How do light dependent resistors work with photons and electrons?

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SUMMARY

A light dependent resistor (LDR), also known as a photoresistor, operates by utilizing photons to excite electrons in semiconductor materials, primarily silicon. When a photon possesses sufficient energy, it elevates an electron into the conduction band, allowing it to move freely and generate an electric current. Increased light exposure results in a higher number of free electrons, leading to lower resistance and increased current flow. Cadmium sulfide (CdS) is the common material used in the construction of LDRs.

PREREQUISITES
  • Understanding of semiconductor physics
  • Knowledge of photon energy and electron excitation
  • Familiarity with electrical resistance concepts
  • Basic principles of current flow in materials
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  • Research the properties of cadmium sulfide (CdS) in electronic applications
  • Learn about the conduction band and valence band in semiconductors
  • Explore the relationship between light intensity and resistance in LDRs
  • Investigate alternative materials used for photoresistors
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Electronics enthusiasts, physics students, and engineers interested in photonic applications and semiconductor technology will benefit from this discussion.

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How does a light dependent resistor (photoresistor) work in terms of photons and electrons?

Thanks,
Jamie
 
Science news on Phys.org
In an intrinsic semiconductor material like silicon, the electrons are held onto the atom strongly enough that the material is normally an insulator.
A photon with enough energy can excite an electron up into the conduction band where it is more free of the atom and can move through the material carrying a current.
The more light, the more free electrosn, the more current and th elower the resistance.
 
mgb_phys has given a good description of the physics behind light dependent resistors. FYI, they are typically made from cadmium sulfide (CdS).
 

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