Blue LEDs Light The Way To Top Nobel Physics Prize
‘It’s Nobel Prize time again and my favorite award, for physics of course, went to the inventors of the blue LED light for their achievement in the 1990’s which allowed the development of white LED lights which are poised to turn this century into one lit by LEDs just as the 20th century was lit by incandescents.
Congratulations to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for their critical achievement that had eluded all others for decades.
Light Emitting Diodes offer tremendous advantages over other common methods for producing light like the incandescent light-bulb. Right off the bat, they have no filament that can burn out and they do not get very hot. How many times have you touched a light-bulb in your house and uttered a curse word? In fact, only 10 percent of the current sent into an incandescent light-bulb actually goes into making photons. 90% goes into creating heat that makes everything in the immediate vicinity really hot (why else would an easy-bake oven use a light bulb as the heat source?). This is obviously very inefficient and fluorescent bulbs aren’t much better.
Geek Aside: Technically, 100% of the power of an incandescent bulb goes into creating heat if you consider that the light hitting the walls (and you) creates tiny amounts of heat when it’s absorbed
Efficiency then is one of the hallmarks of LED lighting. Here’s a quick comparison to put it into perspective
- Incandescent: 16 lumens per watt ( a lumen is a measure of the total amount of visible light emitted)
- Compact Fluorescent: 67 lumens per watt
- LED: 83 lumens per watt with projections of 150 by 2020.
The lifetime of an LED is also pretty crazy. They can last 50,000 hours compared to the life expectancy of an incandescent which is only 1,200 hours or so. This of course makes them much cheaper over the long haul and they’re getting cheaper all the time. Don’t forget that their expense is also reduced immediately upon use since a smaller amount of electricity can be used to run them. LEDs are also incredibly rugged (how many light bulbs have you broken? How many LEDs?…not a perfect comparison, I know). And finally, add to all this their tiny size and easy integration into electronics and you have one helluva product.
So how does this shit work? The key is the D in LED. Diodes are a simple type of semiconductor which is a material that can be tweaked to produce varying amounts of electrical current depending on the need. There are two semiconductor materials bonded together in a diode. One has extra electrons that can move around (N-Type) and the other has holes that electrons can move into (P-Type). This movement of electrons has the wonderful side-effect of emitting light. This happens because when an electron moves to a hole, it moves into a tighter orbit than previously which means the electron has less energy. That extra energy is released as light.
If the the drop in orbit is minimal, then the light release is so feeble that our eyes can’t even see it. This infrared light is exactly what the LED in your tv clicker releases to save us from having to get up from the damn couch. These Infrared light-emitting diodes were the first modern LEDs and we never looked back. As LEDs were tweaked and improved, more energetic light could be coaxed out of them, eventually producing red visible light in 1962. These were eventually used in electronics like indicator lamps, calculators and those lame watches when I was kid. Soon after red came organge-ish and yellow, followed by many others…except blue.
Always calling out to the researchers however was the siren song of the blue LED. They knew that blue would be instrumental in creating a white light (such as by combining the primary colors Red, Green, and Blue) and that these white light LEDs could revolutionize lighting technology. White light, however, was not the only benefit. This advance also meant that we had a new way to create all the other colors of light and a way to control them dynamically. This blue holy grail was accomplished in 1994 by those newly minted Nobel Laureates I mentioned above. They weren’t the first however. Other researchers had made them in 1971 and 1989 but they either had too little light output or had crappy efficiencies in the range of 0.03%. I bet those researchers are feeling pretty bummed right about now.
So I hope you’re enjoying your flat-screen LED TVs and your colorful smartphones and your currently expensive white LED light bulbs. If you’re thankful however, don’t forget to thank not just Isamu, Hiroshi and Shuji but all the other countless less well-known researchers who also made invaluable contributions to the modern and amazing LED.
Video: How LEDs Work
Image Credit: Steeph-K