The main charge carrier in the ionic crystal is polaron or conduction?

AbstractIn summary, the conversation discusses the formation of small polarons in a perfect crystal under UV light, specifically in rutile-TiO2. The percentage of free conduction band electrons that form polarons and how many of them remain as free electrons until recombination with holes depends on the intensity and wavelength of the UV light. Research shows that in rutile-TiO2, small electron polarons are the dominant form, while in anatase-TiO2, free-like electrons or large polarons are dominant. This information can be found in the referenced article.
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TL;DR Summary
Suppose I have a perfect crystal(e.g.TiO2-Rutile, band gap=3ev), under UV light, there should photoconductivity, according to the condensed matter theory, some of these excited conduction band electrons would form small polarons, I am wondering how many percent of the free conduction band electrons would form polarons, and how many of them would stay as free electrons until recombination with holes?
Suppose I have a perfect crystal(e.g.TiO2-Rutile, band gap=3ev), under UV light, there should photoconductivity, according to the condensed matter theory, some of these excited conduction band electrons would form small polarons, I am wondering how many percent of the free conduction band electrons would form polarons, and how many of them would stay as free electrons until recombination with holes?
 
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Welcome to PF.
The answer will depend on the intensity, and also the wavelength of the UV light.
 
  • #3
Upon reaching equilibrium, quantum mechanical calculations show that in rutile-TiO2 the dominant form is small electron polarons. In anatase-TiO2, the dominant form is free-like electrons (or large polarons).
See for example:
https://pubs.rsc.org/en/content/articlelanding/2014/cp/c4cp03981e
 

FAQ: The main charge carrier in the ionic crystal is polaron or conduction?

What is a polaron?

A polaron is a quasiparticle that is formed when a charged particle, such as an electron, interacts with the surrounding atoms in a crystal lattice. This interaction causes the charged particle to become surrounded by a localized distortion in the lattice, which effectively reduces its mass and allows it to move more easily through the crystal.

What is a conduction band?

The conduction band is the energy level in a crystal lattice where the electrons are free to move and conduct electricity. In ionic crystals, the conduction band is typically formed by the overlapping of partially filled energy levels from the cations and anions in the lattice.

How do polarons affect conduction in ionic crystals?

Polarons play a significant role in the conduction of electricity in ionic crystals. They are responsible for reducing the effective mass of the charged particles, making it easier for them to move through the crystal and contribute to the overall conductivity. Additionally, polarons can interact with each other and form larger structures, known as polaron bands, which can further enhance the conductivity of the crystal.

Are polarons the only charge carriers in ionic crystals?

No, polarons are not the only charge carriers in ionic crystals. In addition to polarons, there can also be other types of charge carriers, such as free electrons or holes, which are created when an electron is missing from a filled energy level. The relative contribution of each type of charge carrier depends on factors such as temperature, crystal structure, and impurities in the crystal.

Can polarons be observed directly?

Yes, polarons can be observed directly using various experimental techniques, such as electron paramagnetic resonance or infrared spectroscopy. These methods allow scientists to detect the presence and behavior of polarons in ionic crystals, providing valuable insights into their role in conduction and other properties of these materials.

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