If we look back at the development of the LED is it surprising when the various elements came together and when the first LED effects were noticed.

Today we all use LEDs for a multitude of things: LED lamps for electronic equipment, LED alphanumeric displays, backlighting in TVs and of course LED lighting.

LEDs, the indicator lamps were announced in 1962 in the UK and also in the USA. This work built on the foundations of semiconductor technology: transistor developed in later 1940s, the FET later, etc.

But all of this work built on previous technology developments of diodes used in the 1940s for radars and before that theoretical particle physics of the 1920s and 1930s.

However a little known Russian engineer named Oleg Vladimirovich Losov did a lot of work looking at the characteristics of the light emitting effect, plotting IV curves, looking at spectra and publishing some of his results. However most of his work was lost in the Second World War in the Nazi seige of Leningrad.

However this was not the first observation of the light emitting diode effect. A British engineer named henry Round, H J Round did a lot of work on radio technology of the day and noticed the effect when he was looking at crystal detectors. A later version is seen on this 1crystal set radio from about 1923.

Writing in 1907 to a British journal named Electrical World he noted:

  Sirs:- During an investigation of the unsymmetrical passage of current through a contact of carborundum and other substances a curious phenomenon was noted. On applying a potential of 10 volts between two points on a crystal of carborundum, the crystal gave out a yellowish light. Only one or two specimens could be found which gave a bright glow on such a low voltage, but with 11 volts a large number could be found to glow. In some crystals only the edges gave the light and others gave instead a yellow light, green orange or blue. In all cases tested the glow appears to come from the negative pole, a bright blue-green spark appearing at the positive pole.

And he concluded:

The writer would be glad of references to any published account of an investigation of this or any allied phenomena.
H. J. Round

So this was probably the first account of the Light Emitting Diode, LED effect.

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History of the LED:
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H J Round:
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LED technology
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