Junshi Soeda

Patternable Solution‐Crystallized Organic Transistors with High Charge Carrier Mobility

Development of high-performance printed semiconductor devices is highly desired with the expectation for the nextgeneration technologies of “printable electronics” providing simply fabricated, fl exible, large-area, low-cost, and environmentally friendly electronic products such as paper-like fl exible displays. Patterned arrays of printed organic fi eld-effect transistors (OFETs) based on chemically stable solutionprocessed organic semiconductors are regarded as key devices that operate as fundamental switching components in, for example, pixel-controlling active-matrix elements. However, performance of conventional solution-coated noncrystal organic thin-fi lm transistors has yet to be improved for practical use in general electronic circuitry. Here, newly developed arrays of patterned crystalline OFETs of air-stable compound 2,9-didecyl-dinaphtho[2,3-b:2’,3’-f ]thieno[3,2-b]thiophene (C 10 -DNTT) formed from hot solution are presented. A method of oriented growth is introduced to provide the singlecrystalline fi lms of C 10 -DNTT that regulates the crystallizing direction and positions in a single process. The benchmark value, 10 cm 2 V − 1 s − 1 , of the charge mobility is achieved for the present OFETs, far exceeding the performance of former devices and opening a practical way to realize printed and fl exible electronics with suffi cient switching speed. The result is attributed to almost perfect molecular periodicity in the crystal fi lms, which allows effective intermolecular charge transport of the electrons.

Solution-crystallized organic field-effect transistors with charge-acceptor layers: high-mobility and low-threshold-voltage operation in air.

For the development of low-cost fl exible electronic devices organic fi eld-effect transistors (OFETs) are highly anticipated for use in fundamental switching components because OFETs allow easy production routes from solution at low temperatures, which do not damage the plastic substrates. Processes such as the spin-coating of polymers or polycrystalline thin fi lms are indeed very advantageous because they allow mass production on large-area plastic backplanes. However, the typical performance of solution-coated organic thin-fi lm transistors is not yet satisfactory for their expected use in common applications such as active matrices in large-area fl exible displays. Though mobility of more than 10 cm 2 V − 1 s − 1 is achieved for devices based on vapor-grown organic single crystals, [ 1–3 ] these “hand-made” devices are not suitable for industrial production. In addition, an equally important requirement for their practical usage is stable operation in ambient atmosphere. Here, we report high-mobility organic single-crystal transistors of air-stable compound 2,7-dioctyl[1]benzothieno[3,2b ][1]benzothiophene (C 8 -BTBT) treated with a 2,3,5,6-tetrafl uoro-7,7,8,8tetracyanoquinodimethane (F 4 -TCNQ) solution. A method of oriented growth is employed to provide fully single-crystal domains of the C 8 -BTBT main channels, regulating crystallographic direction during the fi lm growth. Charge mobility as high as 3.5–6 cm 2 V − 1 s − 1 is achieved in the saturation regime, owing to the almost perfectly periodic crystal packing that allows effective intermolecular exchange of π electrons. Excellent air stability due to the high ionization potential is reported for C 8 -BTBT, [ 4 ] though it had the drawback of a relatively high

High Electron Mobility in Air for N,N′‐1H,1H‐Perfluorobutyldicyanoperylene Carboxydi‐imide Solution‐Crystallized Thin‐Film Transistors on Hydrophobic Surfaces

After remarkable progress in developing organic semiconductors during the last decade, it remains challenging to achieve highmobility, air-stable and solution-processed organic fi eld-effect transistors (OFETs) based on electron-transporting (n-type) materials with a performance comparable to that of hole-transporting (p-type) organic semiconductors. [ 1 ] Both types of semiconductor are needed for industrial applications based on high-speed complementary logic devices. As seen for complementary metaloxide-semiconductor (CMOS) devices in current silicon technology, high-performance, organic complementary circuits will enable the development of low-cost and large-area electronic devices, even on plastic substrates via simple printing processes. For this purpose, it is necessary to develop high-performance devices processed at near room temperature from solution. Since the performance of solution-processed p-type organic semiconductors has advanced recently, it is now needed to improve the performance of the corresponding n-type OFETs. Although the highest mobility for molecular semiconductors that has been reported for solution-crystallized p-type OFETs is > 10 cm 2 V − 1 s − 1 , [ 2a ] the maximum value reported for n-type devices is only 0.16 cm 2 V − 1 s − 1 . [ 2b ] We have developed a technique to form highly crystalline, n-type, organic semiconductor fi lms on low-surface-energy gate dielectrics so that a carrier mobility > 1 cm 2 V − 1 s − 1 is achieved for an important material, N , N′ -1 H ,1 H -perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN 2 ), when processed in ambient atmosphere.

Doping of organic semiconductors : Impact of dopant strength and electronic coupling

Molecular doping: The standard model for molecular p-doping of organic semiconductors (OSCs) assumes integer charge transfer between OSC and dopant. This is in contrast to an alternative model based on intermolecular complex formation instead. By systematically varying the acceptor strength it was possible to discriminate the two models. The latter is clearly favored, suggesting strategies for the chemical design of more efficient molecular dopants.

High-Speed Flexible Organic Field-Effect Transistors with a 3D Structure

Organic semiconductor materials offer fl exible platforms for charge current due to their weak van der Waals interaction between π -conjugated organic molecules such that the transport of electrons or holes is activated with modest mobility. Making use of such material properties, technologies of fl exible organic fi eld-effect transistors (OFETs) are in the process of developing attractive devices with fl exible, stretchable, light-weight, low-cost, and low-power-consumption switching components, such as active-matrix elements for plastic displays, [ 1–4 ] sensor arrays, [ 5 , 6 ]

Novel Solution Process for Inch-Sized Single-Crystalline Organic Semiconductors and Application for Arrayed TFTs

A method of continuously growing large-domain organic semiconductor crystals is developed to fabricate multiple arrayed high-mobility organic transistors. Solution of an organic semiconductor is held at the edge of a moving blade in order to grow large area crystalline thin film. As the result of continuous evaporation of the solvent at an elevated temperature around 100 °C with the supply of the solution in the same rate, the organic crystals steadily grow on the substrate to the size of inches. Arrays of field-effect transistors exhibit high performances with the mobility up to 10 cm 2 /Vs based on the large-domain crystal films.

CCDC 886147: Experimental Crystal Structure Determination

Related Article: Toshihiro Okamoto,Chikahiko Mitsui,Masakazu Yamagishi,Katsumasa Nakahara,Junshi Soeda,Yuri Hirose,Kazumoto Miwa,Hiroyasu Sato,Akihito Yamano,Takeshi Matsushita,Takafumi Uemura,Jun Takeya|2013|Adv.Mater.|25|6392|doi:10.1002/adma.201302086