History & Background Information of Solid State Lighting

Solid-state lighting (SSL) refers to a type of lighting that utilizes light-emitting diodes (LEDs) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps), or gas.

The term "solid state" refers to the fact that light in an LED is emitted from a solid object—a block of semiconductor—rather than from a vacuum or gas tube, as is the case in traditional incandescent light bulbs and fluorescent lamps. Compared to incandescent lighting, however, SSL creates visible light with reduced heat generation or parasitic energy dissipation, similar to that of fluorescent lighting. In addition, its solid-state nature provides for greater resistance to shock, vibration and wear, thereby increasing its lifespan significantly.

The first commercial LEDs were commonly used as replacements for incandescent indicators and in seven-segment displays, first in expensive equipment, such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators and even watches. These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area. Later, other colours became widely available and also appeared in appliances and equipment.

As the LED materials technology became more advanced, the light output was increased, while maintaining the efficiency and the reliability to an acceptable level. The invention and development of the high power white light LED gave rise to the possibility to use for illumination.

The first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation for which he was awarded the 2006 Millennium Technology Prize for his invention.

he development of LED technology has caused their efficiency and light output to increase exponentially, with a doubling occurring about every 36 months since the 1960s, in a similar way to Moore's law. The advances are generally attributed to the parallel development of other semiconductor technologies and advances in optics and material science.