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Donor–acceptor (D‐A) conjugated polymers have demonstrated great potential in organic field‐effect transistors application, and their aggregated structure is a crucial factor for high charge mobility. However, the aggregated structure of D‐A conjugated polymer films is complex and the structure–property relationship is difficult to understand. This review provides an overview of recent progress in controlling the aggregated structure of D‐A conjugated polymer films for higher mobility, including the mechanisms, methods, and properties. We first discuss the multilevel microstructures of D‐A conjugated polymer films, and then summarize the current understanding of the relationship between film microstructures and charge transport properties. Subsequently, we review the theory of D‐A conjugated polymer crystallization. After that, we summarize the common methods to control the aggregated structure of semi‐crystalline and near‐amorphous D‐A conjugated polymer films, such as crystallites and aggregates, tie chains, film alignment, and attempt to understand them from the basic theory of polymer crystallization. Finally, we provide the current challenges in controlling the aggregated structure of D‐A conjugated polymer films and in understanding the structure–property relationship. Donor‐acceptor (D‐A) conjugated polymers have demonstrated great potential in organic field‐effect transistors (OFETs) application, and their aggregated structure is a crucial factor for high charge mobility. This review provides an overview of recent progress in controlling the aggregated structure of semi‐crystalline and near‐amorphous D‐A conjugated polymers, including crystallization theories, control methods, aggregated structures, and charge mobilities.

Although polycyclic conjugated hydrocarbons (PCHs) and their analogues have gained great progress in the fields of organic photoelectronic materials, the in‐depth study on present PCHs is still limited to hexacene or below because longer PCHs are insoluble, unstable, and tediously synthesized. Very recently, various strategies including on‐surface synthesis are developed to address these issues and many higher novel PCHs are constructed. Therefore, it is necessary to review these advances. Here, the recent synthetic approach, basic physicochemical properties, single‐crystal packing behaviors, and potential applications of the linearly fused PCHs (higher than hexacene), including acenes or π‐extended acenes with fused six‐membered benzenoid rings and other four‐membered, five‐membered or even seven‐membered and eight‐membered fused compounds, are summarized. Polycyclic conjugated hydrocarbons (PCHs) and their analogues have a wide range of applications in the fields of organic photoelectronic materials. This work provides a timely summary of recent advances in the latest synthetic routes to higher PCHs as well as their basic physicochemical properties, single crystal packing behaviors and potential applications.

Organic field‐effect transistors (OFETs) show great application potential in organic electronic and optoelectronic fields due to their excellent mechanical flexibility, low cost, and solution processing. However, grain boundaries (GBs) disrupt the aggregation state of organic semiconductor (OSC) films and hinder electrical performance and stability, which limits the application of OFETs. Besides, the sensitive nature of GBs is widely used in sensing, but detailed descriptions of the GBs are scarce. This review aims to fill this knowledge gap. The role of GBs and their effect on the performance and stability of OFETs are analyzed, followed by a detailed summary of the characterization of GBs. Then, strategies for suppressing the negative effects of GBs and utilizing the sensitive nature of GBs for application are proposed. Finally, potential research directions for GBs in OFETs are discussed.

The study of organic semiconductor single crystal (OSSC) arrays has recently attracted considerable interest given their potential applications in flexible displays, smart wearable devices, biochemical sensors, etc. Patterning of OSSCs is the prerequisite for the realization of organic integrated circuits. Patterned OSSCs can not only decrease the crosstalk between adjacent organic field‐effect transistors (OFETs), but also can be conveniently integrated with other device elements which facilitate circuits application. Tremendous efforts have been devoted in the controllable preparation of OSSC arrays, and great progress has been achieved. In this review, the general strategies for patterning OSSCs are summarized, along with the discussion of the advantages and limitations of different patterning methods. Given the identical thickness of monolayer molecular crystals (MMCs) which is beneficial to achieve super uniformity of OSSC arrays and devices, patterning of MMCs is also emphasized. Then, OFET performance is summarized with comparison of the mobility and coefficient of variation based on the OSSC arrays prepared by different methods. Furthermore, advances of OSSC array‐based circuits and flexible devices of different functions are highlighted. Finally, the challenges that need to be tackled in the future are presented. In this review, the general strategies for patterning organic semiconductor single crystals (OSSCs) are summarized, especially, patterning of monolayer molecular crystals (MMCs) is emphasized. Then, organic field‐effect transistor (OFET) performance is generalized based on the OSSC arrays. Furthermore, advances of OSSC array‐based applications are highlighted. Finally, the challenges that need to be tackled in the future are presented.

