LEDs different colours and their forward(working) voltage

In summary, the conversation revolves around understanding the reason for the different forward voltages of red, green, and white LEDs. The demonstrator did not explain it in the lab, but the person wants to know the reason behind it. Upon researching, it is discovered that the energy of the emitted photon depends on the bandgap of the material, which is different for red, green, and blue LEDs. It is also mentioned that white LEDs consist of blue LEDs with a phosphor that emits white light.
  • #1
indie452
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Homework Statement


hi I've just been doing labs today on data aquisition looking at current voltage characteristics, one thing that i did was look at the forward(working) voltage for a red, green and white LED.

Red = 1.5V Green = 1.8V White = 2.6V

when i asked the demonstarter why this was he said that we arent asked to know this to write in our lab books and so it didnt matter, but i do want to know why.

ive looked on the web and i think it has something to do with the wavelength produced and that each one might need slightly more energy to get the lower wavelength [cause E=hc/[tex]\lambda[/tex]] and white light needs a lot more at it isn't monochromatic.

is any of this thinking right?
 
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  • #2
Roughly correct.
The energy of the photon emitted depends on the bandgap of the material as does the forward voltage.
Red, green and blue LEDs use different semiconductor material (or simialir material with different doping) with different bandgaps.
To slightly confuse things white LEDs are generally blue LEDs with a phosphor that is excited by high energy blue light and emits roughly white light
 

FAQ: LEDs different colours and their forward(working) voltage

1. What are the different colors available for LEDs?

There are many colors available for LEDs, including red, green, blue, yellow, amber, purple, and white. Each color is created by using a different semiconductor material in the LED's construction.

2. How does the forward voltage affect the color of an LED?

The forward voltage is the voltage required for an LED to emit light. The color of an LED is determined by the bandgap energy of the semiconductor material used. Different colors require different amounts of energy, which results in different forward voltages.

3. Can an LED emit more than one color?

Yes, it is possible for an LED to emit multiple colors. This is achieved by using a process called color mixing, where multiple colored LEDs are combined to create a desired color. However, each LED will still have its own specific forward voltage.

4. Why does the forward voltage vary for different colors of LEDs?

The forward voltage varies for different colors of LEDs because each color requires a different bandgap energy. This energy is determined by the semiconductor material used, and the different materials have different properties that affect the forward voltage.

5. Can the forward voltage of an LED be changed?

No, the forward voltage of an LED is determined by the materials and construction of the LED and cannot be changed. However, the brightness of an LED can be adjusted by changing the current flowing through it.

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