How Does Voltage Affect LED Color Through Band Gap Adjustments?

  • #1
Janusz Bednarski
5
0
Homework Statement
How can one use a quantum well to change the colour of emitted light from an LED without changing the semiconductor material?
Relevant Equations
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Hi!

This question is translated so that's why it might sound a bit weird. I know that the answer should mention the band diagram of the LED, and I think that the answer is to introduce an electrical contact connected to a voltage source. Then when you increase the voltage, it should attract the electrons from the quantum well, and repel the holes from the other well, thus increasing the band gap and increasing the emitted light's energy (different colour). And vice versa for a negative voltage.

Am I correct?

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  • #2
I am no longer "cutting edge" for LEDs but I am unaware of practical examples of this technology. Does anyone have a real-life example of this idea?
 

Related to How Does Voltage Affect LED Color Through Band Gap Adjustments?

What is the relationship between voltage and LED color?

The color of an LED is primarily determined by the band gap of the semiconductor material, not directly by the voltage. However, applying different voltages can affect the efficiency and intensity of the emitted light, but not its fundamental color. The band gap determines the wavelength (and thus the color) of the emitted light when electrons recombine with holes.

How does the band gap of a semiconductor influence LED color?

The band gap of a semiconductor is the energy difference between the valence band and the conduction band. When electrons fall from the conduction band to the valence band, they release energy in the form of photons. The energy of these photons corresponds to a specific wavelength of light, which determines the color. A larger band gap results in the emission of higher-energy (shorter wavelength) light, such as blue or violet, while a smaller band gap results in lower-energy (longer wavelength) light, such as red or infrared.

Can changing the voltage alter the band gap of an LED?

No, changing the voltage applied to an LED does not alter the intrinsic band gap of the semiconductor material. The band gap is a fixed property of the material. What voltage can affect is the current flowing through the LED, which can influence the brightness and efficiency of the light emitted, but not the fundamental color.

Why do LEDs of different colors require different forward voltages?

LEDs of different colors are made from semiconductor materials with different band gaps. A higher band gap requires a higher forward voltage to overcome the potential barrier and allow current to flow. For example, blue LEDs typically have a higher forward voltage than red LEDs because the band gap of the material used for blue LEDs is larger, requiring more energy to excite electrons across the gap.

What happens if you exceed the recommended voltage for an LED?

Exceeding the recommended voltage for an LED can lead to excessive current flow, which can cause overheating and potentially damage the LED. This can result in reduced lifespan, decreased efficiency, or complete failure of the LED. It is crucial to use appropriate current-limiting resistors or constant current drivers to ensure the LED operates within its specified voltage and current ratings.

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