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Covalent organic frameworks (COFs) are a type of crystalline porous polymer composed of light elements through strong covalent bonds. COFs have attracted considerable attention due to their unique designable structures and excellent material properties. Currently, COFs have shown outstanding potential in various fields, including gas storage, pollutant removal, catalysis, adsorption, optoelectronics, and their research in the sensing field is also increasingly flourishing. In this review, we focus on COF‐based sensors. Firstly, we elucidate the fundamental principles of COF‐based sensors. Then, we present the primary application areas of COF‐based sensors and their recent advancements, encompassing gas, ions, organic compounds, and biomolecules sensing. Finally, we discuss the future trends and challenges faced by COF‐based sensors, outlining their promising prospects in the field of sensing. [ABSTRACT FROM AUTHOR]

Y‐series non‐fullerene acceptors (NFAs) have achieved great progress in organic solar cells (OSCs). Most research attention is currently paid to their molecular engineering to improve the efficiency of OSCs. However, as n‐type organic semiconductors, the relationship between their molecular packing structures and charge transport properties is mostly ignored. Herein, it is clarified how the molecular packing of Y‐series NFAs fundamentally determines their charge transport properties by manipulating their crystal stacking via sidechain engineering. Therefore, branched alkyl/alkoxy substitutions are taken on a reference NFA (Y6‐1O), affording three derivatives, namely 1OBO‐1, 1OBO‐2, and 1OBO‐3. Results show that while the replacement of branched alkyl/alkoxy sidechains has little impact on optical properties and energy levels, it can change crystal stacking motifs significantly. The single crystal of Y6‐1O with all linear sidechains forms a 2D‐brickwork structure and shows lower mobility. In contrast, 1OBO‐2 with all branched sidechains exhibits a favorable 3D interpenetrating porous network, displaying an electron mobility of 1.42 cm2 V−1 s−1 in single‐crystal organic field‐effect transistors (SC‐OFETs). This value is among the highest for NFA‐based n‐type OFETs. This study not only reveals the fundamental structure–property relationships of Y‐series NFAs, but also suggests the potential of Y‐series NFAs for high‐performance n‐type organic semiconductors. [ABSTRACT FROM AUTHOR]

Carbon nanorings (CNRs) and carbon nanobelts (CNBs) of various sizes and innovative molecular architectures have ushered improvement in research in recent years. This serves as a prerequisite for further advances and applications, such as organic semiconductors and bottom‐up synthesis of single‐walled carbon nanotubes. Nevertheless, challenges such as high strain energy, excessive reactivity, end‐product stability, low‐scale yields, and side reactions inhibit material synthesis and applications. In this review, CNRs, CNBs, and other heteroatom‐doped molecular belts are discussed based on their molecular structural characteristics, with a special focus on their developments in the past two years. Furthermore, current applications, research obstacles, and future developments related to CNRs and CNBs are discussed. For the first time, studies and advancements in organic field‐effect transistors (OFETs) have been summarized in detail. [ABSTRACT FROM AUTHOR]

A family of novel highly π‐extended tetracyano‐substituted acene diimides, named as tetracyanodiacenaphthoanthracene diimides (TCDADIs), have been synthesized using a facile four‐fold Knoevenagel condensation strategy. Unlike conventional cyano substitution reactions, our approach enables access to a large π‐conjugated backbone with the in‐situ formation of four cyano substitutents at room temperature while avoiding extra cyano‐functionalization reactions. TCDADIs decorated with different N‐alkyl substituents present good solubility, near‐coplanar backbones, good crystallinity, and low‐lying lowest unoccupied molecular orbital energies of −4.33 eV, all of which contribute to desirable electron‐transport performance when applied in organic field‐effect transistors (OFET). The highest electron mobility of an OFET based on a 2‐hexyldecyl‐substituted TCDADI single crystal reaches 12.6 cm2 V−1 s−1, which is not only among the highest values for the reported n‐type organic semiconductor materials (OSMs) but also exceeds that of most n‐type OSMs decorated with imide units. [ABSTRACT FROM AUTHOR]

