Electron and ambipolar transport in organic field-effect transistors.

Over the past 25 years, organic field-effect transistors (OFETs) have witnessed impressive improvements in materials performance by 3–4 orders of magnitude, and many of the key materials discoveries have been published in Advanced Materials. This includes some of the most recent demonstrations of organic field-effect transistors with performance that clearly exceeds that of benchmark amorphous silicon-based devices. In this article, state-of-the-art in OFETs are reviewed in light of requirements for demanding future applications, in particular active-matrix addressing for flexible organic light-emitting diode (OLED) displays. An overview is provided over both small molecule and conjugated polymer materials for which field-effect mobilities exceeding > 1 cm2 V–1 s–1 have been reported. Current understanding is also reviewed of their charge transport physics that allows reaching such unexpectedly high mobilities in these weakly van der Waals bonded and structurally comparatively disordered materials with a view towards understanding the potential for further improvement in performance in the future.

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25th anniversary article: organic field-effect transistors: the path beyond amorphous silicon.

Over the past 20 years, organic transistors have developed from a laboratory curiosity to a commercially viable technology. This critical review provides a short summary of several important aspects of organic transistors, including materials, microstructure, carrier transport, manufacturing, electrical properties, and performance limitations (200 references).

Organic thin-film transistors.

Creating functional electrical circuits using individual or ensemble molecules, often termed as “molecular-scale electronics”, not only meets the increasing technical demands of the miniaturization of traditional Si-based electronic devices, but also provides an ideal window of exploring the intrinsic properties of materials at the molecular level. This Review covers the major advances with the most general applicability and emphasizes new insights into the development of efficient platform methodologies for building reliable molecular electronic devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication. First, we summarize a number of different approaches of forming molecular-scale junctions and discuss various experimental techniques for examining these nanoscale circuits in details. We then give a full introduction of characterization techniques and theoretical simulations for molecular electronics. Third, we highlig...

Molecular-Scale Electronics: From Concept to Function

Polymers for flexible displays: From material selection to device applications

A surface treatment method has been developed for the SiO2∕Si substrate to control the electrical properties of pentacene thin-film transistors (TFTs). The surface treatment is performed by spin-coating 1,1,1,3,3,3-hexamethyldisilazane liquid, resulting in a drastic improvement of the off current although the surface treatment never shows a pronounced morphological change in the pentacene channel in comparison with the one on the nontreated substrate. The off current improvement directly enhances the transistor performance especially in the TFTs with a few monolayers channel thickness. The off current suppression could be caused by the reduction of the interfacial floating charge trapped at the pentacene∕SiO2 interface.

Modification of the electric conduction at the pentacene∕SiO2 interface by surface termination of SiO2

— Organic thin-film-transistor (OTFT) technologies have been developed to achieve a flexible backplane for driving full-color organic light-emitting diodes (OLEDs) with a resolution of 80 ppi. The full-color pixel structure can be attained by using a combination of top-emission OLEDs and fine-patterned OTFTs. The fine-patterned OTFTs are integrated by utilizing an organic semiconductor (OSC) separator, which is an insulating wall structure made of an organic insulator. Organic insulators are actively used for the OTFT integration, as well as for the separator, in order to enhance the mechanical flexibility of the OTFT backplane. By using these technologies, active-matrix OLED (AMOLED) displays can be driven by the developed OTFT backplane even when they are mechanically flexed.

A flexible full‐color AMOLED display driven by OTFTs

We established a dry-etching patterning process for the channel formation of pentacene thin-film transistor, and fabricated a four-terminal device equipped with a gate electrode. The four-terminal device enabled us to divide two-terminal source–drain resistance into two components of contact resistance and pentacene channel resistance. We obtained direct evidence of a gate-voltagedependent contact resistance change: the gate-induced charge significantly reduced the contact resistance and increased source–drain current. Furthermore, the temperature dependence of the device clearly indicated that the contact resistance was much higher than the channel resistance and was dominated in the two-terminal total resistance of the device below 120 K. An observed activation energy of 80 meV for contact resistance was higher than that of 42 meV for pentacene channel resistance.

Direct observation of contact and channel resistance in pentacene four-terminal thin-film transistor patterned by laser ablation method

— An 80-μm-thick rollable AMOLED display driven by an OTFT is reported. The display was developed so as to be rollable in one direction with an integrated OTFT gate driver circuit. It was successfully operated by an originally developed organic semiconductor, a peri-xanthenoxanthene derivative. The display retained its initial electrical properties and picture quality even after being subjected to 1000 cycles of a roll-up-and-release test with a radius of 4 mm.

An OTFT-driven rollable OLED display

We have developed an 80-μm-thick rollable AM-OLED display. The display is driven by an organic TFT backplane for which we have used originally developed semiconductor, a perixanthenoxanthene derivative. The display shows no degradation in a 4 mm-radius roll-up-and-release cycle of 1000 times.

Iwao Yagi

Papers

Modification of the electric conduction at the pentacene∕SiO2 interface by surface termination of SiO2

A flexible full‐color AMOLED display driven by OTFTs

Direct observation of contact and channel resistance in pentacene four-terminal thin-film transistor patterned by laser ablation method

An OTFT-driven rollable OLED display

47.3: A Rollable AM‐OLED Display Driven by OTFTs