A Japanese research group formed an electronic circuit including organic transistors on a very thin resin sheet by using only printing technology.
The group is led by Shizuo Tokito, professor at Yamagata University and vice director of Research Center for Organic Electronics (ROEL). A thesis about the new technology was published on the Nature Communications magazine.
The electronic circuit was formed on a 1μm-thick resin film called "Parylene-C." The thickness of the entire circuit is 2μm or less. And its weight per unit area is 2g per 1m2, which is almost ignorable.
The carrier mobility of the organic TFT in the saturation region is up to 1.0cm2/Vs, and the current on/off ratio is 106, which is equivalent to that of a TFT using amorphous silicon (Si). Even when the circuit was bent to a very acute angle (a curvature radius of 140μm), the on-state current and carrier mobility changed only by 1.6% and 3.9%, respectively. The on/off ratio was 105 or higher.
The research group expects that the circuit will be employed for sensors that are attached to human body and used for healthcare purposes. It can be attached to complex curved surfaces such as of the neck and elbow and bent and stretched.
When an array of 400 organic TFTs was formed on a resin sheet measuring 10 x 10cm with the new technology and 1/4 of the TFTs were randomly selected for evaluation, most of their carrier mobilities were within the range of 0.34±0.15cm2/Vs.
At SID 2014, an international conference on display technologies, which took place in June 2014, Tokito announced that he had formed an array of 10 x 10 organic TFTs on a 32.5 x 32.5mm PEN sheet with a thickness of 125μm. At that time, the carrier mobilities of the TFTs were within the range of 1.1±0.17cm2/Vs.