A family of novel highly π‐extended tetracyano‐substituted acene diimides, named as tetracyanodiacenaphthoanthracene diimides (TCDADIs), have been synthesized using a facile four‐fold Knoevenagel condensation strategy. Unlike conventional cyano substitution reactions, our approach enables access to a large π‐conjugated backbone with the in‐situ formation of four cyano substitutents at room temperature while avoiding extra cyano‐functionalization reactions. TCDADIs decorated with different N‐alkyl substituents present good solubility, near‐coplanar backbones, good crystallinity, and low‐lying lowest unoccupied molecular orbital energies of −4.33 eV, all of which contribute to desirable electron‐transport performance when applied in organic field‐effect transistors (OFET). The highest electron mobility of an OFET based on a 2‐hexyldecyl‐substituted TCDADI single crystal reaches 12.6 cm2 V−1 s−1, which is not only among the highest values for the reported n‐type organic semiconductor materials (OSMs) but also exceeds that of most n‐type OSMs decorated with imide units. [ABSTRACT FROM AUTHOR]

The emulation of functions and behaviors of biological synapses using electronic devices has inspired the development of artificial neural networks (ANNs) in biomedical interfaces. Despite the achievements, artificial synapses that can be selectively responsive to non‐electroactive biomolecules and directly operate in biological environments are still lacking. Herein, we report an artificial synapse based on organic electrochemical transistors and investigate the selective modulation of its synaptic plasticity by glucose. The enzymatic reaction between glucose and glucose oxidase results in long‐term modulation of the channel conductance, mimicking selective binding of biomolecules to their receptors and consequent long‐term modulation of the synaptic weight. Moreover, the device shows enhanced synaptic behaviors in the blood serum at a higher glucose concentration, which suggests its potential application in vivo as artificial neurons. This work provides a step towards the fabrication of ANNs with synaptic plasticity selectively mediated by biomolecules for neuro‐prosthetics and human‐machine interfaces. [ABSTRACT FROM AUTHOR]

Although the effects of electron‐deficient group substitution on isoindigo on the corresponding conjugated polymers are extensively studied, the modification of isoindigo core with electron‐rich groups has not been investigated. It is envisioned that the introduction of the methoxy group on isoindigo will not only tune the highest occupied molecular orbital (HOMO) energy level of the corresponding polymers but also introduce O···S "conformation lock" to increase the coplanarity of the polymers, which should facilitate hole transport. Herein, the syntheses of two methoxylated isoindigos and the investigations on the charge transport behaviors of their copolymers with bisthiophene (2T) and bisthiazole (2Tz) are reported. It is found that the substitution positions have a drastic influence on the UV–vis absorption and electrochemical properties for both monomers and polymers. Theoretical calculations and single crystal structure analysis confirm the existence of O···S "conformation lock", however, both methoxy substitutions also change the aggregation behaviors of the corresponding polymers to a mixed face‐on/edge‐on orientation which has an adverse effect for charge transport. Among the four polymers, the polymer of 5,5'‐methoxylated isoindigo and 2T exhibit the best hole mobility of 1.9 × 10−1 cm2 V−1 s−1. [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]

Ladder‐like aromatic diketones (LADK), which possess a coplanar π‐extended geometry, a high electron deficiency as well as various attractive optoelectronic properties, are demonstrated as the promising candidates in building small‐molecule organic electron‐transporting materials, yet reports on direct integration of these structural motifs into n‐type polymers are rarely accessed. Herein, it is demonstrated that a possibility of realizing unipolar n‐type characteristics of such acceptor system by developing two novel donor–acceptor type polymers, in which the newly developed LADK unit, named as 3,8‐bis(2‐decyltetradecyl)‐5,10‐difluoro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐4,9‐dione (FIDTO‐R), is adopted as the acceptor segments. The resulting polymers present deep‐lying unoccupied molecular orbital levels (as low as −3.84 eV), compact π–π stacking (d‐spacing, ≈3.57 Å) coupled with uniform nanofiber‐like surface morphology. All these factors contribute to excellent unipolar n‐type characteristics with high electron mobilities of 0.27 and 1.01 cm2 V−1 s−1, together with high inverter gain values of 141 and 80, respectively. The recorded values are among the best in n‐type polymer field‐effect transistors and associated inverter circuits. These findings unambiguously reveal that the as‐prepared FIDTO‐R and its analog LADK derivatives are another type of excellent building blocks for the construction of high‐mobility n‐type polymers. [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]

