Why did blue LEDs win a Nobel Prize when red ones were everywhere? Because an LED's color is locked to its material's band gap — and blue needed a whole new one.
LED Band Gap & ColorLive
from energy gap to photon
590 nm
2.10 eV band gap
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An LED emits light when electrons drop across the semiconductor's band gap, each releasing a photon of energy equal to that gap. Since photon energy fixes wavelength (λ = 1240/Eg in nm), the band gap directly sets the color — which is why blue LEDs needed a whole new material (gallium nitride) and a Nobel Prize to achieve.
Reading this result: λ = 1240/Eg puts this 2.10 eV gap at 590 nm — a wider gap means a bluer photon, which is exactly why blue LEDs needed the high-gap GaN family.
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How it works
An LED emits a photon each time an electron crosses the semiconductor band gap, with energy exactly equal to that gap. Since a photon's energy fixes its wavelength (λ ≈ 1240/Eg nanometers), the band gap directly determines the color. Wider gaps give blue and ultraviolet, narrower ones red and infrared — and achieving efficient blue with gallium nitride revolutionized lighting.
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