Flexible pressure sensors based on organic field‐effect transistors (OFETs) have emerged as promising candidates for electronic‐skin applications. However, it remains a challenge to achieve low operating voltages of hysteresis‐free flexible pressure sensors. Interface engineering of polymer dielectrics is a feasible strategy toward sensitive pressure sensors based on low‐voltage OFETs. Here, a novel type of solution‐processed bilayer dielectrics is developed by combining a thick polyelectrolyte layer of polyacrylic acid (PAA) with a thin poly(methyl methacrylate) (PMMA) layer. This bilayer dielectric can provide a vertical phase separation structure from hydrophilic interface to hydrophobic interface which adjoins well to organic semiconductors, leading to improved stability and remarkably reduced leakage currents. Consequently, OFETs using the PMMA/PAA dielectrics reveal greatly suppressed hysteresis and improved mobility compared to those with a pure PAA dielectric. Using the optimized PMMA/PAA dielectric, flexible OFET‐based pressure sensors that show a record high sensitivity of 56.15 kPa−1 at a low operating voltage of −5 V, a fast response time of less than 20 ms, and good flexibility are further demonstrated. The salient features of high capacitance, good dielectric performance, and excellent reliability of the bilayer dielectrics promise a bright future of flexible sensors based on low‐voltage OFETs for wearable electronic applications. Flexible low‐voltage organic field‐effect transistors (OFETs) for pressure‐sensing applications are demonstrated by using solution‐processed poly(methyl methacrylate)/polyacrylic acid dielectrics that achieve greatly enhanced charge transportation with reduced hysteresis. The resulting OFET‐based pressure sensors exhibit a record high sensitivity of 56.15 kPa−1 at a low operating voltage of −5 V, a fast response time of <20 ms, and good flexibility.

A key component of organic bioelectronics is electrolyte‐gated organic field‐effect transistors (EG‐OFETs), which have recently been used as sensors to demonstrate label‐free, single‐molecule detection. However, these devices exhibit limited stability when operated in direct contact with aqueous electrolytes. Ultrahigh stability is demonstrated to be achievable through the utilization of a systematic multifactorial approach in this study. EG‐OFETs with operational stability and lifetime several orders of magnitude higher than the state of the art have been fabricated by carefully controlling a set of intricate stability‐limiting factors, including contamination and corrosion. The indacenodithiophene‐co‐benzothiadiazole (IDTBT) EG‐OFETs exhibit operational stability that exceeds 900 min in a variety of widely used electrolytes, with an overall lifetime exceeding 2 months in ultrapure water and 1 month in various electrolytes. The devices were not affected by electrical stress‐induced trap states and can remain stable even in voltage ranges where electrochemical doping occurs. To validate the applicability of our stabilized device for biosensing applications, the reliable detection of the protein lysozyme in ultrapure water and in a physiological sodium phosphate buffer solution for 1500 min was demonstrated. The results show that polymer‐based EG‐OFETs are a viable architecture not only for short‐term but also for long‐term biosensing applications. Electrolyte‐gated organic field‐effect transistors (EG‐OFETs) have exhibit limited stability when operated in direct contact with aqueous electrolytes. We demonstrate that ultrahigh stability can be achieved by carefully controlling a set of intricate stability‐limiting factors, including contamination and corrosion. We fabricated indacenodithiophene‐co‐benzothiadiazole (IDTBT) EG‐OFETs whose operational stability exceeds 900 min in a variety of widely used electrolytes. Moreover, their overall lifetime exceeds 2 months in ultrapure water and 1 month in various electrolytes.

n‐Type organic electrochemical transistors (OECTs) and organic field‐effect transistors (OFETs) are less developed than their p‐type counterparts. Herein, polynaphthalenediimide (PNDI)‐based copolymers bearing novel fluorinated selenophene‐vinylene‐selenophene (FSVS) units as efficient materials for both n‐type OECTs and n‐type OFETs are reported. The PNDI polymers with oligo(ethylene glycol) (EG7) side chains P(NDIEG7‐FSVS), affords a high µC* of > 0.2 F cm−1 V−1 s−1, outperforming the benchmark n‐type Pg4NDI‐T2 and Pg4NDI‐gT2 by two orders of magnitude. The deep‐lying LUMO of −4.63 eV endows P(NDIEG7‐FSVS) with an ultra‐low threshold voltage of 0.16 V. Moreover, the conjugated polymer with octyldodecyl (OD) side chains P(NDIOD‐FSVS) exhibits a surprisingly low energetic disorder with an Urbach energy of 36 meV and an ultra‐low activation energy of 39 meV, resulting in high electron mobility of up to 0.32 cm2 V−1 s−1 in n‐type OFETs. These results demonstrate the great potential for simultaneously achieving a lower LUMO and a tighter intermolecular packing for the next‐generation efficient n‐type organic electronics. Novel PNDI‐based polymers bearing fluorinated selenophene‐vinylene‐selenophene (FSVS) are synthesized. The glycolated P(NDIEG7‐FSVS) with a deep‐lying LUMO of −4.63 eV gives an ultra‐low threshold voltage of 0.16 V, yielding a µC* > 0.2 F cm−1 V−1 s−1 in n‐type OECTs; the alkylated P(NDIOD‐FSVS), with a low Urbach energy of 36 meV and a low activation energy of 39 meV, exhibits electron mobility of > 0.3 cm2 V−1 s−1 in n‐type OFETs.

