Photoresponsive n-channel organic field-effect transistors based on a tri-component active layer

Photoresponsive OFETs were fabricated based on a tri-component active layer (NDI2OD-DTYM2, spiropyran and polystyrene). The results demonstrated that these OFETs displayed photoresponsive feature to alternate UV and vis light due to the photoisomerization of spiropyran between the closed-ring state and ionic open-ring state.     

High-performance organic field-effect transistors: molecular design, device fabrication, and physical properties

In the past decade, tremendous progress has been made in organic field-effect transistors (OFETs). Their real applications require further development of device performance. OFETs consist of organic semiconductors, dielectric layers, and electrodes. Organic semiconductors play a key role in determining the device characteristics. The properties of the organic semiconductors, such as molecular structure and packing, as well as molecular energy levels, can be properly controlled by molecular design. Therefore, we designed and synthesized a series of organic molecules. The synthesized organic semiconductors exhibit excellent field-effect properties due to strong intermolecular interactions and proper molecular energy levels. Meanwhile, the influence of the device fabrication process, organic semiconductor/dielectric layer interface, and organic layer/electrode contact on the device performance was investigated. A deep understanding of these factors is helpful to improve field-effect properties. Furthermore, single-crystal field-effect transistors are highlighted because the single-crystal-based FETs can provide an accurate conducting mechanism of organic semiconductors and higher device performance as compared with thin film FETs.     

Proteins as functional interlayer in organic field-effect transistor

The paper summarizes and discusses the recent advances of proteins as functional interlayers in organic field-effect transistors (OFETs). Specific focus is given on the proteins integrated into the device structure, either to act as dielectric materials or to perform as the functional interlayer between the dielectric and the organic semiconductor (OSC). The main emphasis is give to the location and the specific effect of protein layers in the structure of OFETs. Besides, the possibility of amyloid serving as useful building blocks for OFET is discussed.     

有机场效应晶体管应用于化学及生物传感的研究进展

有机场效应晶体管(OFETs)是以有机半导体材料作为有源层的晶体管器件。和传统的无机半导体器件相比,由于其具有成本低、易加工、柔性好和生物相容性而被人们广泛研究,在多种化学和生物传感器领域具有潜在而广泛的应用前景。本文简单介绍了OFETs的结构和工作原理,总结了近几年来OFETs在化学及生物传感方面的研究进展,最后对OFETs的发展方向做了归纳和展望。     

并五苯及其衍生物在有机场效应晶体管中的应用

有机场效应晶体管（organic field—effect transistors,OFETs）是以有机半导体材料作为有源层,通过电场控制电流的电子器件．与传统的无机半导体器件相比,由于其可应用于生产大面积、柔性、低成本电子设备而备受关注,在有机存储器件、有机太阳能电池、柔性平板显示和电子纸等众多领域具有潜在而广泛的应用前景．并苯类材料因其紧密的分子堆积及优异的半导体性能被广泛研究．其中,并五苯及其衍生物在场效应晶体管中表现出良好的性质,其效果甚至可以与非晶硅相媲美,但并五苯较差的溶解性及环境稳定性阻碍了其进一步应用．科研工作者通过对分子结构进行修饰改造设计,合成了一系列并五苯的衍生物,其不仅在稳定性、电学性能和溶解性方面有很大提高,还可以将该p-型半导体材料拓展到双极性及n-型半导体材料领域．本文对并五苯及其衍生物在有机场效应晶体管中的应用进行了较为全面的综述,期望对该领域的研究起到一定的推动作用．     

Synergistic Effects of Self-Assembled Monolayers in Solution-Processed 6,13-Bis(triisopropylsilylethynyl)Pentacene Transistors

Organic semiconductors are highly interface-sensitive, and therefore chemical functionalization using self-assembled monolayers (SAMs) is often adopted to tailor their properties. This study clarifies the synergistic effects of electrode and dielectric SAMs on the behavior of solution-processed organic field-effect transistors (OFETs). Utilization of a self-consistent device model enables a physically robust treatment of the measured electrical characteristics of the OFETs, thus providing highly reliable materials, interface, morphology, and transport parameters. These parameters are further extended and correlated to build a comprehensive picture on trap energy and injection-transport relationship, finally revealing a set of fundamental insights into chemically modified OFETs.     

Tailoring and patterning of dielectric interfaces for the development of advanced organic field-effect transistors

The progress of organic field-effect transistors (OFETs) has led to the advent of a new area of printed and/or flexible electronics. In organic transistors and circuits, the interface between a gate insulator (GI) and an organic semiconductor (OS) plays a critical role on the electrical performance together with the functionality, the reliability and the long-term stability. In this review, we describe the basic principles of engineering a variety of the GI/OS interfaces for the development of advanced OFETs from the framework of the surface morphology and the physico-chemical surface interactions. We also discuss the dielectric interface modification and the resultant device performance of the OFETs.     

