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Printed Electronics World
Posted on March 30, 2010 by  & 

Transistors on plastic

Organized by the PPE-KTN
Last week, the Photonics and Plastic Electronics KTN put together a one day seminar that gave an overview of the activity in the UK on the topic of flexible organic and inorganic transistors.
Speakers were representing both Universities around the country as well as companies that are developing transistor/backplane technologies. Inorganic, organic and hybrid versions are being developed in order to evaluate the performance of each type of device.
Stephen Yeates described the small molecule/polymer blend of materials researched at Manchester University, combining the high mobility of small molecules such as TIPS-Pentacene and the controlled structure achieved using polymers, the target being a highly amorphous polyacene.
The introduction of polymers would also affect the rheological properties during inkjet printing, due to the influence of polymeric elongational flow on viscosity. Different solvents are also tested in order to monitor their influence on crystallization and mobility.
PETEC is also researching organic TFTS, with mobilities achieved of about 0.9 cm.sq/v.s with a 7% variation that's probably adequate for driving e-paper but not uniform enough to be used for OLED driving. Highest processing temperature seen by these materials is still very low though, at about 110 degrees celsius. The first demonstrator would be available around June with a 3in active matrix electrophoretic display using E Ink's technology.
Andrew Flewitt from Cambridge University focused on inorganic transistors based on metal oxides, which are aiming to displace a-Si in terms of performance. The added benefit of transparency of these devices would lead to new applications that researchers in Cambridge are very excited about, given the impact on new product design that transparent TFTS, sensors, RFID and solar cells would have.
The higher mobility observed in metal oxide transistors is attributed to the s-shell dominated electron conduction which, even in amorphous structures, ensures adequate overlap that does not impede electron flow. InZnO transistors (In: 10%, Zn: 90%) are a good example of a very good amorphous structure achieved. The team is also researching CuO (an n-type semiconductor) and Cu2O (a p-type semiconductor) that can both be deposited, paving the way towards CMOS manufacturing.
Thomas Anthopoulos on the other hand presented work at Imperial College that is focusing on hybrid organic/inorganic transistors: p-type small molecule/polymer blends and ZnO n-type transistors all processed at very low temperatures.
Richard Price of Nano ePrint described the company's collaboration with Novalia for the design of innovative greetings card for Tiger Print, a company of Hallmark. The company is aiming to have 10,000 greeting cards available by this time next year 2011, incorporating the design that is currently under development. Other applications Nano ePrint is targeting include brand protection labels, card games, fabric-embedded electronics, etc.
Finally Patrick Too of Plastic Logic described the company's QUE™ e-reader device, with organic TFTs manufactured via photolithography/wet etching and incorporating some printing steps too, all processes being conducted at low temperatures. Patrick inferred that the company's next products that are currently under development are not necessarily going to be e-paper displays. Instead, Plastic Logic is looking into utilizing very different display technologies for those.
The event also included a presentation from Mathew Ball who outlined the EPSRC Electronics Strategy and funding opportunities for the electronics sector which, for this year are approximately 26% of the £3.1 billion that is divided among all UK Research Councils.

Authored By:

Principal Analyst

Posted on: March 30, 2010

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