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Nano ink printed transistor breakthrough brings us closer to flexible organic TFTs

MANA has had a breakthrough with its nano ink technology for printed electronics, which will enable production of printable organic TFTs suitable for flexible displays.
July 16, 2014
flexible display concept

When it comes to mobile devices, display technology is one area that has managed to continually offer up noticeable improvements and changes over the past few years, be it tweaks to image quality, pixel resolution/density, and even the shape and curvature of the display.

In Japan, the International Center for Materials Nanoarchitectonics (or MANA for short) has announced another step forward for display technology, in the form on a new Nano Ink that can be used in the printing of flexible organic thin film transistors (OTFT) at room temperature. TFTs are an essential technology used in display backplanes, and are responsible for controlling the light parts, be that LCD or OLED, of the visible display.

Display Panel Transistors
Thin film transistors are used to turn colored pixels on and off in OLED displays.

Although printed circuitry has been in development in various forms for a little while, MANA claims to have developed a new technique which overcomes the high temperature annealing processes typically associated with printed electronics. This means that its technique can be used to print more complex components onto plastic substrates, which is perfect for flexible electronics and display products.

If you are interested in how MANA’s technology works, it uses a new nanoparticle, although they haven’t said exactly what it is, which is surrounded by “planar aromatic molecules”, which is what allows for the transfer of electrical charge. This is different from other non-conductive materials that are used to surround other inks, which have to be removed using high temperature annealing before any components would work. It is this high temperature that destroys the plastics that would be required to create flexible displays. This breakthrough opens the door not only for simplified production of flexible electronics, but should also eventually result in cheaper manufacturing costs.

Nano Ink printed OTFT
MANA has demonstrated nano ink OTFTs printed on plastic and paper sheets.

Importantly for display panels, the MANA group’s OTFTs offer up high electron mobility, which is essential for powering higher current AMOLED lights, the technology currently leading the field of flexible displays. These OTFTs should be able to handily outperform amorphous silicon (aSi) based TFTs, which is typically used in cheaper lower resolution displays, and has sufficient electron mobility to compete with IGZO, which is able to offer many of the benefits of high quality LTPS backplanes found in expensive high resolution panels.

MANA researchers have already tested out its OTFT designs on a flexible plastic polymer and a paper substrate, resulting in a mobility of 7.9 and 2.5 cm2/ V-sec respectively. For comparison, IGZO tend to start with a mobility of around 10 cm2/ V-sec and upwards, whilst aSi has a typical mobility around 1 cm2/ V-sec. Sharp boasts that its IGZO technology is capable of 20 cm2/ V-sec.

As with all new technological breakthroughs, there is still more testing and prototyping to be done before this ends up anywhere near a final product. Even so, printable flexible electronics are an important technological step towards the future of truly flexible devices, that we will certainly be keeping an eye on.