L.E.D's and the photoelctric effect

  • Thread starter ryan750
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In summary, the conversation discusses the principles of how L.E.D's (light-emitting diodes) work and how light from an ordinary filament lamp can cause a voltage to be produced in an L.E.D. It is explained that the photoelectric effect plays a role in this process, as the light from the lamp causes valence electrons to be released into the conduction/depletion layer of the semiconductor in the L.E.D. This creates a flow of current from the n-type to the p-type semiconductor, resulting in a voltage. It is noted that the material in the L.E.D would need to have a low work function or other specific properties for this process to occur. The conversation also invites corrections or additional information on the topic.
  • #1
hello - i feel confident that i understand the principles of how L.E.D's work. I can grasp the concept of the depletion zone and how this leads to conduction in one direction.

But how does light from an ordinary filament lamp cause a voltage in an L.E.D to be produced when the L.E.D has no obvious power supply?

I know of the principles of the photoelectric effect and realize it has something to do with this but need a concise explanation of how the voltage is produced.

i have been discussing this with sum1 else and have come up with this explanation:

light from the lamp when incident on the semiconductor in the L.E.D causes valence electrons in the n type semiconductor to be released into the conduction/ depletion layer. these are attracted to the p type semiconductor and they move into the 'holes'. this causes a drop in energy level for the electron which is called relaxation and causes light to be emitted.
this process means that a current is flowing from the n to the p type semiconductor which means that a voltage is present in this mini - circuit.

now the fact that white light has a low photon energy means that if it were the photoelectric efect that causes this process - the material in the L.E.D would need to have a low work function or sum other proerty that allows this to happen.

anyone who can correct any details - add more information - or completely change the explanation to the question - please feel free

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  • #3
for the explanation! You are correct in your understanding of the photoelectric effect and how it relates to the production of voltage in an L.E.D. The key factor here is the band gap energy of the semiconductor material used in the L.E.D. This band gap energy is the minimum amount of energy required for an electron to move from the valence band to the conduction band.

When light from the filament lamp hits the semiconductor material, it provides enough energy for some of the electrons in the valence band to jump to the conduction band. This creates a flow of electrons from the n-type to the p-type layer, resulting in a voltage difference. This voltage difference is what powers the L.E.D.

The reason why white light, which has a lower photon energy, can still produce this effect is because the semiconductor material used in L.E.D.s is specifically chosen to have a low band gap energy. This allows the electrons to easily jump to the conduction band with the energy provided by the light.

I hope this helps clarify the process of how L.E.D.s use the photoelectric effect to produce light and power. Let me know if you have any further questions or need more clarification.

1. What is the photoelectric effect?

The photoelectric effect is a phenomenon where electrons are emitted from a metal surface when it is exposed to light of a certain wavelength. This was first observed by Heinrich Hertz in 1887 and later explained by Albert Einstein in 1905.

2. How do LEDs work?

LEDs, or light-emitting diodes, work by converting electrical energy into light energy through a process called electroluminescence. When a current is passed through the LED's semiconductor material, it releases energy in the form of photons, producing light.

3. What is the difference between LED and traditional light bulbs?

LEDs are more energy-efficient than traditional light bulbs because they do not use a filament that can burn out. They also have a longer lifespan and do not emit heat, making them safer to use. However, they can be more expensive upfront.

4. Can LEDs produce different colors of light?

Yes, LEDs can produce different colors of light by using different materials for the semiconductor. For example, red LEDs use aluminum gallium arsenide (AlGaAs) while blue LEDs use indium gallium nitride (InGaN). By combining these materials, LEDs can produce a wide range of colors.

5. Are LEDs harmful to the environment?

LEDs are generally considered to be more environmentally friendly than traditional light bulbs because they use less energy and do not contain harmful substances like mercury. However, improper disposal of LEDs can still have a negative impact on the environment, so it is important to recycle them properly.

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