Electronic Design

OLED Technology Marches On

One of the most promising and exciting light-emitting technologies is the organic light-emitting diode (OLED). Many experts predict it will overtake nearly all display technologies, including LEDs, when it matures.

Eastman-Kodak Co. was very instrumental in discovering OLED technology in the early 1980s. It's come a long way since then. Thanks to technology advances, the OLED has now proven viable as a light source for backlighting and other applications. In fact, some OLEDs are already built into display screens for cameras, DVD players, and cell phones. OLEDs can be printed on many types of thin substrates, forming lights that bend and function in backlighting applications.

A few more vivid colors are possible with OLEDs versus liquid-crystal displays and other technologies. They offer a wider viewing angle of up to 1608, and they require no backlighting. Most importantly, they require much less power than other display technologies-crucial for battery-operated devices.

That said, OLEDs still aren't a mature technology. For OLEDs to become more widely successful, significant advances must be made in device efficiency, lifetimes at high brightness levels, high-throughput fabrication processes, and illumination-quality white light. Major R&D efforts are underway worldwide to build that technology bridge. Ultimately, OLEDs must reach efficiencies of more than 100 lumens/W to widely compete as lighting sources.

The U.S. Department of Energy (DoE) is heavily involved in research funding for OLEDs when it comes to illuminating homes, offices, buildings, and industrial plants. It believes that switching conventional lighting sources to solid-state devices could slash the nation's electric power consumption by a third.

Part of the DOE's funding for this effort includes a $2.4 million award to Universal Display Corp. The company is working with researchers at Princeton University to develop high-efficiency phosphorescent OLEDs (PHOLEDs). They're investigating a maskless deposition process called organic vapor jet printing.

Working with scientists at the University of Southern California, Universal Display, and Princeton University also developed a PHOLED with a record efficiency of 20 lumens/W. This was achieved by lowering the drive voltages and increasing the amount of light extracted from the PHOLED die.

Meanwhile, more than 20 of Europe's leading companies and research establishments are taking part in an OLED R&D project. Called OLLA, which stands for high-brightness Organic Light-emitting diodes for ICT and Lighting Applications, the project seeks to demonstrate long-life and high-efficiency, high-brightness white OLED tiles for use in general lighting applications by 2008. (ICT stands for information and communication technologies.) The project is shooting for 10,000-hour lifetimes and 50-lumen/W efficiencies.

Another exciting form of OLED technology, flexible OLEDs (FOLEDs), are manufactured from transparent plastic films or other lightweight materials filled with special polymers. Prototype rollup FOLEDs already exist.

Cambridge Display Technology is a pioneer in polymer OLEDs (P-OLEDs). The company holds key patents in the areas of materials development, device optimization, and manufacturing process development. It also holds sublicensing rights to an extensive portfolio of patents relating to P-OLEDs, which belongs to the Seiko-Epson Corp.

Plus, an Israeli research team at the Technion Institute of Technology has manufactured new organic semiconductors that use proteins designed in the lab. They're linked together to create electronic-grade peptides. The team believes this could lead to full-color foldable LED displays that can be rolled up-with higher resolution than what's available from today's computer screens-within the next few years.

TAGS: Components
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