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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. [ABSTRACT FROM AUTHOR]

Polymer nanowire (NW) organic field-effect transistors (OFETs) integrated on highly aligned large-area flexible substrates are candidate structures for the development of high-performance flexible electronics. This work presents a universal technique, coaxial focused electrohydrodynamic jet (CFEJ) printing technology, to fabricate highly aligned 90-nm-diameter polymer arrays. This method allows for the preparation of uniformly shaped and precisely positioned nanowires directly on flexible substrates without transfer, thus ensuring their electrical properties. Using indacenodithiophene-co-benzothiadiazole (IDT-BT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8-BT) as example materials, 5 cm2 arrays were prepared with only minute size variations, which is extremely difficult to do using previously reported methods. According to 2D-GIXRD analysis, the molecules inside the nanowires mainly adopted face-on π-stacking crystallite arrangements. This is quite different from the mixed arrangement of thin films. Nanowire-based OFETs exhibited a high average hole mobility of 1.1 cm2 V−1 s−1 and good device uniformity, indicating the applicability of CFEJ printing as a potential batch manufacturing and integration process for high-performance, scalable polymer nanowire-based OFET circuits. This technique can be used to fabricate various polymer arrays, enabling the use of organic polymer semiconductors in large-area, high-performance electronic devices and providing a new path for the fabrication of flexible displays and wearable electronics in the future. [ABSTRACT FROM AUTHOR]

Large area and highly aligned polymer semiconductor sub-microwires were fabricated using the coaxial focused electrohydrodynamic jet printing technology. As indicated by the results, the sub-microwire arrays have smooth morphology, well reproducibility and controllable with a width of ~110 nm. Analysis shows that the molecular chains inside the sub-microwires mainly exhibited edge-on arrangement and the π-stacking direction (010) of the majority of crystals is parallel to the long axis of the sub-microwires. Sub-microwires based organic field effect transistors showed high mobility with an average of 1.9 cm2 V−1 s−1, approximately 5 times higher than that of thin film based organic field effect transistors. In addition, the number of sub-microwires can be conveniently controlled by the printing technique, which can subsequently concisely control the performance of organic field effect transistors. This work demonstrates that sub-microwires fabricated by the coaxial focused electrohydrodynamic jet printing technology create an alternative path for the applications of high-performance organic flexible device. Here, the authors fabricate large area and highly aligned polymer semiconductor sub-microwires arrays via coaxial focused electrohydrodynamic jet printing technology, achieving high on/off ratio and average mobility that is 5x higher than that of thin film based organic field effect transistors. [ABSTRACT FROM AUTHOR]

Bioinspired electronics have shown great potential in the field of artificial intelligence and brain‐like science. Low energy consumption and multifunction are key factors for its application. Here, multisensory artificial synapse and neural networks based on electrolyte‐gated vertical organic field‐effect transistors (VOFETs) are first developed. The channel length of the organic transistor is scaled down to 30 nm through cross‐linking strategy. Owing to the short channel length and extremely large capacitance of the electric double layer formed at the electrolyte–channel interface, the minimum power consumption of one synaptic event is 0.06 fJ, which is significantly lower than that required by biological synapses (1–10 fJ). Moreover, the artificial synapse can be trained to learn and memory images in a 5 × 5 synapse array and emulate the human brain's spatiotemporal information processing and sound azimuth detection. Finally, the artificial tongue is designed using the synaptic transistor that can discriminate acidity. Overall, this study provides new insights into realizing energy‐efficient artificial synapses and mimicking biological sensory systems. [ABSTRACT FROM AUTHOR]