Over the past three decades, the mobility of organic field‐effect transistors (OFETs) has been improved from 10−5 up to over 10 cm2 V−1 s−1, which reaches or has already satisfied the requirements of demanding applications. However, pronounced nonideal behaviors in current–voltage characteristics are commonly observed, which indicates that the reported mobilities may not truly reflect the device properties. Herein, a comprehensive understanding of the origins of several observed nonidealities (downward, upward, double‐slope, superlinear, and humped transfer characteristics) is summarized, and how to extract comparatively reliable mobilities from nonideal behaviors in OFETs is discussed. Combining an overview of the ideal and state‐of‐the‐art OFETs, considerable possible approaches are also provided for future OFETs. Nonideal current–voltage characteristics make the mobility that truly reflects the device performance hard to be extracted. A fundamental understanding is necessary to overcome this issue. Herein, the observed nonideal behaviors of organic field‐effect transistors are summarized and analyzed, and solutions for future device engineering toward ideal organic field‐effect transistors are provided.

Electrohydrodynamic (EHD) printing technique, which deposits micro/nanostructures through high electric force, has recently attracted significant research interest owing to their fascinating characteristics in high resolution (<1 μm), wide material applicability (ink viscosity 1–10 000 cps), tunable printing modes (electrospray, electrospinning, and EHD jet printing), and compatibility with flexible/wearable applications. Since the laboratory level of the EHD printed electronics' resolution and efficiency is gradually approaching the commercial application level, an urgent need for developing EHD technique from laboratory into industrialization have been put forward. Herein, we first discuss the EHD printing technique, including the ink design, droplet formation, and key technologies for promoting printing efficiency/accuracy. Then we summarize the recent progress of EHD printing in fabrication of displays, organic field‐effect transistors (OFETs), transparent electrodes, and sensors and actuators. Finally, a brief summary and the outlook for future research effort are presented. Electrohydrodynamic (EHD) printing presents unique advantages of ultra‐high resolution (<1 μm), wide ink compatibility (e.g., perovskite, quantum dots, 2D materials), and powerful multi‐mode‐tunability. To promote its practical applications in new materials patterning and industrial manufacturing, this review highlights the EHD based ink design, droplet formation, key technologies for promoting efficiency/accuracy, and wide applications in electronics fabrication.

Indigo is one of the most well‐known natural dyes and has attracted significant research interest due to its low cost and exceptional stability. Notably, bay‐annulated indigo (BAI) has been reported as an effective electron acceptor and is widely used in various applications. Herein, a methylthio‐substituted BAI derivative, compound 1, is successfully synthesized and the impact of methylthio substitution on its optoelectronic properties is investigated. UV–vis absorption and fluorescence spectra reveal that compound 1 displays a significant redshift compared to the nonmethylthio‐substituted compound 2. Cyclic voltammetry measurements and density functional theory calculations indicate that compound 1 has a narrower highest occupied molecular orbital and lowest unoccupied molecular orbital gap, demonstrating the prominent influence of methylthio side chains in modulating molecular electronic properties. Importantly, the organic field‐effect transistor device based on compound 1 exhibits a hole mobility 3.5 times higher than that of the nonmethylthio‐substituted compound 2. Furthermore, atomic force microscopy characterization reveals the formation of needle‐like crystallites in the compound 1 film after annealing, whereas compound 2 forms an amorphous thin film. These results suggest that methylthiolation is an effective strategy for tuning intermolecular interactions in novel BAI derivatives, and compound 1 is a promising hole‐transporting material. A methylthio‐substituted bay‐annulated indigo (BAI) derivative (compound 1) with enhanced optoelectronic properties is synthesized. Compared to nonmethylthio‐substituted compound 2, compound 1 exhibits a redshifted absorption and 3.5‐fold higher hole mobility in organic field‐effect transistors. These results demonstrate that methylthiolation effectively tunes intermolecular interactions and electronic properties, making compound 1 a promising hole‐transporting material for organic electronics.