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

Semiconducting π-conjugated systems in field-effect transistors: a material odyssey of organic electronics.

About Supramolecular Assemblies of π-Conjugated Systems

Electron and ambipolar transport in organic field-effect transistors.

Organic semiconducting oligomers for use in thin film transistors.

Field-effect transistors based on solution-processible organic semiconductors have experienced impressive improvements in both performance and reliability in recent years, and printing-based manufacturing processes for integrated transistor circuits are being developed to realize low-cost, large-area electronic products on flexible substrates. This article reviews the materials, charge-transport, and device physics of solution-processed organic field-effect transistors, focusing in particular on the physics of the active semiconductor/dielectric interface. Issues such as the relationship between microstructure and charge transport, the critical role of the gate dielectric, the influence of polaronic relaxation and disorder effects on charge transport, charge-injection mechanisms, and the current understanding of mechanisms for charge trapping are reviewed. Many interesting questions on how the molecular and electronic structures and the presence of defects at organic/organic heterointerfaces influence the device performance and stability remain to be explored.

Device Physics of Solution‐Processed Organic Field‐Effect Transistors

Ultrathin films of regioregular poly(3-hexyl thiophene) (RR-P3HT) were deposited through a dip-coating technique and utilized as the semiconducting film in field-effect transistors (FETs). Proper s...

Ultrathin Regioregular Poly(3-hexyl thiophene) Field-Effect Transistors

High-Performance All-Polymer Transistor Utilizing a Hygroscopic Insulator

Utilizing roll-to-roll techniques for manufacturing source-drain electrodes for all-polymer transistors

Despite the great promise of printed flexible electronics from2D crystals, and especially graphene, few scalable applica-tions have been reported so far that can be termed roll-to-rollcompatible. Here we combine screen printed graphene withphotonic annealing to realize radio-frequency identificationdevices with a reading range of up to 4 meters. Most notablyour approach leads to fatigue resistant devices showing lessthan 1% deterioration of electrical properties after 1000 bend-ing cycles. The bending fatigue resistance demonstrated on avariety of technologically relevant plastic and paper sub-strates renders the material highly suitable for various print-able wearable devices, where repeatable dynamic bendingstress is expected during usage. All applied printing and post-processing methods are compatible with roll-to-roll manufac-turing and temperature sensitive flexible substrates providinga platform for the scalable manufacturing of mechanicallystable and environmentally friendly graphene printed electronics.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pssr.201600330

Graphene screen-printed radio-frequency identification devices on flexible substrates

We have fabricated solution processable polymer transistors with high conductivity, requiring only a few volts for obtaining good current modulation. The devices can be fabricated and operated in air and the operation is greatly enhanced in humid atmosphere. Devices reach an On∕Off ratio of about 600 and a subthreshold swing of 500mV per decade operating on voltages less than 2V. In this letter the mechanism behind the current modulation is investigated, and we show that the current is modulated through ion-assisted oxidation and reduction of the semiconductor by ions moving vertically in the insulator material to the transistor channel.

Henrik G.O. Sandberg

Papers

Ultrathin Regioregular Poly(3-hexyl thiophene) Field-Effect Transistors

High-Performance All-Polymer Transistor Utilizing a Hygroscopic Insulator

Utilizing roll-to-roll techniques for manufacturing source-drain electrodes for all-polymer transistors

Graphene screen-printed radio-frequency identification devices on flexible substrates

Current modulation of a hygroscopic insulator organic field-effect transistor