Toray's New CNT-TFT Features World's Highest On/off Ratio

Aug 18, 2012
Tetsuo Nozawa, Nikkei Electronics

Toray Industries Inc formed a TFT (CNT-TFT) by using single-wall carbon nanotubes (CNTs) and a coating process and achieved a carrier mobility of 2.5cm2/Vs and an on/off ratio of 106.

The announcement was made Aug 17, 2012. The on/off ratio of 106 is one of the highest on/off ratios of CNT-TFTs in the world. The company plans to continue the development of the TFT in the aim of using it for displays.

CNT-TFTs are currently being developed by many research institutes and manufacturers. But many of the CNT-TFTs made by using a coating process have an on/off ratio of about 103. Some of the CNT-TFTs made by using a dry transfer method have a carrier mobility higher than 1,000cm2/Vs, but their on/off ratios are 105 or lower.

This time, Toray realized the high on/off ratio by using two technologies to increase the dispersibility of single-wall CNTs, which tend to cohere. First, the company developed its own P3HT (Poly(3-hexylthiophene)), which is a p-type organic semiconductor material used to disperse single-wall CNTs, by reexamining their molecular structure, etc. Because of its new structure, the P3HT tends to wind around single-wall CNTs.

Second, Toray newly developed a gate dielectric film material and optimized the dispersion state of the CNT thin film made by using the material. In addition, the new material enabled to reduce the high threshold voltage of the CNT-TFT to near zero.

Toray aims to use the new CNT-TFT as a TFT for displays and form it with an ink-jet method. The details of the CNT-TFT will be announced at the JSAP-OSA Joint Symposia for 2012 JSAP Autumn Meeting, which will take place from Sept 11 to 14, 2012, at Ehime University in Japan.