How the quest for blue LEDs put white in a new light

While last year's Nobel Prize in Physics was for an esoteric advance in knowledge - theoretical work on sub-atomic particles, notably predicting the existence of the Higgs boson - this year's was for far more practical achievements, by three Japanese-born men: Isamu Akasaki, Hiroshi Amano and Shuji Nakamura. Each played a seminal role in the invention of blue light-emitting diodes.

Such diodes proved the key to creating white LEDs, and to making a full spectrum of colours on LED displays - including smartphone screens, along with modern televisions and computer monitors.

Light-emitting diodes - LEDs - produce light directly from electricity, rather than heating filaments as in light bulbs of the kind first commercialised by Thomas Edison in the late 19th century. Light emission from a diode was first reported in 1907, when electrical engineer Henry J. Round noted that some silicone carbide crystals gave out a yellowish light as he applied a voltage to them.

This week, news reports have included 85-year-old Professor Nick Holonyak remarking on being overlooked for a Nobel prize for his seminal work on inventing the first visible light-emitting diodes, in the early 1960s. These diodes emitted red light, and in tandem with a red laser diode that Holonyak helped invent they made possible technologies such as fibre-optic networks and DVDs.

The red LEDs came after the advent of LEDs emitting infrared, which became commonplace in applications such as television remote controls. Green LEDs appeared in the 1960s. There were blue LEDs, made from silicone carbide, but they were feeble.

The need for efficient blue LEDs was recognised by people such as James Tietjen, director of the Materials Research Division of the Radio Corporation of America. In 1968, he realised the potential for developing a flat panel television that could be hung on the wall like a painting. The red and green LEDs existed; all that was needed was a bright blue LED.