For centuries man lit his night with an oil lamp that created only about 1/10th of a lumen per watt (a very small amount of light produced for the expenditure of a standard unit of energy). Then in the late 19th century the incandescent light bulb was invented and that eventually provided about 16 lumens per watt. In the late 1930s the fluorescent lamp became a reality and gave us an amazing average efficacy of about 70 lumens per watt. Now in the early 21st century still another revolutionary development is taking place – light emitting diodes (LEDs) are giving or will soon give us 300 lumens per watt. Think about the amount of change in the way we have lit our homes, offices, stores, factories, and streets in just the last 20-30 years. It is nothing short of astonishing and you can bet that more change is on the way in how we light the way we live.
The very first LEDs date back to 1907 but like most technological changes it took plenty of time, trial and error, lucky discoveries, and manufacturing prowess to develop the fledging LED from a purely theoretical understanding into practical usefulness. In the beginning very few colored LEDs were available – especially the all-important blue LED.
The Power of Blue
Now, why is the blue LED so important? Quite simply because there are no white LEDs. The white light that our eyes detect is created by using a blue LED and some yellow phosphor. The yellow phosphor coating may be placed directly on the blue LED or on the glass envelope that houses the blue LED. Either way when the blue light from the blue LED passes through the yellow phosphor the resulting light appears to be white.
In late 2014 at the Nobel Prize Award Ceremony in Stockholm, Sweden, the three Japanese scientists who developed the blue LED while working at Nichia Chemicals will share the Nobel Prize in Physics for their work on the blue LED. In official terms the Nobel Committee awarded this year’s physics prize to Isamu Akasaki, Hiroshi Amano, and Shuji Nakamura “for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources.”
Furthermore, the Nobel Committee pointed out in its announcement that the results of all the scientists’ hard work will be on display everywhere as the three recipients make their way through Stockholm: “the light from their invention will be glowing in virtually all the windows of the city.” And they can be assured that, as this century progresses, the ascendancy of the LED will only become more dramatic.
Top Image via The Royal Swedish Academy of Sciences