OTFT - Page 5

UK's SmartKem announced that they signed a joint-development agreement with a major Asian display OEM. Under the agreement, SmartKem and the display maker will customize Smartkem's p-FLEX organic semiconductor inks for solution-based flexible TFT backplane technology.

SmartKem will formulate, transfer and supply p-FLEX materials to the display maker which will enable production of high-performance TFTs onto plastic substrates through low-temperature processing.

During the FPD International 2013, SEL unveiled a new 13.5" QFHD (3840x1260, 326 PPI) flexible OLED prototype. This is a WRGB panel (white OLEDs with color filters) and it uses a CAAS-OS (C-Axis Aligned Crystalline Oxide Semiconductor) substrate.

Toshiba was also showing a flexible panel - a 10.2" WUXGA (1920x1200, 223 PPI) WOLED panel on an IGZO backplane. This seems to be the same panel shown at SID 2013 in May 2013. Finally, Yamaga University's Research Center for Organic Electronics (ROEL) unveiled new flexible OLED technologies, including soluble organic-TFT based panels (on PET).

Researchers from the University of Tokyo developed a highly-flexible OLED lighting device that can work even after being completely bent and crumpled. They hope that this device can be used for medical and healthcare sensors.

The flexible panel uses a metal electrode (LiF/Al), a transparent PEDOT:PSS transparent electrode and a polymer substrate. The minimum bending radius is 10 micrometer and the brightness of the panel is 100 cd/m².

Plastic Logic developed a new OTFT-based flexible 42" e-paper (E Ink) display, made from 16 10.7" flexible panels tiled together. This display is thin (less then 3 mm) and very light. Plastic Logic will collaborate with Toppan printing to bring these new displays to the market.

The two companies will find new applications in the signage market. This display can be hung like a poster, has very low power consumption (it's non-volatile and only requires power to change the image) and is readable outdoors. Apparently the first application will be used as information signs that can provide disaster-related information in an emergency situation where battery-operation is required.

The UK's Technology Strategy Board (TSB) is funding 43 new projects under the ‘Technology Inspired Innovation’ R&D competition. Plastic Logic will participate in two of these projects, both related to OLEDs. The first one aims to develop new high-performance amorphous polymers, and the second called ROBOLED aims to integrate organic thin-film transistors (TFTs) backplanes with OLED frontplanes. Plastic Logic is collaborating with the UK's CPI on this project.

Back in January 2011 Plastic Logic received $700 million in funding from Russia's RusNano fund - to build a mass-production factory for thin, light and flexible plastic-based e-paper displays. The company recently withdrew from the e-reader market, and is now focused on technology licensing.

The Holst Centre and imec announced a new high-resolution flexible OLED displays research program. This new program builds on the existing research fields such Organic and Oxide Transistors and Flexible OLED lighting. The new program aims to develop an economically scalable route to flexible AMOLED mass production, facing challenges such as high resolution, low power consumption, large area, outdoor readability, flexibility and light weight.

The partners will develop a mechanically flexible encapsulation film and TFT backplane, a printed high-efficiency OLED, new materials and processes that will allow cheaper production at better quality and driver design. They will also develop a new manufacturing equipment such as fine patterning equipment for backplanes and tools for integrated roll-to-roll manufacturing. This new program follows up on the FLAME project. Above you can see a prototype Polymer-Vision made flexible OLED made together with imec and the Holst Center.

A couple of weeks ago we reported about new organic-TFT developed by University of Florida researchers, and now we've got some more info. The new transistor design is carbon nanotube based and it can efficiently drive the high-currents OLEDs need, at lower voltages than other designs.

The researchers not only designed a new transistor, but they combined it with emitting materials into a single design, called an OLET (we first reported about OLETs back in May 2010). The new design is called a CN-VOLET (Carbon Nanotube Vertical OLET). They say that this new design is more than eight-times more efficient than other competing devices. It also exhibits longer lifetime and should be easy to manufacture.

Researchers from the University of Florida developed a new OTFT for AMOLED displays. The new OTFT has a novel stacked vertical structure that automatically gives a large gate area. A thin gate can be achieved by spin-coating or other techniques. They say that 200µm resolution is sufficient to lay out the drain electrode which is the most demanding feature, compared with 25µm needed for some lateral TFTs.

The team prepares a paper that is due very soon to explain the new OTFT. There are still challenges of course to overcome in this design.

Sony published an interesting interview with their display unit team about rollable OLED displays. Back in May (during SID 2010) Sony unveiled a new 4.1" rollable OLED display (with 423x240 resolution at 121ppi, 16.8 million colors - and the whole thing is just 80um thick). In the interview, Dr. Kazumasa Nomoto reveals that Sony's end target is a rollable large-screen OLED TV: "The time will come when the very idea that an enormous black box (TV) was ever placed in rooms will seem strange."

In the interview, the team discusses the new technologies that Sony created for this new display. First was a new Organic TFT based on a new material: a peri-
Xanthenoxanthene (PXX) derivative (this took Sony 5 years to develop!). Sony also developed a flexible gate driver circuit. Finally, an insulating layer for the O-TFT and OLED materials using flexible organic materials. Those three technologies enabled sony to create a rollable video display.

Sony is showing a beautiful 4.1" flexible-rollable OLED display at SID - with 423x240 resolution (121ppi), 16.8 million colors and a 1000:1 contrast ratio. It's only 80um thick. Today they revealed some more technical details.

Sony said that the most distinctive technological feature of the panel is the organic semiconductor material "PXX (peri-Xanthenoxanthene) derivative," which Sony developed. The OTFT has a carrier mobility of 0.4cm²/Vs (four times higher than that of pentacene, which is commonly used). As a result, it became possible to use organic TFTs to form a gate-driver circuit on a resin substrate. Because there is no need to embed a driver chip, the entire panel can be folded. Sony did however embed a driver chip (it isn't easy to form a source driver circuit on a resin substrate) - and so the OLED on display can be folded only to one side.