What is Wannier exciton?

When an exciton’s radius extends over several unit cells, it is referred to as a Wannier exciton in contrast to Frenkel excitons whose size is comparable with the unit cell. An excited solid typically contains many electrons and holes; this modifies the Wannier equation considerably.

What is bound exciton?

bound exciton is usually an e-h pair bound to a defect such as a lattice atom vacancy, this offers additional coulomb energy to make the bound exciton energy lower than that of the free neutral exciton, giving redshifted PL peak and broadened peak width.

Where can I find exciton binding energy?

Abstract: For small organic conjugated molecules the exciton binding energy can be calculated treating molecules as conductor, and is given by a simple relation BE ≈ e2/(4πε0εR), where ε is the dielectric constant and R is the equivalent radius of the molecule.

What is excitonic resonance?

The excitonic states are computed taking into account both the renormalization of the electron–hole interaction and self-energy effects induced by the metallic segment on the electron–hole pair, as well as by the dielectric environment, through an induced charge numerical approach.

What is exciton in semiconductor?

Excitons are quasi-particles that form when Coulomb-interacting electrons and holes in semiconductors are bound into pair states. They have many features analogous to those of atomic hydrogen. Excitonic signatures commonly appear in the optical absorption and emission of direct-gap semiconductor systems.

What are exciton give its types?

This is termed as exciton. In organic materials two models are used: the band or wave model (low temperature, high crystalline order) and the hopping model (higher temperature, low crystalline order or amorphous state). Energy transfer in the hopping limit is identical with energy migration.

What is the meaning of exciton?

An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids.

What is exciton binding energy of ZnO?

Zinc oxide (ZnO) is an extremely versatile n-type semiconductor material with a large exciton binding energy of 60 meV and a large band-gap energy of 3.37 eV at room temperature (259,260).

What is exciton binding energy in GaAs?

Abstract. The exciton energy spectrum in GaAs has been studied by photoluminescence and reflection. The value for the exciton binding energy was determined to be (4.20 ± 0.3) × 10−3 eV from which the band-gap energy of 1.5195 ± 0.0005 eV has been deduced.

What is self trapped exciton?

Self-trapped excitons (STEs), occurring in a material with soft lattice and strong electron–phonon coupling, emit photons with broad spectrum and large Stokes shift. Recently, series halide perovskites with efficient STE emission have been reported and showed promise for solid-state lighting.

What is exciton used for?

Excitons are the main mechanism for light emission in semiconductors at low temperature (when the characteristic thermal energy kT is less than the exciton binding energy), replacing the free electron-hole recombination at higher temperatures.

What is charge of exciton?

Related Content. Related Topics: Quasiparticle Wannier exciton Electron-hole pair. See all facts and data → Because the electron and the positive hole have equal but opposite electrical charges, the exciton as a whole has no net electrical charge (though it transports energy).

What is the binding energy of a defect bound exciton?

Our results indicate low-temperature binding energies of 13 meV (29 meV) for the free (defect-bound) exciton, with the 16 meV localization energy for excitons attributed to binding to point defects. Our findings shed light on the wide range of binding energies (2–55 meV) reported in recent years.

How are bound exciton and donor recombinations identified?

Annealing annihilates this shallow donor which has a bound exciton recombination at 3.3628 eV. Correlated by magnetic resonance experiments we attribute this particular donor to hydrogen. The Al, