by Jeffrey Spindler
The term "solid state" is defined by Webster as "relating to the structure and properties of solid material" and "using semiconductor devices rather than vacuum tubes." LEDs and OLEDs are solid-state semiconductor light-emitting diodes that are expected to be more durable than conventional incandescent and fluorescent light sources due to their solid structure of inorganic or organic layers. In addition to their less-fragile nature, LEDs and OLEDs have already met or exceeded the performance of fluorescent lighting in terms of efficacy, lifetime, and color while further offering environmental benefits such as elimination of mercury. These next-generation light sources have enormous potential for energy savings due to their high efficacy and long lifetime. Governments and industries around the world have recognized these fundamental benefits and are aggressively pursuing research and development in solid-state lighting (SSL).
LED technology has made tremendous progress and is already appearing in many commercial applications such as signage, automotive, backlighting for displays, and general illumination. OLEDs are several years behind, but the technology is quickly catching up in terms of performance. It is likely that both of these technologies will succeed due to their complementary nature, with the LED being a point source and the OLED a planar, diffuse light source. Like any new technology, there are many hurdles to overcome before widespread adoption of SSL, both technical and economic.
Kodak's 6 x 6-in. prototype OLED lighting panels with 50-lm/W efficacy, 3000K warm-white emission, and high-quality color rendering (CRI = 85) illuminate objects such as a MacBeth color chart and several fishing lures to demonstrate color-rendering quality.
This issue of Information Display will focus on the emerging field of solid-state lighting. My colleagues and I from Kodak provide an overview of next-generation SSL technologies with a focus on OLEDs. We discuss the current state of the art in SSL technology, as well as some of the barriers to commercialization and what is being done to overcome them. The next article from Chris Eichelberger (OSRAM Opto Semiconductors) discusses the latest trends in LED technology and standards development, as well as the application of LEDs to general lighting. In the third article, Graham Upton and colleagues from Endicott Research Group (ERG) describe the challenges that have been faced in designing LED drivers for backlight applications, and the new challenges that will be encountered in designing LED drivers for SSL applications such as general illumination.
Having been actively involved in OLED research and development for the last 10 years, it is exciting and refreshing to see another market emerging for OLED technology beyond displays. I've been impressed with the rapid performance improvements in white-OLED technology over the last few years, as well as the number of high-quality OLED lighting prototypes that have been displayed at recent trade shows such as Display Week 2009 and FPD International. The adoption of LED backlights into LCDs has been equally as impressive, allowing for smaller and lower-power mobile devices and thinner LCD-TV displays with higher performance than their CCFL-backlit counterparts. These trends have resulted in the SID Technical Program Committee devoting a technology track to SSL at the 2010 SID Symposium, and, of course, this year's very first issue of Information Display focusing on SSL.
I hope you find the articles in this issue interesting and thought-provoking. May you be enlightened by the realm of possibilities and the promise that solid-state lighting holds for our future, as we stand at the forefront of the lighting revolution. •