Background information: Red and green light-emitting diodes (LED) have been with us for almost half a century, but not blue LED
By Don Lincoln on Thu, 09 Oct 2014
In the early hours of October 7, 2014, … The Nobel Committee often recognizes grand discoveries, like the prediction of the Higgs boson and the observation of the accelerating expansion of the universe. Thus many were surprised to see the 2014 prize honor a very practical invention: blue light emitting diodes. …
The technical achievement
LEDs are one of many useful spinoffs from the basic science of quantum mechanics. In the standard quantum cartoon, electrons orbit the center of atoms, kind of like planets around the Sun. (The planetary model is not completely accurate, but it has many good features that help visualize what is going on in the quantum realm.) Imagine a simple atom with a single electron. According to quantum mechanics, the electron can be in a series of discrete orbits, as if a single planet around our Sun could be in the orbit of Mercury or Venus or any of the planets, but nowhere in between. Electrons near the nucleus have lower energy, while ones farther away have more energy.
When an electron moves from a high-energy orbit to a lower-energy one, it emits energy in the form of light. The color of the emitted light depends on the energy difference between the old orbit and the new one. The bigger the energy difference, the bluer the light.
The greatest benefit on mankind
To understand why this seemingly mundane development warrants such recognition, one must return to Alfred Nobel’s will, in which he provided the seed money to start the prizes that bear his name. When Nobel’s brother died, a French newspaper mistakenly published Alfred’s obituary. Alfred Nobel was horrified to see himself called a “merchant of death” and a man “who became rich by finding ways to kill more people faster than ever before.” He resolved to repair his legacy by bequeathing a prize to be awarded to “those who…have conferred the greatest benefit on mankind.” Nobel wanted to be remembered as a man who helped make the world a better place.
This year’s award clearly fits the bill. “I really think that Alfred Nobel would be very happy about this prize,” said Per Delsing, head of the Nobel Committee for Physics, in announcing the prize. ”It’s really an invention and it’s really something that will benefit most people.”
The invention of bright blue LEDs brought entirely new industries into existence. Now, blue, red and green LEDs could be combined to make white—or any other color—light. This development led to the power-efficient screens for cell phones, TVs, computers, iPads, and many other electronic miracles of the modern world.
However the real impact of blue LEDs goes well beyond our rainbow-colored gadgets. Today, LEDs are bright enough to use as light sources. Just as Thomas Edison’s original incandescent light bulb revolutionized the early years of the 20th century, LEDs are poised to revolutionize the 21st.
LEDs can now emit far more light using far less power than incandescent and fluorescent bulbs. For instance, an incandescent light bulb can emit about 16 lumens per watt of electrical power, and a fluorescent light manages about 70 lumens per watt. In comparison, a modern white LED can emit 300 lumens per watt, meaning that it consumes only about 5% of the power of an incandescent. Given that about a quarter of the world’s electricity is used to generate light, the invention of efficient lighting can have considerable economic and environmental impact, potentially reducing the greenhouse gas emissions that are driving anthropogenic global warming. In the developing world, bright, efficient LEDs could provide solar-powered, off-grid energy for homes, hospitals, and more.
This year’s Nobel Prize in physics is very well deserved and reflects Alfred Nobel’s desired legacy of recognizing discoveries and developments that have greatly benefited mankind.