As new and better materials are implemented for organic electrochemical transistors (OECTs), it becomes increasingly important to adopt more economic and environmentally friendly synthesis pathways with respect to conventional transition-metal-catalyzed polymerizations. Herein, a series of novel n-type donoracceptor-conjugated polymers based on glycolated lactone and bis-isatin units are reported. All the polymers are synthesized via green and metal-free aldol polymerization. The strong electron-deficient lactone-building blocks provide low-lying lowest unoccupied molecular orbital (LUMO) and the rigid backbone needed for efficient electron mobility up to 0.07 cm 2 V −1 s −1 . Instead, polar atoms in the backbone and ethylene glycol side chains contribute to the ionic conductivity. The resulting OECTs exhibit a normalized maximum transconductance g m,norm of 0.8 S cm −1 and a μC* of 6.7 F cm −1 V −1 s −1 . Data on the microstructure show that such device performance originates from a unique porous morphology together with a highly disordered amorphous microstructure, leading to efficient ion-to-electron coupling. Overall, the design strategy provides an inexpensive and metal-free polymerization route for high-performing n-type OECTs.

Highly efficient mixed ionic and electronic conduction is critical to developing high‐performance organic electrochemical transistors (OECTs) devices. While currently, the n‐type small molecules mixed conductors design strategy remains extremely lacking. Herein, ethylene glycol (EG) chain substituted electron‐deficient naphthalene bis‐isatin and rhodanine acceptor units with easily accessible steps are rationally fused, affording fused and planar novel semiconductors with weak intramolecular S–O ‘conformation locks', where gNR with EG side chain and hgNR with hybrid alkyl‐EG side chain. The rigid, planar and highly electron‐deficient skeleton enables the resulting small molecule semiconductors to be efficient mixed ionic‐electronic conductors with very high OECT electron mobility up to 0.01 cm2 V−1 s−1. Remarkedly, gNR displays the record value of geometry‐normalized transconductance of 0.4 S cm−1 and μC* of 2.6 F V−1 cm−1 s−1, which can also be compared with the state‐of‐art n‐type semiconducting polymers in OECTs. Moreover, the effect of the alkyl spacer on the n‐type mixed ionic and electronic conduction features of the small molecule materials is investigated. The fused electron‐deficient acceptor‐acceptor (A–A) system with intramolecular conformation lock design strategy in this work provides a new avenue to realize next‐generation high‐performance small molecule mixed ionic and electronic conductors for OECT materials.

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.

Small-molecule semiconductors used as the channel of organic electrochemical transistors (OECTs) have been rarely reported despite their inherent advantages of well-defined molecular weight, convenient scale-up synthesis, and good performance reproducibility. Herein, three small molecules based on perylene diimides are readily prepared for n-type OECTs. The final molecules show preferred energy levels, tunable backbone conformation, and high film crystallinity, rendering them good n-type dopability, favorable volumetric capacities, and substantial electron mobilities. Consequently, the OECTs afford a record-low threshold voltage of 0.05 V and a normalized peak transconductance of 4.52 × 10–2 S cm–1, as well as impressive long-term cycling stability. Significantly, the OECTs utilized for hydrogen peroxide sensing are further demonstrated with a detection limit of 0.75 μM. This work opens the possibility of developing nonfullerene small molecules as superior n-type OECT materials and provides important insights for designing high-performance small-molecule mixed ion-electron conductors for OECTs and (bio)­sensors.

Tuning the film morphology and aggregated structure is a vital means to improve the performance of the mixed ionic–electronic conductors in organic electrochemical transistors (OECTs). Herein, three fluorinated alcohols (FAs), including 2,2,2-trifluoroethanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and perfluoro-tert-butanol (PFTB), were employed as the alternative solvents for engineering the n-type small-molecule active layer gNR. Remarkedly, an impressive μC* of 5.12 F V–1 cm–1 s–1 and a normalized transconductance of 1.216 S cm–1 are achieved from the HFIP-fabricated gNR OECTs, which is three times higher than that of chloroform. The operational stability has been significantly enhanced by the FA-fabricated devices. Such enhancements can be ascribed to the aggregation-induced structural ordering by FAs during spin coating, which optimizes the microstructure of the films for a better mixed ion and electron transport. These results prove the huge research potential of FAs to improve OECT materials’ processability, device performance, and stability, therefore promoting practical bio-applications.

The primary challenge for n‐type small‐molecule organic electrochemical transistors (OECTs) is to improve their electron mobilities and thus the key figure of merit μC*. Nevertheless, few reports in OECTs have specially proposed to address this issue. Herein, we report a 10‐ring‐fused polycyclic π‐system consisting of the core of naphthalene bis‐isatin dimer and the terminal moieties of rhodanine, which features intramolecular noncovalent interactions, high π‐delocalization and strong electron‐deficient characteristics. We find that this extended π‐conjugated system using the ring fusion strategy displays improved electron mobilities up to 0.043 cm2 V−1 s−1 compared to our previously reported small molecule gNR, and thereby leads to a remarkable μC* of 10.3 F cm−1 V−1 s−1 in n‐type OECTs, which is the highest value reported to date for small‐molecule OECTs. This work highlights the importance of π‐conjugation extension in polycyclic‐fused molecules for enhancing the performance of n‐type small‐molecule OECTs.

An n-type conjugated polymer based on diazaisoindigo (AIID) and fluorinated thiophene units is introduced. Combining the strong electron-accepting properties of AIID with backbone fluorination produced gAIID-2FT, leading to organic electrochemical transistors (OECTs) with normalized values of 4.09 F cm −1 V −1 s −1 and a normalized transconductance (g m,norm ) of 0.94 S cm −1 . The resulting OECTs exhibit exceptional operational stability and long shelf-life in ambient conditions, preserving 100% of the original maximum drain current after over 3 h of continuous operation and 28 days of storage in the air. Our work highlights the advantages of integrating strong electron acceptors with donor fluorination to boost the performance and stability of n-type OECTs.