Campinas, Brazil, November 20, 2008 — On Tuesday Norbert Fruehauf, Chair of Display Technology at the University of Stuttgart, presented the work done in his group on using carbon nanotubes (CNTs) as a semiconductor material for TFTs in liquid-crystal displays, as well as for transparent conductors to replace ITO. Fruehauf was speaking at LatinDisplay 2008, which concluded here yesterday.

Ken Werner
Senior Analyst and Editor

It seems that when you fabricate single-wall CNTs (SWCNTs), one third of the possible structures are conducting and two thirds are semiconducting. At low densities there is a regime where a closed network is formed only by the semiconducting SWCNTs. The semiconducting components are needed for TFTs whereas the conducting parts are needed to replace ITO.

Typical TFT devices have semiconductor on/off ratios of up to 105 and carrier mobilities of 1 cm2/Vs. If there were a practical separation method for increasing the percentage of semiconducting SWCNTs, much higher mobilities could be obtained — but complete separation isn’t required. Said Fruehauf: "I regard CNTs as the next generation of organic TFT materials."

Fruehauf also described a novel (and patented) three-TFT pixel switch for AMOLEDs. The circuit features a separate current-sensing line that provides error-correcting feedback during the voltage-addressing period. The TFTs were fabricated with a self-aligned p-channel LTPS process.

Bernard Coll, the head of Motorola’s new 3D research program, provided an overview of 3D display options for mobile displays and provided some insights into Motorola’s thinking about 3D. Coll feels the best target platforms for 3D will feature 3.5 to 8-inch screen sizes, and favor lenticular and time-sequential 3D approaches. The first practical commercial mobile applications (as opposed to short-lived and faddish) will involve gaming, user interfaces, and mapping.

Among many other presentations, there was significant coverage of solar cell opportunities from Gopalan Rajeswaran of Moser Baer (formerly of Kodak’s OLED program) and Corning’s Anis Fadul. Corning is developing glasses specifically for solar cell applications and finding significant interest from potential customers, Fadul said.

The Brazilian government, through the Brazilian Development Bank, is supporting the development of a display industry in Brazil. Margarida Baptista, Special Advisor to the bank’s president, described the multi-faceted program, which contains tools for all levels of investment and development of production capacity. Tools are available to support large projects, including equity sharing. How large? When I asked Baptista if the equivalent of US$3B for an advanced-generation fab would be consistent with the program, she said that would depend entirely on the overall proposal. Non-Brazilian companies qualify for the program if production facilities are being constructed in Brazil.

Baptista went on to say that the bank is the main provider of long-term financing in Brazil, with US$42B in disbursements in 2008, up from US$11B in 2003. That’s a larger budget than the World Bank and the Inter-American Development Bank together, she said.

A roundtable discussion — which, in the interest of full disclosure, I should say I coordinated — attempted to identify initial practical projects for a Brazilian display industry. Among the recommendations were passive OLED displays, where the intention would be to start small and scale to larger substrates later. In addition, active-matrix displays; back-end assembly of TVs, monitors, and modules; and perhaps the purchase of a Gen 6 LCD fab, should be considered too. These recommendations were made in the context of what Baptista called "a trade deficit in displays."

"Our goal," said Baptista, "is to start up FPD production in emerging technologies here." LatinDisplay 2008 supported that goal by bringing Brazilian players together with noted members of the international display community.