Donor–acceptor copolymers featuring electron-deficient isoindigo units and electron-rich 3,4-ethylenedioxy (EDOT) groups are presented as new materials for accumulation mode organic electrochemical transistors (OECTs). Grafting hybrid alkyl–ethylene glycol side chains on the isoindigo units of the copolymer leads to OECTs with outstanding substrate adhesion and operational stability in contact with an aqueous electrolyte, as demonstrated by their preserved performance after extensive ultrasonication (1.5 h) or after continuous on–off switching for over 6 h. Hybrid side chains outperform copolymers with alkyl only or ethylene glycol only side chains, which retain only 27% and 10% of the on currents after 40 min of on–off switching, respectively, under the same biasing conditions. These devices are promising candidates for in vitro and in vivo bioelectronics, applications where stability as well as robust adhesion of the conjugated polymer to the substrate are essential.

Two D–A type polymers based on the gTDPP as the acceptor and gTVT and gTBTT as the donor have been developed. The donor unit affects the backbone curvature and the aggregation properties of the mixed conductors, regulating their performance in OECTs.

Porous morphologies have shown great potential in optimizing the capacitance and charge carrier transport for semiconducting polymers in organic electrochemical transistors (OECTs). Nevertheless, it remains arduous and time-consuming to obtain such desired microstructures due to the requirement of rigorous humidity control and templates/additives. Herein, three new glycolated conjugated polymers based on a fused-ring cyclopentadithiophene (CPDT) skeleton are developed, which feature readily obtained large-area porous thin films via spin-casting from binary solvent mixtures under ambient conditions. These polymers afford fascinating capacitances reaching a maximum of 353 F cm −3 , which is the highest value reported to date for p-type OECT materials. The optimal combination of volumetric capacitance and hole mobility in a representative polymer enables the fabrication of OECTs with a high μC* value up to 476 F cm −1 V −1 s −1 and a current retention of 98% upon 600 switching cycles. Moreover, the corresponding flexible OECTs exhibit exceptional mechanical stability at various bending radii down to 5 mm and under repetitive bending cycles. This work provides a simple yet effective binary solvent strategy to fabricate porous conjugated polymers for high-performance OECTs and flexible devices, which will further advance the development of organic mixed ionic−electronic conductors in OECT research fields and beyond.

Conspectus Because of their low-temperature processing properties and inherent mechanical flexibility, semiconducting materials are promising candidates for enabling flexible displays, renewable energy, biological sensors, and healthcare. Progress has been made in materials performance by developing judicious materials design strategies. For example, improvements in electron transport have required new electron-deficient aromatics. Among them, isoindigo (IID) is an important functional group utilized in conjugated aromatics, where the structure combines two sets of five-membered electron-withdrawing lactam rings, exhibiting enhanced solubility, excellent chemical and thermal stabilities, broad absorption, and intriguing electron affinity. In the past decade, researchers have mainly focused on IID-based materials. However, the effect of heteroatom modification of the IID core has rarely been systemically investigated. In conventional conjugated polymers, single bonds connect the monomers, leading to energetic disorder and torsion defects, while ladder-type polymers are often intractable because of their fused nature. In this regard, the molecular design of new π scaffolds based on IID is central to the development of high-performance semiconductor polymers. Especially, a complete refresh of molecular design strategies and novel conjugated polymers with unique structures are needed to circumvent the disadvantages of the conventional ladder-type polymers. In this Account, we systematically summarize our recent progress in the design, synthesis, and structure–property relationships of IID- and particularly hetero-IID-based functional materials. More specifically, starting with molecular engineering of hetero-IIDs with variable electronic effects, conjugation lengths, and numbers of heterorings, we discuss the effect of the heteroring on the absorption spectra and energy levels. Additionally, we investigate a series of electron-withdrawing substitution of IIDs and hetero-IIDs and their molecular self-assembly behavior and the device performance. Furthermore, we discuss a series of IID–bis­(EDOT) copolymers with hydrophilic ethylene glycol side chains for accumulation-mode organic thin-film electrochemical transistors, in which the relationships among the molecular structure, operational stability, film morphology, and device performance were revealed. Compared with IID polymers, the HOMO levels and optical band gaps of the thiophene and thienothiophene IID copolymers markedly decrease, and these polymers exhibit ambipolar charge transport. When we further expanded the IID core to a thieno­[3,2-b]­[1]­benzothiophene isoindigo (TBTI) core, such as in TBTIT, bulk-heterojunction solar cells employing this polymer class as the electron donor achieved good efficiency for additive- and annealing-free device conditions. When we introduced electron-deficient pyridine on the IID core, both the LUMO and HOMO energy levels of the copolymers markedly decreased, which significantly improved the electron mobility. In addition, we co...

Propylene and butylene glycol oligoether chains have been employed as alternatives to ethylene glycol in thiophene based semiconductors for OECTs. Their impact on electrochemical, microstructure, and swelling properties are discussed.