Organic field‐effect transistor (OFET)‐based circuits require stable device performance. However, OFETs are suffering from process variation and environmental instability, which limits circuit performance. Here, an optimally designed XOR gate based on p‐type‐only OFETs is reported. The circuit has excellent postfabrication tunability that is enough to cope with a threshold voltage shift as high as 1.5 V. Moreover, the circuit largely reduces the number of transistors by 81% compared with conventional design and can realize ultralow power consumption. In addition, the XOR gate can act as a programmable inverter with good regenerative property. Utilizing the XOR gate, the authors demonstrate its application in cryptography. A 3481‐bit message is correctly encrypted and decrypted with an accuracy rate of up to 98.5%. The authors' work enables the accurate prediction of circuit operation in the presence of OFET threshold voltage shifts. [ABSTRACT FROM AUTHOR]

Cu‐benzenehexathiol (Cu‐BHT) has attracted significant attention due to its record high electrical conductivity and crystal defects Cu2c. However, the nonporous structure and small specific surface area of Cu‐BHT with two‐dimensional kagome lattice invariably limit its practical application in sensing and catalysis. In this work, Cu‐BHT nanotubes (Cu‐BHT‐NTs) are designed and prepared via a facile homogeneous reaction to solve these problems. Compared with the traditional nanorod‐like structure, the Cu‐BHT‐NTs not only have a higher specific surface area but also possess a higher proportion of crystal defects (66.6%). The successfully configured DPPTT/Cu‐BHT‐NTs heterostructure organic field‐effect transistor (OFET)‐based sensor exhibits excellent sensitivity as high as 13 610%, a minimum detection limits down to 5 ppb, and exceptional selectivity to nitric oxide (NO) toxic gases. Theoretical analysis systematically shows that Cu2c sites in the Cu‐BHT‐NTs increase the number of electrons transferred from the heterostructure to NO molecules, confirming that the high sensitivity and selectivity result from the high binding between Cu‐BHT‐NTs and NO molecules. Furthermore, a fully flexible device based on the heterojunction OFET sensor is prepared to ensure the convenience of wearing and carrying gas sensors, opening up a new avenue for the next generation of wearable intelligent electronics. [ABSTRACT FROM AUTHOR]

The molecular packing and resultant charge transport behaviors of semiconducting polymers are widely known to be temperature‐dependent. Due to the limitation of measurement methods, previous studies on molecular packing behavior have been mainly focused on a very limited temperature range, and therefore cannot support the understanding of charge transport behaviors. In this study, with a homemade temperature‐dependent grazing incidence XRD measurement chamber, the relationship between molecular packing structure and charge transport properties of diketopyrrolopyrrole‐based polymers is investigated across a wide temperature range of 98–623 K. Glass transition temperatures of the alkyl side‐chain and aromatic backbone are identified through the observation of clear transitions in the thermal expansion coefficients of d−d packing and π−π stacking, respectively. A correlation between the π−π stacking distance and charge transport properties is then established using an extended Miller−Abrahams model. The turning point of the charge transport and the failure of the polymer‐based devices are proved to be caused by packing structure changes due to increased temperatures. Such an examination over a wide range of temperatures improves the understanding of the charge transport properties of semiconducting polymers and helps construct thermally stable devices to be used in extreme conditions. [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]

D‐A conjugated polymers P1 and P2 are synthesized by copolymerizing bisthiophene‐fused diketopyrrolopyrrole (4,11‐bis(2‐decyltetradecyl)‐7H,14H‐thieno[3',2':7,8]‐indolizino[2,1‐a]thieno[3,2‐g]indolizine‐7,14‐dione, BTI) with terthiophene and thiophene‐benzothiadiazole‐thiophene, respectively. Molecular packing is characterized by X‐ray diffraction. The film morphology is characterized by atomic force and scanning electron microscopy. The vertical phase separation is characterized by XPS. The mechanism of film morphology formation is explained from intermolecular interaction, kinetics, and surface free energy. The spin‐coated films of polymers blended with PC71BM are served as semiconductor layers in near‐infrared (NIR) phototransistors. The impact of morphology on optoelectronic performance is analyzed. The mobility of organic field effect transistors based on P1 or P2 thin films remains constant with the addition of PC71BM with weight ratio being less than 50%. The main reason is that π–π stacking in both P1 and P2 thin films is at all directions and PC71BM does not disturb the charge percolation path. Benzothiadiazole in P2 enables stronger mutual attraction between P2 and PC71BM, and therefore large contact area between P2 and PC71BM forms in the heterojunction. The photoresponsivity improves by 2 times for NIR phototransistors based on P2/PC71BM when decreasing light intensity from 63 to 1.8 µW cm‐2. The above results suggest a feasible conjugated polymer design rule for high sensitivity NIR phototransistors. [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]

