Under the NEDO project, a group consisting of The University of Tokyo and others successfully transmitted an unique identification signal at a commercial frequency using high performance organic thin film transistor that can be manufactured by print process.
Based on the technology that coat and crystalize organic semiconductor, the group developed an organic TFT rectifying device and successfully transmitted unique identification by radio frequency at a commercial band of 13.56MHz. The performance is 10 times higher than the conventional coat type organic semiconductor at less than 1/10 the cost. The result verifies that it can be used as an actual device via integrated process of the print process.
Organic semiconductors, compared with the current inorganic semiconductors such as silicon, have the following features. Active application developments are being conducted for electronic devices such as the next generation transistor.
(1) Simple method such as coating and printing and easy production by relatively low temperature.
(2) Thin form
(3) Low cost
(4) Unique application such as plastic RFID and flexible display.
Previously, it was difficult to obtain a high speed response performance from a RFID tag when communicating at commercial frequency band. The NEDO project will promote the development of innovative plastic RFID using organic semiconductor by forming a joint industry-academic team consisting of research institutes that develop the core technology and companies belonging to different industries.
1. World's First Contactless RFID Communication by Low Cost Printed Device
Technology developments indicated below allow the creation of high performance organic TFT rectifying device that is proven to respond to a commercial frequency of 13.56MHz using print process.
(1) High Mobility and Thermostable Organic Semiconductor "Alkyl DNBDT"
The group of JNC Corporation, Tokyo University, and Rigaku Corporation developed an organic semiconductor "Alkyl DNBDT" that has 10cm2/Vs carrier mobility that is more than ten times faster than the conventional coated organic transistor performance which is 0.1-1cm2/Vs. The mobility is extremely high value and is essential for organic TFT to respond to high frequency. Moreover, since the material is stable even under the temperature of 150 degrees, it is highly advantageous over the others as an application material for device production process.
(2) New Coat/Print Process "Coat Crystallization"
"Coat Crystallization" developed by Tokyo University group, is an easy method to crystallize while coating the organic semiconductor solution to form a film. In the newly developed method, an "Organic Mono-Crystal Wafer" with the size of 10cm square can be created. (Diagram 2) The organic semiconductor molecule align orderly allowing organic semiconductor with high mobility to be formed, which is suitable for creating large volume of transistors with the same property.
(3) Development of Organic Semiconductor Device Integration Process
Technology Institute of Osaka Prefecture and Tokyo University developed a method to create a high performance organic TFT using lithography patterning method that does not damage the organic semiconductor. By this method, the institute developed a rectifying device for RFID communication with two combined transistors.
(4) RFID Communication Achieved by Connecting High Response Organic TFT Rectifying Device to Low Cost Antenna.
By directly connecting the rectifying device with low cost antenna developed by Toppan Forms, the group was able to transmit a 13.56MHz RFID signal. Moreover, using oscillation circuit of a different frequency verified the unique identifying function.
The group's achievement of establishing the base property of RFID communication by printable organic rectifying circuit will lead to the development of a RFID tag. The research development effort verifies that an organic TFT with 10 times the performance can be printed at 1/10 the cost and via the integration process it can be used as an actual device. Currently the group is moving forward to create a logic circuit module on RFID tag to enable unique identification of higher volume using the same method. Since devices can be coated or printed at once on a large film surface allowing low cost production, it will lead to the popularization of energy saving electronic tag for logistic efficiency improvement and sensing device.
2. Technical Background
Professor Takeya et al. in 2003 developed the crystallized organic semiconductor and discovered that significantly higher performance can be achieved compared to the conventional technology. They continued their effort to find the better practical liquid coating method to create an organic semiconductor. In 2011, a significantly high performing organic TFT was developed by extracting organic semiconductor crystal from a solution. In 2012, they succeeded in driving the LCD using the coat crystallization method. This time, by using the high-speed response property of the mono-crystal TFT, it was proven that the technology can be used for low cost RFID tag.
Under the NEDO project, the group will accelerate the research and development by creating a RFID prototype with logic circuit (Diagram 4) for practical use. Moreover, the consortium "High End Organic Semiconductor Research, Development & Training Center" formed within Tokyo University that work with private companies to develop organic material, panel material, equipment and device will not limit themselves to RFID tags but also develop a wide range of high performance organic electronic devices.
Source and top image: Toppan Forms
For more attend : Printed Electronics USA November 19-20 2014 Santa Clara, USA