The men who first created blue LEDs have won the Nobel Prize for physics. The blue light was necessary for more energy-efficient bulbs and displays.

Although working LEDs have been around for more than 50 years, not all colors became available at the same time. That’s because LEDs work by a semiconductor material glowing a color when an electrical charge passes through it. The visible color depends on the wavelength, which in turn depends on the material.

The first working LEDs were red (which you’ll see on very old calculator displays), with orange, yellow and green following on. These all involved finding and using the right compound materials: each contained gallium or aluminium (or both), with arsenic, phosporus and indium also featuring across the various colors.

Blue proved a particular challenge, hence the famous DeLorean time clock from 1985’s Back to Future having a red, green and orange display.

Scientists discovered that they could get the even-shorter wavelength needed for blue by using nitrogren in the form of gallium nitride, but they weren’t able to grow big enough crystals to create a LED. The Nobel committee notes that many large firms explored the problem and abandoned work on it when they couldn’t get results.

Isamu Akasaki and Hiroshi Amano of Nagoya University stuck with it and, in 1986, came up with the idea of using materials including sapphire as a substrate. Four years later Shuji Nakamura of Nichia Chemicals developed a way to use temperature control to make the gallium nitride growth process more efficient. All three men have been awarded the prize.

Blue wasn’t the final color of the spectrum achieved in LED form (violet LEDs are available) but it was the most important. It made it possible to combine red, green and blue LEDs, which was the simplest way to produce a white light. Today the more common solution is to combine a blue LED with a yellow phosphor coating.

White light from LEDs made it possible to create energy-efficient lightbulbs for everyday use. It also made it possible to use the bulbs for providing a light source in liquid crystal display screens (a combination usually marketed as a ‘LED screen’), again saving energy.

The Nobel committee noted that a LED bulb can be nearly 19 times as efficient as a traditional lightbulb as well as lasting 100 times as long. It said that the technology could be “revolutionary” as around one-fourth of global electricity consumption is for lighting, and also noted that LED bulbs can be powered by solar panels, making electric lighting feasible for the 1.5 billion people who aren’t connected to a power grid.