The cornerstones of emerging high-performance organic photovoltaic devices are bulk heterojunctions, which usually contain both structure disorders and bicontinuous interpenetrating grain boundaries with interfacial defects. This feature complicates fundamental understanding of their working mechanism. Highly-ordered crystalline organic p–n heterojunctions with well-defined interface and tailored layer thickness, are highly desirable to understand the nature of organic heterojunctions. However, direct growth of such a crystalline organic p–n heterojunction remains a huge challenge. In this work, we report a design rationale to fabricate monolayer molecular crystals based p–n heterojunctions. In an organic field-effect transistor configuration, we achieved a well-balanced ambipolar charge transport, comparable to single component monolayer molecular crystals devices, demonstrating the high-quality interface in the heterojunctions. In an organic solar cell device based on the p–n junction, we show the device exhibits gate-tunable open-circuit voltage up to 1.04 V, a record-high value in organic single crystalline photovoltaics. Realizing organic p–n junctions based on ordered crystalline materials with dimensions comparable to the exciton diffusion length of most organic semiconductors remains a challenge. Here, the authors report a strategy to form molecular monolayer crystal-based p–n junctions with thickness below 5 nm. [ABSTRACT FROM AUTHOR]

A heterocycloarene derivative (S-Octulene) possessing two sulfur atoms was conveniently synthesized through Bi(OTf)3-catalyzed cyclization from a macrocyclic tetramethoxyethenylated precursor. The physical properties of S-Octulene and its supramolecular host–guest interaction with C60 and C70 were investigated by fluorescence titration and 1H NMR. The solution-processed organic field-effect transistor (OFET) measurements demonstrated that S-Octulene behaved as a p-type semiconductor with a hole mobility exceeding 0.01 cm2 V−1 s−1. Our findings pave a new path to design novel heterocycloarenes for the development of host–guest chemistry and organic semiconductors. [ABSTRACT FROM AUTHOR]

The sensitivity of conventional thin‐film OFET‐based sensors is limited by the diffusion of analytes through bulk films and remains the central challenge in sensing technology. Now, for the first time, an ultrasensitive (sub‐ppb level) sensor is reported that exploits n‐type monolayer molecular crystals (MMCs) with porous two‐dimensional structures. Thanks to monolayer crystal structure of NDI3HU‐DTYM2 (NDI) and controlled formation of porous structure, a world‐record detection limit of NH3 (0.1 ppb) was achieved. Moreover, the MMC‐OFETs also enabled direct detection of solid analytes of biological amine derivatives, such as dopamine at an extremely low concentration of 500 ppb. The remarkably improved sensing performances of MMC‐OFETs opens up the possibility of engineering OFETs for ultrasensitive (bio)chemical sensing. [ABSTRACT FROM AUTHOR]

Heteroacenes containing a dihydropyrrolo[3,2‐b]pyrrole core such as 5,10‐dihydroindolo[3,2‐b]indole (DBPP) and dinaphtho [2,3‐b:2',3'‐f]pyrrolo[3,2‐b]pyrrole(DNPP) are potential p‐type semiconductors for organic field‐effect transistors (OFETs) owing to their electron‐rich and easy‐to‐modify core structure. Here we report that how the structural variations such as ring fusion pattern, heteroatom introduction and chlorination influence the crystallinity, orientation and morphology of this type of heteroacenes hence their OFET performance. It is revealed that angular fused C8‐iso‐DNPP has a higher HOMO energy level with matches better with the work‐function of Au and shows better crystallinity and more uniformed morphology compared to the linearly fused isomer C8‐DNPP. Thus it exhibits very similar hole mobility to C8‐DNPP but much smaller threshold voltages. On the other hand, the introduction of extra N atoms into DNPP affords an analogue DQPP and greatly alters the orientation of the crystalline film from "edge‐on" to "face‐on", which results in a two‐order decrease of the hole mobility. Our result also shows that heavily chlorinated DBPP (TClDBPP) leads to the completely loss of the hole transport capability due to the large π‐π distance imposed by the large chlorine atoms. [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]