Rational design of diarylethylene-based polymeric semiconductors for high-performance organic field-effect transistors

Constructing planar, rigid, and high electronically delocalized π-conjugated molecular system is the most basic requirements of obtaining high-performance polymeric semiconductors for organic field-effect transistors (OFETs). In this regard, diarylethylene (DAE)-based polymers show great potential because many substantive progresses related to polymer field-effect transistors had been achieved from the kind of polymer materials in recent years. In the brief review, series of DAE-based polymer are highlighted, based on which several design strategies have been summarized by the way of comparative research method. These strategies have important guiding significance not only for further developing new DAE-based and other polymeric semiconductors for OFETs but also for developing specific polymeric semiconductors for other organic electronics, such as organic photovoltaics and organic light-emitting diodes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 585–603     

Monolayer organic field-effect transistors

Monolayer organic field-effect transistors(OFETs) are attracting worldwide interest in device physics and novel applications due to their ultrathin active layer for two-dimensional charge transport. The monolayer films are generally prepared by thermal evaporation, the Langmuir technique or self-assembly process, etc., but their electrical performance is relatively lower than corresponding thick films. From 2011, the performance of monolayer OFETs has been boosted by using the monolayer molecular crystals(MMCs) as active channels, which opened up a new era for monolayer OFETs. In this review, recent progress of monolayer OFETs, including the preparation of monolayer films, their OFET performance and applications are summarized.Finally, perspectives of monolayer OFETs in the near future are also discussed.     

A highly pi-stacked organic semiconductor for field-effect transistors based on linearly condensed pentathienoacene

We present the synthesis and characterization of a fused-ring compound, dithieno[2,3-d:2',3'-d']thieno[3,2-b:4,5-b']dithiophene (pentathienoacene, PTA). In contrast to pentacene, PTA has a larger band gap than most semiconductors used in organic field-effect transistors (OFETs) and therefore is expected to be stable in air. The large pi-conjugated and planar molecular structure of PTA would also form higher molecular orders that are conductive for carrier transport. X-ray diffraction and atomic force microscopy experiments on its films show that the molecules stack in layers with their long axis upright from the surface. X-ray photoelectron spectroscopy suggests that there are no chemical bonds at the PTA/Au interface. OFETs based on the PTA have been constructed, and their performances as p-type semiconductors are also presented. A high mobility of 0.045 cm(2)/V s and an on/off ratio of 10(3) for a PTA OFET have been achieved, demonstrating the potential of PTA for application in future organic electronics.     

小分子场效应晶体管

近几年来,作为新一代半导体晶体管的有机场效应晶体管(OFET)在制备技术和器件性能上都取得了很大的进步,并引起了有机半导体领域研究人员的广泛关注。本文主要介绍了常见的小分子材料在场效应晶体管中的应用,并对几种有机小分子材料的结构和场效应性能做了总结。     

Protein Assays on Organic Electronics: Rational Device and Material Designs for Organic Transistor-Based Sensors

Artificial receptor-based protein assays have various attractive features such as a long-term stability, a low-cost production process, and the ease of tuning the target specificity. However, such protein sensors are still immature compared with conventional immunoassays. To enhance the application potential of synthetic sensing materials, organic field-effect transistors (OFETs) are some of the suitable platforms for protein assays because of their solution processability, durability, and compact integration. Importantly, OFETs enable the electrical readout of the protein recognition phenomena of artificial receptors on sensing electrodes. Thus, we believe that OFETs functionalized with artificial protein receptors will be a powerful tool for the on-site analyses of target proteins. In this Minireview, we summarize the recent progress of the OFET-based protein assays including the rational design strategies for devices and sensing materials.     

Ladder‐Type Heteroarene‐Based Organic Semiconductors

The fusion of heteroaromatic rings into ladder‐type heteroarenes can stabilize frontier molecular orbitals and lead to improved physicochemical properties that are beneficial for applications in various optoelectronic devices. Thus, ladder‐type heteroarenes, which feature highly planar backbones and well‐delocalized π conjugation, have recently emerged as a promising type of organic semiconductor with excellent device performance in organic photovoltaics (OPVs) and organic field‐effect transistors (OFETs). In this Focus Review, we summarize the recent advances in ladder‐type heteroarene‐based organic semiconductors, such as hole‐ and electron‐transporting molecular semiconductors, and fully ladder‐type conjugated polymers towards their applications in OPVs and OFETs. The recent use of ladder‐type small‐molecule acceptor materials has strikingly boosted the power conversion efficiency of fullerene‐free solar cells, and selected examples of the latest developments in ladder‐type fused‐ring electron acceptor materials are also elaborated.     

Angular-shaped naphthalene tetracarboxylic diimides for n-channel organic transistor semiconductors

A series of compounds based on the angular-shaped naphthalene tetracarboxylic diimide core have been synthesized, characterized and used as active layers of organic field-effect transistors (OFETs). The fabricated OFET devices exhibit n-type semiconducting characteristics, demonstrating the first examples of semiconductors based on angular-shaped naphthalene tetracarboxylic diimides.     

