Sunday, 22 Sep 2019

Researchers develop organic circuits using novel coating technique

The research group created D-type flip-flop registers, these were used to form memory, and used to form 4-bit shift registers that help serialise the data to be transmitted

27 Jan 2015 | Editor

According to an article on the Tech-On news website Japanese research from, University of Tokyo and the Technology Research Institute of Osaka Prefecture, formed an all organic semiconductor CMOS circuit and temperature sensor using printing deposition process, that was connected to an antenna used to transmitted temperature data at 13.56MHz.

These latest results were realised by using a single crystal organic semiconductor that had a charge carrier mobility of 16.2 cm2V-1s-1, more than 10 times higher than a "conventional" organic material. The researchers believe that because the circuits were printed and no vacuum deposition is required then it should be possible to reduce manufacturing cost by more than 90% compared to more traditional "vacuum"deposition manufacturing.

University of Tokyo - Organic

Figure: University of Tokyo - Organic "CMOS" type circuit

To fabricate the CMOS type circuit the researchers developed novel coating technique which they call "coating crystallisation method." This technique can be used with either n-type or p-type single crystal organic semiconductor material that is mixed with a high viscosity polymer to form a mixed solution, which is then deposited on to a substrate. When the solution is drying, polymer and single crystal organic material layers are formed on the lower and upper sides, respectively. Alternating lines of p-type and n-type lines are drawn with a space in between, electrodes drawn on a separate layer and connected to form individual organic semiconductor devices.

The research group created D-type flip-flop registers, these were used to form memory, and used to form 4-bit shift registers that help serialise the data to be transmitted.

A simple temperature sensor was created by taking advantage of the fact that the resistance value of the "PEDOT:PSS" - a conducting polymer - is dependant on temperature. In addition, the researchers also fabricated a circuit that converts analogue resistance data in to digital data ready for transmission. The researchers also fabricated a rectifier circuit using organic TFT elements again made using the "coating crystallisation method".

The research group has achieve many important developments:

  • a high-performance organic TFT using a single crystal organic material in 2011
  • drove an LCD display using the coating crystallization method in 2012
  • developed a low-cost RFID tag rectifier based on a single crystal TFT in 2014

The researchers already have their eyes set on future developments including plans to develop an RFID tag equipped with a temperature sensor for logistics management, which the group are expecting to commercialise.

At the "High-end Organic Semiconductor R&D/Education Centre" researchers conduct joint research with companies that develop organic semiconductor materials, panel components, devices, and related technology for the development of organic electronics devices that operate at high speeds for a wide variety of applications.

techon.nikkeibp.co.jp/english/    www.u-tokyo.ac.jp/en/    www.osakafu-u.ac.jp   

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