It’s fifty years ago this week since the first practical experiment producing visible light from a light-emitting diode.
The idea that electricity could directly generate light goes back to the early 20th century. That led to exploration of the idea of tweaking the principle of a transistor to intentionally control the movement of electrons and cause them to release energy in the form of photons.
The first step was to carry out this process to produce infrared light: several people claimed the credit for this over the years, with the first patent awarded in 1961 to Robert Biard and Gary Pittman of Texas Instruments.
A year later Nick Holonyak of General Electric developed the technique further to produce a visible yellow light. He told the BBC that at the time a LED would cost $262 to make, which is just under $2,000 at today’s prices. His findings were first published in December 1962 in the Applied Physics Letters journal.
Holonyak noted that it took more time to figure out how to produce the higher wavelengths that produced different colors. Red came next which is why it most commonly appears on digital displays on older devices such as calculators.
The main benefits of LEDs are efficiency, instant reaction and durability. Holonyak notes that unlike many forms of electronic lighting, a LED directly converts electricity to light without needing an intermediate stage such as heat. He explains that LEDs work as close to 100 percent efficiency as possible.
Holonyak also tells the BBC that a car brake light using LEDs shows both of the other two advantages. To the human eye, the LEDs switch on instantaneously, giving the driver behind the quickest possible warning, while the light should outlast the car itself. One drawback is that performance decreases at higher temperatures.
By coincidence, Ikea announced just last week that it will switch to selling LED lights only from 2016. The retailer had already ditched incandescent bulbs from 2011. Ikea says this will “drive market acceptance in a good way”, the logic appearing to be that if people don’t see any other types of bulbs on the shelves, they might buy LED rather than make a trip to another store. And who among us can say they’ve walked out of Ikea with an appetite for further shopping that day…
(Image credit: Afrank99 via Creative Commons license)