Benzopyrazinoisoindigo, a pigment reported 40 years ago, should be a good candidate for n-type semiconductors if the reported structure is correct. Reinvestigation of this molecule revealed that it is actually (4 H,4′ H)-benzopyrazinoisoindigo, which could be considered as the reduced form of benzopyrazinoisoindigo, and hence, it is a good candidate for p-type semiconductors. The route toward the synthesis of this molecule was optimized, and a mechanism was accordingly proposed. A field-effect transistor based on this material showed a hole mobility up to 2.5 × 10-2 cm2 V-1 s-1. [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]

The mismatch of energy alignment of low‐cost metals with organic semiconductors requires interfacial modification of the electrodes in organic field‐effect transistors (OFETs). However, traditional methods involve chemicals and operations that introduce potential contaminations or damages to the device, which deteriorate the device performance. Here, an inner‐evaporator modification method using ultrathin polyporphyrin film (≈1.1 nm) as the interlayer between semiconductor and Ag or Cu electrode is developed. Both the modification and device fabrication are processed simultaneously in the high‐vacuum environment of the thermal evaporator. After the contamination‐free modification, the contact resistance decreases by 2–3 orders of magnitude, and the field‐effect mobility of pentacene is one of the highest values among pentacene thin‐film bottom‐contact OFETs based on modified Ag/Cu electrodes, comparable to that of modified Au electrodes. Owing to its simplicity, efficiency in improving device performance, and compatibility with OFET fabrication process, this method has great potential for application in future organic electronics with low‐cost metal electrodes. [ABSTRACT FROM AUTHOR]

Their mismatched energy alignment with organic semiconductors limits the application of low‐cost metals in organic electronics. A novel surface catalytic low‐temperature chemical vapor deposition (CVD) based on the Ullmann reaction is applied to selectively modify patterned Ag/Cu electrodes. The work functions of Ag and Cu are tuned from 4.3 and 4.5 eV to 4.8 and 4.9 eV, respectively, after modification with conjugated polymers. Owing to the change in work function and pentacene morphology, the contact resistance decreases by several orders of magnitude compared with that of devices with pristine Ag or Cu electrodes, and the correspond mobilities of pentacene bottom‐contact field effect transistors increase to 0.66 cm2 V−1 s−1 (Ag) and 0.64 cm2 V−1 s−1 (Cu). This mobility is one of the highest values demonstrated with pentacene organic field‐effect transistors with Cu or Ag electrodes. This simple, clean, and low‐temperature modification method paves the way for the application of low‐cost metals in organic electronics. [ABSTRACT FROM AUTHOR]

A family of novel highly π‐extended tetracyano‐substituted acene diimides, named as tetracyanodiacenaphthoanthracene diimides (TCDADIs), have been synthesized using a facile four‐fold Knoevenagel condensation strategy. Unlike conventional cyano substitution reactions, our approach enables access to a large π‐conjugated backbone with the in‐situ formation of four cyano substitutents at room temperature while avoiding extra cyano‐functionalization reactions. TCDADIs decorated with different N‐alkyl substituents present good solubility, near‐coplanar backbones, good crystallinity, and low‐lying lowest unoccupied molecular orbital energies of −4.33 eV, all of which contribute to desirable electron‐transport performance when applied in organic field‐effect transistors (OFET). The highest electron mobility of an OFET based on a 2‐hexyldecyl‐substituted TCDADI single crystal reaches 12.6 cm2 V−1 s−1, which is not only among the highest values for the reported n‐type organic semiconductor materials (OSMs) but also exceeds that of most n‐type OSMs decorated with imide units. [ABSTRACT FROM AUTHOR]