Ambipolar polymer semiconductors are potentially serviceable for logic circuits, light-emitting field-effect transistors (LFETs) and polymer solar cells (PSCs). Although several high-performance ambipolar polymers have been developed, their optoelectronic devices are generally processed from toxic chlorinated solvents. To achieve the commercial applications of organic FETs (OFETs), the polymers should be processed from nonchlorinated solvents, instead of chlorinated solvents. However, most conjugated polymers show poor solubility in nonchlorinated solvents. It is of great importance to develop ambipolar polymers that can be processed from nonchlorinated solvents. Here, we develop a nonchlorinated solvent processed polymer named poly[7-fluoro-N, N′-di(4-decyltetradecyl)-7′-azaisoindigo-6′,6″-(thieno[3,2-b]thiophene-2,5-diyl)-7‴-fluoro-N″, N‴-di(4-decyltetradecyl)-7″-azaisoindigo-6,6‴-([2,2″-bithiophene]-5,5″-diyl)] (PITTI-BT) by designing a monomer with a large molar mass. The polymer displays good solubility in p-xylene (PX). Well-aligned films of PITTI-BT are achieved by an off-center spin-coating (SC) method. Based on the high-quality films, the OFETs fabricated from PX solution achieve record ambipolar performance with hole and electron mobilities of 3.06 and 2.81 cm2 V−1 s−1, respectively. The combination of nonchlorinated solvents and good alignment process offers an effective and eco-friendly approach to obtain high-performance ambipolar transistors. [ABSTRACT FROM AUTHOR]

Flexible electronics have suggested tremendous potential to shape human lives for more convenience and pleasure. Strenuous efforts have been devoted to developing flexible organic field-effect transistor (FOFET) technologies for rollable displays, bendable smart cards, flexible sensors and artificial skins. However, these applications are still in a nascent stage for lack of standard high-performance material stacks as well as mature manufacturing technologies. In this review, the material choice and device design for FOFET devices and circuits, as well as the demonstrated applications are summarized in detail. Moreover, the technical challenges and potential applications of FOFETs in the future are discussed. [ABSTRACT FROM AUTHOR]

Monolayer molecular crystals (MMC) of NDI3HU‐DTYM2 are grown on flexible substrates for constructing organic field effect transistors (OFET) as sensors to detect dimethoate. Benefitting from the ultra‐thin thickness of monolayer and highly crystalline nature, the MMC‐OFET based dimethoate sensors exhibit an ultrahigh detection limit of 0.60 ppb. The devices also show excellent conformal ability on various curved surfaces with negligible performance degradation. This work offers a promising flexible candidate for the fast and efficient detection of organophosphorus pesticides. [ABSTRACT FROM AUTHOR]

Realizing the reliable modulation of the carrier type and density in graphene is a challenging task, especially for epitaxial graphene (EG) grown in situ on SiC via thermal decomposition. In this process, doping is seldom adopted for substrate pretreatment, and the residual carriers in EG are determined by the properties of the SiC substrate and the random defects in EG. Here, we demonstrate a simple and effective technique for hole doping in EG on the Si-face of SiC (0001) implanted with boron ions. P-type EG with a carrier concentration of approximately 1–2 × 1012 cm−2 and a room-temperature mobility of 100–300 cm2/V s was achieved at the boron ion dose of approximately 1 × 1015 cm−2 at a centroid depth of approximately 140 nm from the SiC surface. These transport properties are comparable with the data reported for unintentionally doped P-type EG on the Si-face of SiC [Tedesco et al., Appl. Phys. Lett. 95, 122102 (2009)], for which the Hall device size was 40 times smaller compared to our device. The formation of P-type EG on the Si-face of SiC (0001) in this study was attributed to the synergetic effects of boron doping in EG and the transfer of electrons from EG into SiC. The detailed mechanisms are studied and discussed in this paper. The method demonstrated herein can be universally applied to downshift the Fermi level of EG on SiC, regardless of the crystallization orientation or polytype. The developed method is also compatible with modern semiconductor procedures. [ABSTRACT FROM AUTHOR]

