LEDs Increasingly in the Market Spotlight

Light-emitting diodes (LEDs) made of GaAlA, InGalP, and GaP semiconductor materials give off light by transforming the energy released when electrons at a negative electrode fill holes at the positive electrode.

Thanks to advantages including compact size, low-voltage start, instant projection, and shock resistance, in the early stage of their commercialization LEDs were used as devices for displaying the status of electronic circuits. Today, the emergence of white-light diodes has led to new uses in the global lighting industry.

World heavyweight lighting manufacturers including Osram, GE, and Philips are working on the development of LED lamps. Private and public concerns in Taiwan, Japan, and mainland China are also enthusiastically involved in the development of the new lighting technology.

In Taiwan, under the guidance of the Industrial Development Bureau (IDB) of the Ministry of Economic Affairs (MOEA), the Energy & Resources Laboratories under the Industrial Technology Research Institute (ITRI), and the Cabinet-level Atomic Energy Council (AEC), the local lighting industry has long dedicated itself to developing energy-saving, environment-friendly products of the highest quality for consumer use.

LEDs are categorized as visible-light type and invisible-light type. For the former, the major technology for the future will feature full color, high brightness, and white-color light. LED lamps, which are produced in models that come under both categories, are expected to assume a significant portion of the lighting market because of their power-saving, compact-size, durability, and quick-start merits.

It has been over 20 years since Taiwan began developing LED technology. Today a complete industry is up and running, incorporating upstream, mid-stream, and downstream enterprises. The diligent efforts of all involved has resulted in Taiwan's emergence as the world's No. 2 supplier of LEDs in terms of output value.

In the visible-light category, low-voltage LED lamps have been widely incorporated into indoor lighting-display systems, while high- voltage lamps have been applied to outdoor- display and alarm systems. Invisible-light types are mostly used in household appliances and scientific-research instruments.

LED lamps are now also widely used in automobiles. Global annual demand for automobiles has now reached 53 million, and almost all are fitted with at least 100 diodes of varying color. Around 20% of new cars are also reinstalled with LED lamps as replacements for traditional-type lamps.

LED billboards and LED traffic-signal lighting have also seen the widescale introduction of full-color diodes.

The light emitted by white-light LEDs is still not as bright as traditional units. Nevertheless, white-light diodes offer superior color- rendering performance than red-light, yellow- light, and green-light diodes, making them suitable for day-to-day lighting purposes. "Color-rendering performance" is an index for measuring how true the colors of an object are rendered in the lamp's beam compared to their rendering in natural sunlight.

Currently, white-light LED color temperatures range from 4,000 to 1,100K--meaning the quality of the light is close to yellowish-white- -making this type of light an ideal replacement for many types of fluorescent lamps and incandescent lamps utilized in small areas

White-light LEDs are estimated to have a maximum service life of around 100,000 hours, and their brightness can be maintained at 50% even after burning 15,000 hours (sometimes as much as 40,000 hours).

These outstanding features have resulted in the countries of Europe, the United States, and Japan organizing dedicated research institutions to further develop white-light LED technologies.

Despite statistical differences among countries, an accepted fact is that lighting consumes around 20% of the world's total energy production every year. In 1995 the U.S. Department of Energy invited lighting specialists to participate in a conference aimed at identifying promising research areas for improving the efficiency of white-light sources and achieving major breakthroughs in lighting- source performance and efficiency.

Although white-light LEDs are attracting great interest from lighting manufacturers, application of such units to lighting fixtures has not yet reached the full potential because of a number of difficulties. The first is that luminance is still far below 100 lumens per watt, the brightness the average fluorescent lamp currently produces. The second is that LED light does not spread out in the same way as is the light given off by traditional lamps, instead being more direct.