A family of novel highly π‐extended tetracyano‐substituted acene diimides, named as tetracyanodiacenaphthoanthracene diimides (TCDADIs), have been synthesized using a facile four‐fold Knoevenagel condensation strategy. Unlike conventional cyano substitution reactions, our approach enables access to a large π‐conjugated backbone with the in‐situ formation of four cyano substitutents at room temperature while avoiding extra cyano‐functionalization reactions. TCDADIs decorated with different N‐alkyl substituents present good solubility, near‐coplanar backbones, good crystallinity, and low‐lying lowest unoccupied molecular orbital energies of −4.33 eV, all of which contribute to desirable electron‐transport performance when applied in organic field‐effect transistors (OFET). The highest electron mobility of an OFET based on a 2‐hexyldecyl‐substituted TCDADI single crystal reaches 12.6 cm2 V−1 s−1, which is not only among the highest values for the reported n‐type organic semiconductor materials (OSMs) but also exceeds that of most n‐type OSMs decorated with imide units. [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]

Ambipolar field-effect transistors based on polymer semiconductors facilitate the convenient fabrication of low-power complementary organic circuits. However, the species of ambipolar polymer semiconductors are limited; the design and synthesis strategies are scarce. This work demonstrated that bisthiophene-fused diketopyrrolopyrrole (DPPFu) was a wonderful building unit for ambipolar polymer semiconductors. Ambipolar polymer semiconductors could be obtained by copolymerizing DPPFu with both electron-deficient comonomers and electron-rich comonomers. P(DPPFu-T), P(DPPFu-TT) and P(DPPFu-BT) were synthesized by copolymerizing DPPFu with thiophene, thienothiophene and benzothiadiazole, respectively. The structural variation of comonomers allowed for a systematic study on the relationship between comonomer structure, frontier orbital energy level, orbital delocalization index, molecular packing, film morphology and the corresponding charge transport properties. Thienothiophene endowed P(DPPFu-TT) with maximum orientation of edge-on packing. The considerable delocalization extent of the lowest unoccupied molecular orbitals (LUMOs) for P(DPPFu-T) and P(DPPFu-TT) resulted in pronounced electron transport property. P(DPPFu-TT) displayed the best charge transport property with hole mobility up to about 0.1 cm2V−1s−1 and electron mobility of 7.5 × 10−2 cm2V−1s−1. P(DPPFu-BT) showed ideally balanced charge carrier mobilities for both holes and electrons of 1.6 × 10−2 cm2V−1s−1 and 1.7 × 10−2 cm2V−1s−1, respectively. Ion/Ioff ratios of all the ambipolar polymers were above 103. The ambipolarity of polymer semiconductors was related to not only push-pull electronic characteristics of comonomers, but also the planarity of polymer backbones and delocalization extent of frontier orbitals. Overall, this study provides valuable insights into the design and synthesis of ambipolar polymer semiconductors, which is crucial for the advancement of low-power complementary organic circuits. All the polymer semiconductors exhibited prominent ambipolar charge transport property. P(DPPFu-TT) displayed the best charge transport property and P(DPPFu-BT) showed ideally balanced charge carrier mobilities for both holes and electrons. Relationships between comonomer structure, frontier orbital energy level, orbital delocalization index, molecular packing, film morphology and the corresponding charge transport properties were investigated systematically. [Display omitted] • A series of ambipolar polymer semiconductors based on DPPFu were designed and successfully synthesized. • DFT calculations were employed to predict the physical characteristics of the ambipolar polymer semiconductors • Relationships between molecular packing, film morphology and charge transport properties were investigated systematically. • The hole and electron mobility of P(DPPFu-TT) were found to reach approximately 0.1 and 7.5×10-2 cm2V–1s–1, respectively. [ABSTRACT FROM AUTHOR]

The article offers information on the organic field-effect transistors (OFET) devices. It is mentioned that OFET devices are made by sublimiting the molecule thickness followed by the deposition of gold to define the electrodes. Also, silicon oxide deposition is carried out on OFET before the deposition of gold. Additionally nuclear magnetic resonance was conducted by using the Bruker 300 MHz spectrometer. Information on the use of the film cyclic voltammetry is presented.

