A team headed by Dr. Kazuhito Tsukagoshi, a Principal Investigator at the International Center for Materials Nanoarchitectonics (MANA; Director-General: Masakazu Aono), National Institute for Materials Science (President: Sukekatsu Ushioda), in joint research with Professor Kazuo Takimiya of Hiroshima University, succeeded in fabricating an organic transistor with the world¡¯s highest field effect mobility directly on a substrate by developing a solution process for producing organic crystal transistor from solution.
With the development of mobile devices such as notebook PCs and electronic books, portability of information/image media is progressing. However, liquid crystal displays, which are currently the mainstream technology, are produced on a glass substrate due to limitations on the transistor manufacturing temperature. Although thinner glass substrates are required in order to reduce weight and thereby improve portability, there are limits to glass thickness, as glass substrate displays have low impact resistance and are easily broken. To solve this problem, if organic transistors can be used, it will be possible to manufacture high performance pixel-drive transistor arrays on plastic substrates, which offer the combined advantages of light weight and flexibility.
In this work, the researchers independently developed a method that makes the fullest possible use of self-assembly, in which crystals are formed by spontaneous overlaying of organic molecules. High performance organic crystal transistors can be produced simply by spin-coating the material, which is dissolved in an organic solvent, on a substrate, and then exposing the material to a solvent vapor for several hours. Normally, organic thin film devices contain a large number of crystal grain boundaries, which reduce conductivity. However, this crystal film contains no grain boundaries, and high characteristics can be obtained even when the film is fabricated in air. A transistor which was fabricated using this crystal achieved the world¡¯s highest field effect mobility of 9.1cm2/Vs in a transistor produced from a solution. This is a dramatic improvement in comparison with the field effect mobility of many devices produced by general solution methods, which is limited to approximately 1cm2/Vs.
With conventional organic semiconductor single crystals, where electrical conductivity is concerned, mobility increases when the device is cooled, reaching at peak at around -70¡ãC, and then decreases at lower temperatures. However, with the device produced by this method, mobility increased continuously in measurements down to -200¡ãC, and there was no scattering of electrical conductivity due to crystal grain boundaries, etc. Although the mechanism of conduction in organic crystal semiconductors had been disputed until now, this result also clarified the fact that the mechanism responsible for conduction is band-type conduction.
This method is simple and does not require a vacuum device, etc., and it easily improves the properties of organic semiconductors. In the future, application to roll-type continuous processes will also be possible, and it will be effective in research aimed at realizing flexible information/image media.
This research was carried out as part of the research topic ¡°High Operating Speed Organic Transistors by Nano Interface/Electronic State Control¡± (Research Representative: Kazuhito Tsukagoshi) in the research field ¡°Establishment of Innovative Manufacturing Technology based on Nanoscience¡± (Research Supervisor: Yasuhiro Horiike, Emeritus Fellow, National Institute for Materials Science) in the Japan Science and Technology Agency Targeted Basic Research Program ¨C Team Type Research (Core Research for Evolutional Science and Technology: CREST).
For more detail:Kazuhito Tsukagoshi
Physics, photosynthesis and solar cells
01.12.2016 | University of California - Riverside
New process produces hydrogen at much lower temperature
01.12.2016 | Waseda University
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy