Huanli Dong

Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics

Since the discovery of highly conducting polyacetylene by Shirakawa, MacDiarmid, and Heeger in 1977, π-conjugated systems have attracted much attention as futuristic materials for the development and production of the next generation of electronics, that is, organic electronics. Conceptually, organic electronics are quite different from conventional inorganic solid state electronics because the structural versatility of organic semiconductors allows for the incorporation of functionality by molecular design. This versatility leads to a new era in the design of electronic devices. To date, the great number of π-conjugated semiconducting materials that have either been discovered or synthesized generate an exciting library of π-conjugated systems for use in organic electronics. 11 However, some key challenges for further advancement remain: the low mobility and stability of organic semiconductors, the lack of knowledge regarding structure property relationships for understanding the fundamental chemical aspects behind the structural design, and realization of desired properties. Organic field-effect transistors (OFETs) are a kind of device consisting of an organic semiconducting layer, a gate insulator layer, and three terminals (drain, source, and gate electrodes). OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but they also provide an important insight into the charge transport of πconjugated systems. Therefore, they act as strong tools for the exploration of the structure property relationships of πconjugated systems, such as parameters of field-effect mobility (μ, the drift velocity of carriers under unit electric field), current on/off ratio (the ratio of the maximum on-state current to the minimum off-state current), and threshold voltage (the minimum gate voltage that is required to turn on the transistor). 17 Since the discovery of OFETs in the 1980s, they have attracted much attention. Research onOFETs includes the discovery, design, and synthesis of π-conjugated systems for OFETs, device optimization, development of applications in radio frequency identification (RFID) tags, flexible displays, electronic papers, sensors, and so forth. It is beyond the scope of this review to cover all aspects of π-conjugated systems; hence, our focus will be on the performance analysis of π-conjugated systems in OFETs. This should make it possible to extract information regarding the fundamental merit of semiconducting π-conjugated materials and capture what is needed for newmaterials and what is the synthesis orientation of newπ-conjugated systems. In fact, for a new science with many practical applications, the field of organic electronics is progressing extremely rapidly. For example, using “organic field effect transistor” or “organic field effect transistors” as the query keywords to search the Web of Science citation database, it is possible to show the distribution of papers over recent years as shown in Figure 1A. It is very clear

Nanowire crystals of a rigid rod conjugated polymer.

In this paper, we show that well-defined, highly crystalline nanowires of a rigid rod conjugated polymer, a poly(para-phenylene ethynylene)s derivative with thioacetate end groups (TA-PPE), can be obtained by self-assembling from a dilute solution. Structural analyses demonstrate the nanowires with an orthorhombic crystal unit cell wherein the lattice parameters are a approximately = 13.63 A, b approximately = 7.62 A, and c approximately = 5.12 A; in the nanowires the backbones of TA-PPE chains are parallel to the nanowire long axis with their side chains standing on the substrate. The transport properties of the nanowires examined by organic field-effect transistors (OFETs) suggest the highest charge carrier mobility approaches 0.1 cm(2)/(V s) with an average value at approximately 10(-2) cm(2)/(V s), which is 3-4 orders higher than that of thin film transistors made by the same polymer, indicating the high performance of the one-dimensional polymer nanowire crystals. These results are particular intriguing and valuable for both examining the intrinsic properties of PPEs polymer semiconductors and advancing their potential applications in electronic devices.

Sulfonated Graphene for Persistent Aromatic Pollutant Management

Persistent aromatic pollutants are widely found in the effl uents from the pharmaceutical, petrochemical, dyestuff, pesticide, and other industries. Because of their high solubility in water, they transport into the environment widely and do harm to human health. Many studies have focused on the effi cient elimination of organic pollutants from aqueous solutions such as by photocatalysis, [ 1 ] adsorption, [ 2 ] and electrolysis. [ 3 ] Among these methods, adsorption techniques are simple and work effectively because of the preconcentration and solidifi cation of organic pollutants on adsorbents. However, the adsorption capacities of present materials are not high enough. It is important to develop new adsorbents with high adsorption capacities for persistent organic pollutant management in the environment. The high surface area of nanomaterials brings new prospects for the management of organic pollutants, for example, carbon nanotubes are found to work effectively to remove organic contaminants. [ 4 ] Compared with carbon nanotubes, graphene is more exciting. Graphene has a large theoretical specifi c surface area (2620 m 2 g − 1 ), [ 5 ] which indicates its potential for the adsorption of organic pollutants in environmental pollution management. However, to our knowledge, no report has addressed this topic, which is probably attributable to: 1) the strong aggregation of graphene sheets, which reduces the surface area of graphene signifi cantly, and 2) the absence of effective ways to disperse graphene in aqueous solution, which makes it diffi cult to advance in pollution management. Herein, we introduce a kind of sulfonated graphene (around 3 nm thick) with high dispersion properties in aqueous solution capable of absorbing naphthalene and 1-naphthol aromatic pollutants from aqueous solutions. The adsorption capability of the prepared sulfonated

25th Anniversary Article: Key Points for High‐Mobility Organic Field‐Effect Transistors

Remarkable progress has been made in developing high performance organic field-effect transistors (OFETs) and the mobility of OFETs has been approaching the values of polycrystalline silicon, meeting the requirements of various electronic applications from electronic papers to integrated circuits. In this review, the key points for development of high mobility OFETs are highlighted from aspects of molecular engineering, process engineering and interface engineering. The importance of other factors, such as impurities and testing conditions is also addressed. Finally, the current challenges in this field for practical applications of OFETs are further discussed.

