Nobel light

While I was preoccupied with the Chemistry Nobel on these pages recently, a physicist friend was suggesting last week that the inventors of the blue LED would be the most likely winners of the Physics Prize this year. He whimsically cited the fact that there were no "Higgs graphenes" discovered in the last year or so and that although the Nobel rules actually state the work for which a prize is awarded has to have been done in the last year, this is rarely the case (high-temperature superconductors excepted, Bednorz and Mueller in 1987).

Anyway, once again materials feature prominently as the Nobel committee decided to give the 2014 Nobel Prize in Physics jointly to Isamu Akasaki (Meijo University, Nagoya, Japan and Nagoya University, Japan), Hiroshi Amano (Nagoya University, Japan) and Shuji Nakamura (University of California, Santa Barbara, CA, USA) "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources".

I remember back in the day writing about the possibilities of blue LEDs, although the focus of my writing then was the polymer potential. Obviously, to make a white light source, blue has to be added to red and green light. Red and green light-emitting diodes were relatively easy. But blue remained elusive for many years. When Akasaki (born 1929), Amano (born 1960) and Nakamura (born 1954) produced the first bright blue light beams from their semiconductors in the early 1990s, their work would ultimately transform lighting and display technology. Akasaki worked with Amano at Nagoya, while Nakamura was employed at Nichia Chemicals, in Tokushima. They worked on alloyed gallium nitride devices (AlGaN and InGaN) with various dopants, primarily zinc.

If the twentieth century was lit by incandescent light it is possible that LEDs will illuminate us through the 21st century. The best white-light LEDs produce 300 lumens per Watt, which is much more energy-efficient than the 16 lm/W of the incandescent light bulbs that have their roots in the nineteenth century and even the 70 lm/W of a fluorescent tube. It is noteworthy that it was HJ Round at Marconi in 1907 who first demonstrated electrical light emission from a solid-state device. Modern LED white lighting usually uses a blue LED alone to excite a phosphor to generate white light, RGB LED lighting is still some way off. Nevertheless, these current devices have a lifespan of around 100 000 hours compared with the 10 000 hours of a fluorescent and the mere 1000 hours of an incandescent bulb. Moreover, their being much lower power means that they could light up parts of the world that lack access to a grid-based electricity supply, finding their power in inexpensive, but sustainable power generation - clockwork, solar, manual etc and displacing the noxious kerosene lamps prevalent in many remote and poor parts of the world.

Today, LEDs based on GaN are also the predominant back-lighting technology for illuminated LCD displays in laptop and tablet computers, many mobile phones, computer monitors, flat television screens. Additionally, blue and UV-emitting GaN diode lasers are used for high-density optical storage media, such as the aptly named Blu-Ray DVD. Future uses may see such UV-emitting AlGaN/GaN LEDs being used for water purification.

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".