A High‐Performance n‐Type Thermoelectric Polymer from C−H/C−H Oxidative Direct Arylation Polycondensation

Abstract

n‐Type conjugated polymers (CPs) are crucial in the applications of organic electronics. Direct coupling of electron‐deficient C−H monomer via selective C−H activation, namely C−H/C−H oxidative direct arylation polycondensation (Oxi‐DArP), is an ideal approach toward such CPs. Herein, Oxi‐DArP is firstly adopted to synthesize a high‐performance n‐type CP using a newly developed monomer, i.e., 3,6‐di(thiazol‐5‐yl)‐diketopyrrolopyrrole (Tz‐5‐DPP). Tz‐5‐DPP based homopolymer PTz‐5‐DPP with a molecular weight of 22 kDa has been synthesized via Oxi‐DArP. After n‐doping, PTz‐5‐DPP films exhibited electric conductivity values up to 8 S cm−1 and power factors (PFs) up to 106 μW m−1 K−2. Notably, this PF value is the highest for n‐type polymer thermoelectric materials to date. The Oxi‐DArP synthesis and the excellent n‐type performance of the polymer make this work an important step toward the straightforward and sustainable preparation of high‐performance n‐type polymer semiconductors.

Synthesis and Characterization of Conjugated Polymers Based on Thieno[3,4‐b]Thiophene Quinoidal Unit

“…The LU-MOs were mainly located on the quinoidal moieties, while the HOMOs were mainly distributed on the aromatic comonomers (Figure 2c,d). This was also observed in the typical donoracceptor-type polymers, [55][56][57][58] and indicated that the electronwithdrawing ability of quinoidal unit is stronger than that of the aromatic comonomers.…”

Discovery of Organic Optoelectronic Materials Powered by Oxidative Ar–H/Ar–H Coupling

“…To tackle this concern, Deng and Geng proposed that Tz-5-DPP, wherein the C2−H of thiazole is free, could be an appealing alternative building block for highperformance n-type conjugated polymer construction. 132 Supported by DFT calculations, Tz-5-DPP, compared to Tz-2-DPP, exhibited comparable LUMO and HOMO energy levels, along with a flattened conformation attributed to intramolecular C−H•••O interactions that could facilitate the ntype mobility (Scheme 21A).…”

“…Thiazole-2-yl-substituted diketopyrrolopyrrole (Tz-2-DPP) has demonstrated its utility as a valuable building block in the creation of n-type conjugated polymers, owing to its low-lying frontier molecular orbital (FMO) energy levels. , Nonetheless, the remaining C5–H on the thiazole moiety of Tz-2-DPP is typically less reactive in the oxidative Ar–H/Ar–H coupling reaction. To tackle this concern, Deng and Geng proposed that Tz-5-DPP, wherein the C2–H of thiazole is free, could be an appealing alternative building block for high-performance n-type conjugated polymer construction . Supported by DFT calculations, Tz-5-DPP, compared to Tz-2-DPP, exhibited comparable LUMO and HOMO energy levels, along with a flattened conformation attributed to intramolecular C–H···O interactions that could facilitate the n-type mobility (Scheme A).…”

“…Dopant: N -DMBI = N , N -dimethyl-2-phenyl-2,3-dihydro-1 H -benzoimidazole. Adapted with permission from ref . Copyright 2022 John Wiley & Sons, Inc.…”

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

“…The availability of electron‐deficient building blocks is limited, thus severely restricting the further development of high‐performance n‐type polymer semiconductors. Some representative strong electron‐withdrawing building blocks have been reported in literatures, such as naphthalene diimide (NDI), [15] naphtho[2,3‐ b : 6,7‐ b ′]‐dithiophenediimide (NDTI), [16] bithiophene imide and derivatives (BTIn), [10a] benzodifurandione‐based oligo(p‐phenylene vinylene) (BDOPV), [17] B←N bridged bipyridine (BNBP), [13b] and diketopyrrolopyrrole (DPP) and derivatives [18] . These electron‐deficient building blocks have been widely investigated for constructing high‐performance n‐type polymer semiconductors.…”