High performance organic semiconductors for field-effect transistors

The purpose of this feature article is to give an overview of recent advances in development of high performance organic semiconductors for field-effect transistors, especially those with mobility of/over amorphous silicon, since they are believed to be promising candidates with practical applications in the near futures organic electronic industry. We hope this comprehensive summary of high performance organic semiconductors will provide guidelines for the design and synthesis of novel, high performance organic field-effect semiconductors.

Spherical α-Ni(OH)2 nanoarchitecture grown on graphene as advanced electrochemical pseudocapacitor materials

This work reports a new graphene-based composite for supercapacitor material, and the maximum specific capacitance of 1760.72 F g(-1) at a scan rate of 5 mV s(-1), with excellent cycling stability.

High Mobility, Air Stable, Organic Single Crystal Transistors of an n‐Type Diperylene Bisimide

Recently, some impressive progress has been made by functionalization of (hetero-)acenes, thiophenes, and arylenes with electron-defi cient constituents. [ 3–5 ] However, the development of air-stable, high mobility, n-type organic semiconductors for organic electronics is still highly emergent. The mobility of organic semiconductors depends on the effi ciency of charge transport from one molecule to another. Hence, some organic semiconductors with dense molecule packing always give high mobility. [ 6 ] As to the stability of organic compounds, it is believed that the highest occupied molecular orbital (HOMO) of p-type organic semiconductors should be more negative than –5.0 eV, e.g., locating at –5.0 to –6.0 eV, and the lowest unoccupied molecular orbitals (LUMO) of n-type organic semiconductors are best located between –4.0 and –4.5 eV, for anti-oxidation in air. [ 2 , 7 ] We have acknowledged these requirements and believe that perylene bisimides (PBIs) will fi t as candidates because of their reasonable electron acceptor ability, [ 8 ] and have been focusing on the expansion of the chemistry of perylene bisimides (PBIs) by a combination of Ullmann coupling and C–H transformation for some time, and have developed a facile strategy to synthesize fully conjugated, triply linked, diperylene bisimides, [ 8 ] conferring the expanded

Organic Single-Crystalline p−n Junction Nanoribbons

This article focuses on the growth and transport properties of organic single-crystalline p-n junction nanoribbons. The development of organic nanoelectronics requires the fabrication of organic nanometer-sized p-n junctions for high-performance devices and integrated circuits. Here we demonstrate the formation of single-crystalline p-n junction nanoribbons of organic semiconductors by selective crystallization of copper hexadecafluorophthalocyanine (F(16)CuPc, n-type) on copper phthalocyanine (CuPc, p-type) single-crystalline nanoribbons. The crystallization of F(16)CuPc onto CuPc requires several parameters, including similar molecular structures, similar lattice constants, and pi-stacking along the nanoribbon axis. Ambipolar transport of the p-n junction nanoribbons was observed in field-effect transistors with balanced carrier mobilities of 0.05 and 0.07 cm(2) V(-1) s(-1) for F(16)CuPc and CuPc, respectively. A basic p-n junction nanoribbon photovoltaic device showed current rectification under AM 1.5 simulated light. The discrete p-n junction nanoribbons may serve as ideal systems for understanding basic charge-transport and photovoltaic behaviors at organic-organic interfaces.

Synthesizing MnO2 nanosheets from graphene oxide templates for high performance pseudosupercapacitors

A facile method to synthesize layered manganese oxide nanosheets was developed for the first time by using graphene oxide as a template. The in situ replacement of carbon atoms on the graphene oxide framework by edge-shared [MnO6] octahedra provides a new methodology to synthesize graphene-based two-dimensional nanomaterials. The transformation of graphene oxide into δ-type MnO2 nanosheets results in an especially high surface area (157 m2 g−1), which is the highest value amongst todays MnO2 nanomaterials. Moreover, the MnO2 nanosheets demonstrated prominent capacitance (∼1017 F g−1 at a scan rate of 3 mV s−1, and ∼1183 F g−1 at a current density of 5 A g−1) and remarkable rate capability (∼244 F g−1 at a high scan rate of 50 mV s−1 and ∼559 F g−1 at a high current density of 25 A g−1), indicating their promise in high energy and power density pseudosupercapacitors.

Organic single crystal field-effect transistors: advances and perspectives

The perfect molecular order in organic crystals, the absence of grain boundaries and the minimized concentration of charge traps in crystals make them extremely promising for the study of intrinsic properties of organic materials and fabrication of high performance devices and circuits (e.g., high mobility) based on the organic crystals. Recently, enormous efforts have brought significant progresses in the development of new organic semiconductors for single crystals and the fabrication of high performance organic single crystal field-effect transistors (SCFETs). Here, the review will focus on organic semiconductors with high performance for single crystals, the techniques for the fabrication of organic SCFETs, the charge transport process in SCFETs, and the application of SCFETs for the development of novel SCFET arrays and complicate circuits. Finally, the perspectives and opportunities of SCFETs in near future is also addressed.