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Development of LED Light Bulbs


The development of LED Technology started in 1955 when Rubin Braunstein of the Radio Corporation of America (RCA) reported on infrared emissions from gallium arsenide (GaAs) and another semiconductor alloys. Such knowledge had already existed since a report on infrared emissions from another semiconductor in 1907 by Henry Round of Marconi Labs; but no practical use was made of the discovery for several decades.


In 1920, Oleg Vladimirovich Losev, a Russian scientist, reported the creation of the first LED without any knowledge of Henry Round's report. His research was distributed in Russian, German and British scientific journals, but no practical use was made of the discovery for several decades.

After Rubin Braunstein's report on his discovery, scientists started to study this technology seriously. The first practical visible-spectrum (red) LED was developed in 1962 by Nick Holonyak, while working at General Electric Company.

However, the first LEDs only emitted low light and could not be used alongside other lighting technologies because the light output was not enough to illuminate a significant area. These red LEDs were only bright enough for use as indicators, such as putting in electronic appliances as an indicator of on-off status. The scientist who solved this problem was Shuji Nakamura of Nichia Chemical, Japan, who invented the first high-brightness blue LED bulb.

The high-brightness blue LED was developed in GaN nucleation on sapphire substrate. The existence of blue LEDs and high-efficiency LEDs quickly led to the development of the first white LED, which was enough to illuminate a significant area in 1992. At present, as semiconductor technology has got more advanced, LED technology has also grown alongside. There are wide ranges of usage in such appliances as calculators, traffic lights, headlights, traffic boards, torches, lighthouses, cinema screens, etc. In addition, the LCD light on a mobile phone screen is illuminated by LED.


In the future, LED light will also be used in aviation. Australian airline Quantas Airways started to use LED light bulbs in its first class cabin, by turning on a blue light LED when the passengers are sleeping. In addition, Boeing is planning to decorate the passenger cabins of its 787 Dreamliner aeroplane, which will be launched in the near future.

Meanwhile, the government in various countries promoted the benefits of switching to the LEDs due to its high energy efficiency. For example, the Ministry of Economic Affairs of Taiwan announced in April 2007 that they had spent NT$2.1 billion in order to switch traffic lights to LEDs within three years.

Furthermore, our street lights shall be switched to LED. White LED lamps have achieved market dominance. The growth of LEDs in the market is both rapid and steady, from USD 122 million in 1995 to 3.9 billion in 2005. In the near future, the growth may be up to 25% per annum. More than 52% of LED lamps have achieved market dominance in applications where high efficiency is important at low power levels. Some of these applications include the screens of mobile phones, digital cameras, etc. Furthermore, 14% will be used in digital signage and big screens and 14% in automobiles. Japan is the top country in the LED market and Taiwan ranks second. Combined, the production capacity of both countries are more than 2/3 of the world's market. The leading LED companies are Nichia Corporation and Toyoda Gosei of Japan, and Cree, Inc. of the USA.

Advantages of LEDs

- LED emits 170 lumen/watts light, more than 15 lumen/watts higher than the incandescent light bulb. Fluorescent tubes emit 80-100 lumen/watts.

However, the fluorescent tubes waste light by emitting visible light in all directions, while LED emission tends to be only in one direction. The result is that LED emits 70 lumen/watts visible light more than the 100 lumen/watt of the fluorescent tubes. LED technology is developing rapidly and will be more advanced than fluorescent technology in the near future.

During the past few years, LEDs have developed rapidly from 5 lumen/watts in 1996 to 50 lumen/watts in 2006, and 70 lumen/watts in 2007. In 2009, Nichia Corporation in Japan announced their success in developing the 150 lumen/watts LEDs.

- Advantages claimed for LED light bulbs are that they are mercury free, unlike a compact fluorescent lamp.

- We have the ability to control the emission of LED lights. Therefore LEDs can be useful in the light systems of various landmarks. For example, the Grand Louvre in Paris uses LED light in the lighting system for the Mona Lisa because LED light does not contain infrared or ultraviolet which could damaged the painting.


