Electronic Design

Projects And Partners Move OLEDs Closer To The Spotlight

Developments in organic light-emitting diode (OLED) technology are accelerating. Delivering its “final milestone,” the Organic LEDs for ICT and Lighting Applications (OLLA) organization has unveiled what it is calling Europe’s most efficient OLED lighting tile.

Also on the other side of the Atlantic, Osram Opto Semiconductors is leading the charge to develop lower-cost volume production methods for OLEDs. The company is a principal player in a European funded R&D program, dubbed the CombOLED project, that plans to merge unique structures, manufacturing strategies, and less complex materials to achieve cost-effective OLED lighting products.

And with goals similar to CombOLED, the U.S. Display Consortium (USDC) and Plextronics have partnered to introduce a hole-injection-layer technology that promises to push OLED displays into wider commercial markets.

Founded in October 2004 and led by Philips Lighting, the OLLA project consists of 24 partners, industrial companies, universities, and research institutes spread across eight European countries. Now, the project ends its 45-month run by presenting the basic technology for a white OLED light source.

Based on Novaled’s PIN OLED technology, the light source specifies an efficacy of 50.7 lumens per watt at an initial brightness of 1.0 cd/m2. According to Martin Vehse of Novaled, “PIN OLED technology has the potential to further improve the power efficiency. It’s in line with the technology roadmap that in the near future some 100-lumens-per-watt OLEDs will be achievable.”

Apparently OLLA hit its initial goal to develop an OLED light source capable of an efficacy of 50 lumens per watt with a lifetime of more than 10,000 hours at an initial brightness of 1.0 cd/m2. The partners also reached project targets in color rendering, and the lifetime of the Novaled device exceeds the target value by one order of magnitude.

OLLA presented the results of its labors at a recent public event in Eindhoven, the Netherlands (Fig. 1). The OLED lighting tile measures less than 2 mm thick and employs a metal line grid to generate homogeneous light output across the entire surface. In addition to the tile, OLLA also demonstrated the first large ITO-free (indium-tin-oxide) OLEDs, the first large-area printed OLEDs, and several IC technology demonstrators.

As the project closes, Philips, Osram Opto Semiconductors, Siemens, Novaled, and Fraunhofer IPMS will continue developing OLED lighting technology as participants in another European venture, the OLED100.eu project. For more details and a wrapup, visit www.hitech-projects.com/euprojects/olla/.

Osram Opto Semiconductors will lead the European-based CombOLED research project, whose aim is to achieve costeffective OLED lighting solutions in volume-production environments.

“The objective of the CombOLED project, which is being funded by the European Union and coordinated by Osram, is to create the necessary conditions for introducing the new light sources into lighting applications,” said Bernhard Stapp, head of solid-state lighting at Osram.

The initial challenge that project participants face is developing a low-cost process and device architecture to make OLEDs market-competitive. The second challenge involves the printing of unique component architectures for large-format transparent light sources.

The project will look into finding a more economical substrate than ITO-coated glass. It also will investigate stack technology that involves less complex deposition methods as well as other methods capable of depositing organic-material layers at high speeds. And, it will research a top-side contact that is transparent to visible light.

According to Osram, CombOLED extends and builds on insights and developments of the OLLA project. Advances in the materials research extending from OLLA efforts include a 15- by 15-cm demonstrator based on light-emitting polymer materials and a 10- by 10-cm2 white OLED, which may lead to further developments (Figures 2 and 3). For details, visit www.comboled-project.eu.

The result of a partnership between the U.S. Display Consortium (USDC) and Plextronics, a unique hole-injection-layer (HIL) technology may lead to high-performance, low-cost OLED displays for mainstream commercial markets. The partners expect the HIL technology to enhance device performance by reducing surface roughness, improving charge injection, and allowing fine-tuning of work functions.

The material, developed by Plextronics, takes a different approach to conductive polymer chemistry that appears to deliver significant performance improvements over past methods. The resulting material, called Plexcore OC, promises to be a cost-competitive and a suitable replacement for currently used polyethylenedioxythiophene polystyrene sulfonate (PEDOT PSS) materials.

“Our company has added significant in-house capabilities to allow scale-up for our new Plexcore OC as a result of our collaboration with USDC,” said Shawn Williams, vice president of technology at Plextronics. “Also, we have successfully implemented Plexcore OC in partner devices, and the material has been tested in newer device architectures.”

In addition to OLED cell-phone displays and signage, plus flexible OLED displays, Plexcore OC finds employment in printed solar cells and organic photo detectors, smart labels, and fieldeffect transistors. For more details, visit www.plextronics.com.

TAGS: Components
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