The Nobel Prize in Physics was awarded on Tuesday to scientists who developed blue light emitting diodes (LEDs). These blue lights faced several challenges in their development but helped advance LEDs toward a significant accomplishment: creating white light.
LED lights are renowned for their longevity, efficiency, and ability to conserve energy. The first practical LEDs — LEDs that emit enough light to be used in real-life applications — were developed in 1962 and were red. Green LEDs followed several years later. However, almost 30 years passed before the Nobel scientists — Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura — invented practical blue LEDs. But, what took so long to make blue LEDs and what makes these lights more remarkable than LEDs of a different color?
Gallium nitride (GaN), aluminum gallium nitride (AlGaN), and indium gallium nitride (InGaN) – alloys that were eventually used in practical blue LEDs, were developed over three decades. GaN was originally identified as a candidate with appealing optical properties in the 1950s. However, it took until 1986 for researchers to grow the large, high-quality GaN crystals needed for multilayer electronic devices. Advancements in the other two materials followed shortly after. The first viable blue LED was demonstrated using a combination of these three alloys in 1994, after years of testing material combinations and device architectures.
The advances in materials science and engineering are remarkable and help to realize the real impact of blue LEDs: their use in lighting systems. Before practical blue LEDs, it was impossible to generate white light with LEDs. Now, there are many ways, such as combining red, blue, and green LEDs (as illustrated in the infographic). Thanks to the development of blue LEDs, LEDs that emit white light are now used in a wide array of devices, such as streetlights, light bulbs, flashlights, and televisions. Some models of white LED lamps are 83 percent more efficient at converting electricity to light than conventional incandescent light bulbs.
There are additional benefits to generating white light using LEDs instead of incandescent or fluorescent lamps, including:
- Lower greenhouse gases: In 2012, the U.S. generated roughly 2,000 million metric tons (CO2 equivalents) of greenhouse gases from electricity production. Lighting our buildings and surroundings accounts for 12 percent of electricity usage — roughly 240 million metric tons of greenhouse gases. If every incandescent light bulb was replaced with the most efficient LED bulb on the market, greenhouse gas emissions could be reduced by 20 million metric tons. This equates to removing 9 million cars from the road.
- Less mercury in the environment: Compact fluorescent light bulbs contain a small amount of mercury (~3 mg) that can be released into the environment if the bulbs are not disposed of properly. LED lamps do not contain mercury and consume less electricity.
- Less material waste: LED lamps have four to five times the lifespan of fluorescent lamps and 40 times the lifespan of incandescent light bulbs. This means LED light bulbs are replaced less often, which reduces the overall material waste generated by light bulbs.
The capability to generate more efficient, longer-lasting light bulbs is what makes blue light so special. Light bulbs using LEDs still require a significant upfront investment – a single light bulb can cost as much as $50. Research efforts continue to reduce the upfront costs to encourage wider adoption.