- LED light output rises at lower temperatures, which benefits the heating systems in buildings as they use less energy in air conditioning, thus promoting energy savings.

- Average rated lifetime of 100,000 hours or 11 years, which is much longer than an average rated lifetime of 30,000 hours of fluorescent tubes and an average rated lifetime of 1,000-2,000 hours of incandescent light bulbs.

LED light bulbs have no glass tubes to break, unlike fluorescent tubes and incandescent light bulbs, and their internal parts are rigidly supported, making them resistant to vibrations and impact, thus suitable for aviation and automobiles.

- LED light bulbs are suitable for applications that require the ability to instantly turn them on and off. The lifetime is unaffected by constantly switching them on and off, unlike fluorescent tubes. Once turned on, LEDs emit instant light.

Although LED lamps have achieved market dominance in appliances, they are not used as a lighting system in households due to their limitation of emitting genuine visible white light. At present, there are two primary ways of producing white light-emitting diodes, as follows:

- The simplest and easiest was invented by Nichia Corporation by coating a blue LED with sapphire substrate. However, the disadvantage of this mechanism is wasted energy and the reduction of luminous efficacy.

- The Effective method that boosts luminous efficacy is to use individual LEDs which emit three primary colours - red, green and blue - and then mix all the colours to form a white light. Nevertheless, this method is particularly interesting for many uses because of the flexibility of mixing different colours and, in principle, this mechanism also has higher quantum efficiency in producing white light. However, the disadvantage of this mechanism is the complication and high maintenance cost due to large quantities of LED light bulbs being needed for light sources.

Another disadvantage is that the prices of white LED light bulbs are higher than fluorescent tubes. However, research and development of LED technology is more advanced. By 2010, experts predicted that the manufacture cost of white LEDs shall be equal to fluorescent tubes, which would enhance the expansion of the LED market.

Thus, the lower of cost in manufacturing white LEDs to be equal to fluorescent tubes is unnecessary. Although LED light bulbs cost more per unit, the assembly of LEDs is far simpler than the fluorescent tube, which requires additional equipment. If the LED light bulb price is slightly higher than the fluorescent tube, the total cost in setting-up an LED lighting system will be lower.

In producing LED white light, governments in various countries encouraged the research and development in order to rule out the manufacturing cost restriction. The USA government is currently funding the "Next Generation Lighting Initiative", which is research and development that aims to increase the LED white light to be three times more effective by 2025.

If such research is successful, LED lamps will be widely used because of their high energy efficiency. Since 1993, LED white lights started to be used in lighting appliances such as torches. This is to show that the appliance manufacturer started to acknowledge the efficiency as well as accepting the cost of LEDs.

Development of LED Light Bulb

Generally, LED light bulbs can emit only a single coloured light (as well as a single frequency or single wavelength). Thus, there are attempts to find techniques to produce white light. However, there are two primary techniques of producing white light-emitting LEDs, which are: the wavelength conversion technique; and the colour mixing technique.

Wave Length Conversion

This technique works by using the luminous phosphor to change some part, or all, of the wavelength to convert it to a source that produces visible light, and which contains the three following methods:

1. This method requires a combination of blue LED light with yellow phosphor, which absorbs a portion of the blue light and emits a broader spectrum of white light. This technique produced the lowest manufacture cost and is widely used in LED manufacture at present. The technique was developed by Nichia Corporation, Japan.

2. This method requires the uses of multiple LED chips in close proximity, each emitting a different wavelength to generate the broad spectrum of white light. The advantage of this method is that the intensity of each LED emits better quality white light. However, the major disadvantage is the high production cost.

3. This method requires the use of LEDs emitting white light from a UV-illuminated phosphor, by using the UV converted illuminated phosphor to emit a combination of white light. This technique is the same technique used in the manufacture of fluorescent lamps.