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]

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]

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]

A series of new n-type copolymers based on perylene diimide(PDI) or naphthalene diimide (NDI) and phenothiazine (PTZ) with differentside chain length and molecular weight have been designed and synthesizedby Pd-catalyzed Suzuki coupling polymerization with or without phase-transfercatalyst Aliquat 336. The effects of main chain, side chain, and molecularweight on the thermal, optical, electronic, and charge transport propertiesof the polymers have been investigated. Aliquat 336 improves molecularweight as well as reduces polydispersity index of the polymers. Allthe polymers exhibit a broad absorption extending from 300 to 900nm. The main chain and side chain structure and molecular weight haveminor effects on the HOMO (−5.8 to −5.9 eV) and LUMO(−3.7 to −3.8 eV) levels of the polymers. n-Channelfield-effect transistors with bottom-gate top-contact geometry basedon these copolymers exhibit electron mobilities as high as 0.05 cm2V–1s–1and on/off ratiosas high as 105in nitrogen, which are among the best reportedfor rylene diimide-based polymers under the same test conditions. [ABSTRACT FROM AUTHOR]

Abstract: A solution-based transparent polymer was investigated as the gate dielectric for organic field-effect transistors (OFETs). Organic thin films (400nm) are readily fabricated by spin-coating a polyhydrazide solution under ambient conditions on the ITO substrates, followed by annealing at a low temperature (120°C). The smooth transparent dielectrics exhibited excellent insulating properties with very low leakage current densities of ∼10−8 A/cm2. High performance OFETs with evaporated pentacene as organic semiconductor function at a low operate voltage (−15V). The mobility could reach as high as 0.7cm2/Vs and on/off current ratio up to 104. Solution-processed TIPS-pentacene OFETs also work well with this polymer dielectric. [Copyright &y& Elsevier]

Abstract: A novel alternating D–A copolymer, PPor–BT, with dioctylporphyrin (Por) as a donor unit and 5,6-bis(octyloxy)benzo-2,1,3-thiadiazole (BT) as an acceptor unit, was designed and synthesized by Pd-catalyzed Sonogashira-coupling reaction. The copolymer showed good solubility and film-forming ability. PPor–BT exhibited a broad absorption band from 350 to 950 nm with two peaks centered at 456 and 818 nm corresponding to the Soret band and Q-bands absorption of porphyrin segments, respectively. The employment of electron deficient BT unit to construct donor-acceptor structure observably broadened the absorption spectrum and enhanced the Q-band absorption of the porphyrin-based polymer. The HOMO and LUMO energy levels of the polymer are −5.06 eV and −3.63 eV, respectively. The solution-processed organic field-effect transistors (OFETs) were fabricated with bottom gate/top-contact geometry. The mobility of PPor–BT based OFEFs reached 4.3 × 10−5 cm2 V−1 s−1 with an on/off current ratio of 104. This mobility is among the highest values for porphyrin-based polymers. [Copyright &y& Elsevier]

Abstract: A new conjugated polymer, poly(3,6-dihexyl-thieno[3,2-b]thiophenyl-2,5-diyl-alt-2,5-di(2-ethylhexyl)-3,6-bis(thien-2,5-diyl)-pyrrolo[3,4-c]-pyrrole-1,4-dione) (DH-PTTDPP) was synthesized by Pd-catalyzed Stille-coupling method. The thermal, absorption, electrochemical, photovoltaic properties, and field-effect charge transport of the polymer were examined. The polymer is soluble in common organic solvents and possesses a broad absorption band covering from 500nm to 900nm with an optical bandgap of 1.33eV. Field-effect transistors (FETs) based on DH-PTTDPP thin film showed a hole mobility of 2.5×10−3 cm2 V−1 s−1 with an on/off ratio of 105, which is among the high values for the conjugated polymers. Polymer solar cells (PSCs) based on DH-PTTDPP/PC70BM (1:1.5, w/w) demonstrated a power conversion efficiency of 1.90% under the illumination of AM 1.5, 100mWcm−2. These results indicate that DH-PTTDPP is an attractive polymer semiconductor for the applications in FETs and PSCs. [Copyright &y& Elsevier]