LEDs have caused quite a revolution in lighting so far and, since the advent of a practical blue emitter, have had even more of an impact in the display arena. Massive LED HDTV screens are really the ultimate embodiment of large format displays and LED's now dominate this field. But most of the LED buzz is in lighting and that's where the most opportunities for improvements lie.

Despite all the hype, LEDs are not currently all that efficient. They make light at about the same efficiency as a halogen lamp. And they certainly don't produce light without making heat. It's the heat generated within the LED die itself that creates some major limitations. Heat, and more specifically, the temperature of the die, has a drastic effect on the LED's lifetime, its color and the amount of light it generates at a given current. Most people don't understand that the LED manufacturers' specs rarely give the luminous output for their products when excited by a continuous current. The efficiency specs are usually published for pulsed current operation so as to maintain a constant 25ºC junction temperature. 25ºC, or room temperature, is almost impossible to maintain with an LED junction in practical applications, even with a massive heatsink. We need a more realistic set of specifications from the manufacturers and improvements in the LED materials allowing higher temperature and more efficient operation.

The wide range of colors available from LEDs and LED arrays is fantastic. However, the one most important color, true white, is still unavailable. White LEDs are in wide application for task lighting and sign illumination and other non color-critical uses where color rendering and color match is not important. But LEDs have not gained wide acceptance for shop lighting of products like clothing, produce and art where color rendering is paramount. Light produced by the current generation of white LEDs looks a lot like that made by poor fluorescent bulbs. LED manufacturers must improve the color rendering or quality of the light from white LEDs if they are to be accepted widely by consumers. After all, poor light quality is one of the major obstacles to wider usage of the compact fluorescent bulb.

Costs are still high with LED light sources. Both the initial cost of installing as well as the cost of operating LEDs puts them well behind sources like CF or metal halide. Costs have been coming down with volume and process improvements but the rate of cost reduction has been decelerating. On the positive side, LEDs do not contain mercury or other harmful agents. However, the side stream from the manufacturing process has to be dealt with carefully. I would urge manufacturers to reduce costs and contaminants from their processes.

Organic LEDs, or OLEDs, may soon alleviate many of the shortcomings of the current semiconductor devices. OLEDs show promise in reduced cost and increased efficiency. Their potential application in the display field is almost limitless and may someday replace that big screen LCD or plasma TV you just bought. The first industrial displays are just beginning to show up in the OEM market and they look unbelievably crisp, bright and thin. Since OLEDs can potentially be printed like an ink, they may be the real revolution that we're looking for. To quote a dear friend and fellow lighting enthusiast: "LEDs are the future of lighting and always will be!"

- Jim Bornhorst