LED lights, or Light Emitting Diodes, are relative newcomers to the lighting scene, but their history stretches back farther than most assume. Although they’ve been used in commercial applications since the 1960s, they’re only now beginning to become a feasible option for residential use, which leads many to assume that light emitting diodes are a new technology. However, the first key discovery in their development was made in 1907, by a scientist named H. J. Round.
Round was working for Marconi Labs, a British telecommunications company, when he discovered the phenomenon of electroluminescence: the quality of some materials to produce light when an electric current was run through them. He was investigating the quality of a crystal to allow electric current to pass through in one direction while resisting it in another: a key feature of diodes, which function something like check valves for electrons. Round wrote up his discovery in the journal Electrical World, but it wasn’t until 1927 that a Russian scientist named Oleg Losev created into a functional light-emitting diode.
Losev was a radio technician, and in the course of his work he noticed the same phenomenon Round had documented: the diodes used in radio receivers glowed when transmitting current. Losev was interested in electrical generation of light; between 1924 and 1941 he documented his development of a device to generate electroluminescent light. Ten years later, in 1951, a Czech immigrant into America, took and refined Losev’s work with a team of other scientists. The scientific literature on light generation by electroluminescence grew steadily more robust.
In 1961, the year of John F. Kennedy’s inauguration and Yuri Gagarin’s historic orbit, a team of experimenters at Texas Instruments patented an infrared LED made from the compound gallium arsenide. The next year a scientist ad General Electric, Nick Holonyak, Jr., created another LED: a red in the visible spectrum. Holonyak is praised as the father of the LED, though his graduate student M. George Craford improved upon his work, discovering a way to emit yellow light as well as increasing the efficiency of red-spectrum LEDs by a factor of ten just a decade later.
Although this opened the door for commercial use of LEDs, market penetration was slow due to the expense of this new technology. Through the 1960s, visible LEDs could coast as much as $200 per unit, and found use mainly in indicator lamps and displays for electrical testing equipment. This barrier took a major blow with a discovery by Dr. Jean Hoerni, who invented a process of producing semiconductors – a key part of an LED’s operation – which allowed his company, Fairchild Semiconductor, to produce LEDs for only a few cents each.
And the science of LEDs continued to advance and more spectrums were unlocked, LEDs became more and more accessible for various applications. But it wasn’t until 1994 that Shuji Nakamura, a Japanese expatriate researching at the University of California, Santa Barbara, discovered a method to create a bright blue LED – and then took it one step further, applying a phosphorescent coating to the blue LED which caused it to produce a bright white light. With this discovery, LEDs became practical for illumination, and not just indication.
The history of the LED has spanned over a century, and remains a fertile area of research and development today. As LEDs become less expensive and more easily available, it’s not unreasonable to think that a lighting revolution will follow. Alread many retailers are phasing out sales of incandescent and even CFL lights in favor the more energy efficient LED lights.