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.

Recent Advances in Bulk Heterojunction Polymer Solar Cells

The optoelectronic properties of polymeric semiconductor materials can be utilized for the fabrication of organic electronic and photonic devices. When key structural requirements are met, these materials exhibit unique properties such as solution processability, large charge transporting capabilities, and/or broad optical absorption. In this review recent developments in the area of π-conjugated polymeric semiconductors for organic thin-film (or field-effect) transistors (OTFTs or OFETs) and bulk-heterojunction photovoltaic (or solar) cell (BHJ-OPV or OSC) applications are summarized and analyzed.

π-Conjugated Polymers for Organic Electronics and Photovoltaic Cell Applications†

In this Progress Report we provide an update on recent developments in inkjet printing technology and its applications, which include organic thin-film transistors, light-emitting diodes, solar cells, conductive structures, memory devices, sensors, and biological/pharmaceutical tasks. Various classes of materials and device types are in turn examined and an opinion is offered about the nature of the progress that has been achieved.

Inkjet Printing—Process and Its Applications

Organic semiconducting oligomers for use in thin film transistors.

This report examines the influence of narrow band gap polymer end groups (bromine or thiophene) on the performance of field-effect transistors prepared using these polymers. The conjugated polymer chains that were capped with thiophene units enhanced the intermolecular packing structure and decreased device hysteresis by removing charge traps. The presence of the end-capping groups increased the hole mobility by a factor of 2 or 4, depending on the molecular weight of the polymer, in the bottom contact field-effect transistors.

Charge transport behaviors of end-capped narrow band gap polymers in bottom-contact organic field-effect transistors

Post surface treatment of LiNi0.6Co0.1Mn0.3O2 electrode with poly(4-vinylphenol) for lithium ion batteries

Enhanced ionic conductivity of the solid electrolyte for lithium-ion batteries

With the aim of improving the electrical and adhesion properties of the indium–tin–oxide (ITO) electrode/organic interface, we tested Cl- and CF3-terminated self-assembled monolayers (SAMs), which react with the indium atoms of the electrode, and compared the results to those obtained using a CH3-terminated SAM. The contact resistance of the interface between the Cl-terminated surface and the ITO electrode (1.5kΩ) was found to be much lower than that of the interface between the ITO and the CF3-terminated surface (21.3kΩ), which can be attributed to the higher dipole moment of the In–Cl complex compared to the In–F complex. In the ITO films deposited on the CH3-terminated surface, the contact resistance (138.0kΩ) was much higher than those of the reactive metal contacts because the ITO thin film deposited on the CH3-terminated surface does not react with the SAM.

Reactive metal contact at indium–tin–oxide/self-assembled monolayer interfaces

The present invention provides ink- jet printing ink for organic semiconductors, and, more particularly, provides ink- jet printing ink for organic semiconductors, which can be used to form a uniform crystalline thin film. The ink- jet printing ink of the present invention includes a mixed solvent composed of a first solvent and a second solvent having a higher boiling point and lower surface tension than the first solvent, thus forming a uniform crystalline thin film in a volatilization process. Further, the present invention provides a circular organic thin film transistor having a high field-effect mobility of about 0.12 cm 2 V 1 S -1 .

Yeong Don Park

Papers

Charge transport behaviors of end-capped narrow band gap polymers in bottom-contact organic field-effect transistors

Post surface treatment of LiNi0.6Co0.1Mn0.3O2 electrode with poly(4-vinylphenol) for lithium ion batteries

Enhanced ionic conductivity of the solid electrolyte for lithium-ion batteries

Reactive metal contact at indium–tin–oxide/self-assembled monolayer interfaces

Ink-jet print ink and organic thin film transistor using thereof