Current versus gate voltage hysteresis in organic field effect transistors

Abstract  Research into organic field effect transistors (OFETs) has made significant advances—both scientifically and technologically—during the last decade, and the first products will soon enter the market. Printed electronic circuits using organic resistors, diodes and transistors may become cheap alternatives to silicon-based systems, especially in large-area applications. A key parameter for device operation, besides long term stability, is the reproducibility of the current–voltage behavior, which may be affected by hysteresis phenomena. Hysteresis effects are often observed in organic transistors during sweeps of the gate voltage (V _GS). This hysteresis can originate in various ways, but comparative scientific investigations are rare and a comprehensive picture of “hysteresis phenomena” in OFETs is still missing. This review provides an overview of the physical effects that cause hysteresis and discusses the importance of such effects in OFETs in a comparative manner. Graphical abstract        

有机场效应晶体管和分子电子学研究进展

近几年来,有机场效应晶体管在材料和器件方面都取得了长足的进展,成为分子电子学的一个重要方向。本文从有机半导体材料设计、有机半导体器件的构筑、单分子电子器件和纳米管在电子器件中的应用等方面,简单综述了有机场效应晶体管和分子电子学的最新研究进展。     

Solution-Processable Unsymmetrical Triarylamines: Towards High Mobility and ON/OFF Ratio in Bottom-Gated OFETs

Self-assembly of organic small molecules into an ordered thin film has been the key strategy towards efficient charge transport for organic field-effect transistors (OFETs). Solution processing is a feasible and economic way to enhance pi–pi interaction. Herein, nitrile-substituted unsymmetrical triarylamines for OFET applications with high mobility are reported. The compounds were constructed by Suzuki cross-coupling reactions under inert conditions. The HOMO level of about 5.3 eV indicates good hole-transporting ability. OFETs were assembled in bottom-gate, top-contact architecture. Devices fabricated from a binary solvent system exhibited excellent p-channel characteristics, with impressively high charge-carrier mobility of up to 2.58 cm² V⁻¹ s⁻¹ and I_ON/OFF current ratios of 10⁶–10⁷. SEM and AFM analysis showed the efficient molecular self-assembly attained by the simple and effective solvent-engineering method. Theoretical insights obtained by DFT calculations supported by single-crystal structures showed that the crystalline nature and packing modes of these compounds ensure high mobility. The results prove that these compounds have great potential for use in numerous electronic applications, such as sensors and logic switches.     

Organic semiconductors for solution-processable field-effect transistors (OFETs)

The cost-effective production of flexible electronic components will profit considerably from the development of solution-processable, organic semiconductor materials. Particular attention is focused on soluble semiconductors for organic field-effect transistors (OFETs). The hitherto differentiation between "small molecules" and polymeric materials no longer plays a role, rather more the ability to process materials from solution to homogeneous semiconducting films with optimal electronic properties (high charge-carrier mobility, low threshold voltage, high on/off ratio) is pivotal. Key classes of materials for this purpose are soluble oligoacenes, soluble oligo- and polythiophenes and their respective copolymers, and oligo- and polytriarylamines. In this context, micro- or nanocrystalline materials have the general advantage of somewhat higher charge-carrier mobilities, which, however, could be offset in the case of amorphous, glassy materials by simpler and more reproducible processing.     

Attaching organic semiconductors to gate oxides: in situ assembly of monolayer field effect transistors

This study unveils a new tetracene derivative that forms dense, upright monolayers on the surface of aluminum oxide. These monolayers spontaneously self-organize into the active layer in nanoscale field-effect transistor devices when aluminum oxide is used as the dielectric layer. This method gives high yields of working devices that have source-drain distances that are less than 60 nm, thereby providing a method to electrically probe the monolayer assemblies formed from approximately 10 zeptomoles of material (approximately 104 molecules). Moreover, this study delineates a new avenue for research in thin-film organic transistors where the active molecules are linked to the dielectric surface to form a monolayer transistor.     

Air-stable n-type organic field-effect transistors based on solution-processable, electronegative oligomers containing dicyanomethylene-substituted cyclopenta[b]thiophene

Solution-processable, electronegative, π-conjugated systems containing dicyanomethylene-substituted cyclopenta[b]thiophene were synthesized as potential active materials for air-stable n-type organic field-effect transistors (OFETs). Electrochemical measurements revealed that these compounds exhibited electrochemical stability and that the lowest unoccupied molecular orbital (LUMO) had an energy level less than -4.0 eV. Flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements were performed, and the value of intradomain electron mobility was determined to be as high as 0.1 cm(2) V(-1) s(-1) . The OFETs were fabricated by spin-coating thin films of the compounds as an active layer. The electron mobility of the OFETs was 3.5×10(-3) cm(2) V(-1) s(-1) in vacuum. Furthermore, electron mobility of the same order of magnitude and stable characteristics were obtained under air-exposed conditions. X-ray diffraction measurements of the spin-coated thin films revealed the difference of molecular arrangements depending on the inner conjugated units. Atomic force microscopy measurements of crystalline-structured films exhibited the formation of grains. The accomplishment of air-stability was attributed to the combined effect of the low-lying LUMO energy level and the molecular arrangements in the solid state, avoiding both the quenching of electron carriers and the intrusion of oxygen and/or moisture.