Solid-State Lighting

A Compact, Durable and Efficient Source of Targeted Light

Solid-state lighting (SSL) is a type of lighting that uses semiconductor light-emitting diodes (LEDs) as a source of light instead of filaments, plasma or gases. SSL’s unique characteristics, including compact size, long life span, directional lighting, and lack of infrared or ultraviolet emissions, make it more energy efficient than traditional lighting technologies, resulting in lower overall emissions.

The Technology

The first LED was invented and demonstrated more than 50 years ago. Unlike other lamps (e.g., fluorescent), LEDs are not inherently white light sources, making them more suitable for colored light applications such as backlit mobile devices, traffic signals, backlit signage, and automotive stop and indicator lighting. It was not until 1995 that the first white LED (a combination of blue emitter and yellow phosphor) was demonstrated. LEDs did not become viable for general use lighting until high-power 1-watt LEDs were made available in the early 2000s.

LEDs create light through a process called electroluminescence. During electroluminescence, electrons are sent through the semiconductor material in the lamp to fill electron holes. When an electron finds a hole, it releases energy in the form of a photon (light). One of the defining features of LEDs is that they emit light in a specific direction, allowing LED fixtures to deliver light more efficiently to the intended location. By comparison, traditional fluorescent and bulb incandescent lights emit light in all directions, which can cause much of the light to be lost within the fixture, reabsorbed by the lamp or emitted in other nonuseful directions.

The Benefits

• Improved energy usage: A single SSL household luminaire consumes 85 percent less wattage than century-old light sources commonly used. The U.S. Department of Energy estimates that switching to SSL could reduce domestic electricity consumption by one-third by 2025, equivalent to the energy consumption of 20 million households.
• Improved environmental performance: Whereas traditional lighting sources — such as compact fluorescent lamps — contain mercury and need to be replaced every one to three years, SSL contains no mercury and can last up to 20 years, significantly reducing maintenance cycles and waste.

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