Abstract Organic field-effect transistors (OFETs) have received significant interest due to potential applications from low-cost active circuit to wearable health care devices. Organic semiconductors as one of the key components in OFETs have drawn great attentions during last decades. Among them, antiaromatic and quinoidal materials have become the most intensively studied semiconductors. Therefore, this review describes the chemical structures and efficiency characteristics of π-conjugated materials through antiaromaticity and quinoid strategy for OFETs. In addition, rational designs and synthetic methods for these materials will be summarized, and a practical guideline for accelerating the development of high-performance semiconducting materials and devices will be provided. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) have received considerable attention across the world due to their potential applications in integrated circuits for large-area, flexible and low-cost electronics, and a series of breakthroughs in their research have been made in the past decade. Although numerous novel organic semiconductive materials with outstanding properties have been synthesized, the fabrication of OFETs and the investigation of amorphous polymer insulators (APIs) are attracting more and more research interest due to their significance in semiconductor growth, charge transport and device stability. In this review, an introduction to APIs and OFETs is given, and the following aspects are then successively discussed: commonly used APIs in OFETs, applications of API in high-performance OFETs, low-energy-consumption OFETs, functional OFETs, and self-healing OFETs. In the last section, a projection of some future trends for APIs in OFETs is presented. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis and characterizationoftwo new D-A-D molecules (E)-5,5′-bis(5-(benzo[b]thiophen-2-yl)thiophen-2-yl)-1,1′-bis(2-ethyl-hexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BTBPD) and (E)-5,5′-bis- (5-(benzo[b]furan-2-yl)thiophen-2-yl)-1,1′-bis(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BFBPD). They entail bipyrrolylidene-2,2′(1H,1′H)-dione (BPD, known as Pechmann dye) as theelectron-accepting core that is flanked by two benzo[b]thiophene moieties and two benzo[b]furan moieties,respectively. Crystal structures of BTBPDand BFBPDprovide solid evidence for the intermolecular donor–acceptor(D-A) interactions, which are favorable for improving charge transportperformance. Organic field-effect transistors (OFETs) were preparedbased on thin films of BTBPDand BFBPDthroughsolution-processed technique. OFETs of BTBPDexhibitrelatively high hole mobility up to 1.4 cm2V–1s–1with high on/off ratio up to 106. In comparison, the hole mobility of OFETs with BFBPD(0.14 cm2V–1s–1) is relatively low, because of the poor thin-film morphology andlow molecular ordering, even after annealing. Thin-film morphologicaland XRD studies were carried out to understand the variation of holemobilities after annealing at different temperatures. The presentstudies clearly demonstrate the potentials of BPDthatis planar and polar as the electron-acceptor moiety to build D-A moleculesfor organic semiconductors with good performance. [ABSTRACT FROM AUTHOR]

A diketopyrrolopyrrole–thiazolothiazole copolymer with a short π–π stacking distance (3.52 Å), due to the introduction of heteroaromatic rings, exhibits a high charge mobility above 3.40 cm2 V−1 s−1 at a relatively gentle annealing temperature. [ABSTRACT FROM AUTHOR]

Abstract: 2,6-Dialkylphenyldithieno[3,2-b:2′,3′-d]thiophene derivatives (DPCn–DTT) were synthesized and characterized. Effect of alkyl groups on optical characteristics, electrochemical properties, film-forming ability, and field-effect performance was studied. The four compounds DPCn–DTT show almost the same energy levels of the highest occupied molecular orbits and optical energy gaps, but they exhibit different charge carrier transport characteristics. The thin film transistors based on DPC1–DTT with the shortest alkyl groups (methyl groups) show the highest mobility of 0.54 cm2 V−1 s−1. Substrate temperature and surface modification of the SiO2 insulators have a remarkable effect on field-effect performance. High-quality microribbons of DPC8–DTT with octyl groups were prepared by a solution-phase self-assembly process. Single crystal field-effect transistors based on an individual DPC8–DTT microribbon exhibit a high mobility of 1.1 cm2 V−1 s−1 with a current on/off ratio of 6.5 × 104. [Copyright &y& Elsevier]

Two structural isomers of six-fused-ring sulfur-containing molecules were synthesized as active materials for p-type organic field-effect transistors, and their optical and electrochemical properties were characterized. Field-effect transistors based on these compounds were fabricated to investigate the relationships between structures and semiconductor properties. [ABSTRACT FROM AUTHOR]