoelectric generators, − n-type organic field-effect transistors (OFETs), , and others, , and for these reasons have been extensively studied over the past two decades. − N-type polymers based on the naphthalene diimide ( NDI ) acceptor unit are among the most investigated with poly­[ N , N ′-bis­(2-octyldodecyl)-naphthalene-1,4,5,8-bis­(dicarboximide)-2,6-diyl]- alt -5,5′-(2,2′-bithiophene) ( PNDITh2 or N2200 ) being the most prominent example, exhibiting an impressive electron mobility surpassing 6 cm 2 /(V s), low energetic disorder, and enabling APSC power conversion efficiencies >10%. − Since N2200 exhibits an important optoelectronic performance, several NDI -based donor–acceptor (D-A) copolymers with regioregular (RR) and regioirregular (RI) architectures have been developed. − However, NDI polymers achieved via/comprising an asymmetric NDI building block have not been reported to date due to limited synthetic protocols . Asymmetric structures generate local dipoles that can enhance interactions between neighboring molecules, hence favoring charge transport − as well as photovoltaic performance for several organic semiconductors. − Conventional Stille polycondensation reactions using dibrominated NDI building blocks and bis­(trialkylstannyl) aryl units as the starting materials have been the primary synthetic method for preparing NDI polymers; however, this approach is not particularly sustainable and using two symmetric building blocks only generates symmetric NDI polymers. , Kiriy and co-workers have developed an effective alternative polymerization protocol in which 2,6-di­(bromoaryl) substituted NDI units (Br-Het- NDI -Het-Br) are polymerized using activated zinc, which avoids the use of toxic stannanes.…”

“…N-type (electron-transporting) conjugated polymers are essential components in diverse organic optoelectronic device technologies 1−3 such as all-polymer solar cells (APSCs), 4−6 thermoelectric generators, 7−12 n-type organic field-effect transistors (OFETs), 13,14 and others, 15,16 and for these reasons have been extensively studied over the past two decades. 17−22 N-type polymers based on the naphthalene diimide (NDI) acceptor unit are among the most investigated with poly[N,N′bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene) (PNDITh2 or N2200) being the most prominent example, exhibiting an impressive electron mobility surpassing 6 cm 2 /(V s), low energetic disorder, and enabling APSC power conversion efficiencies >10%.…”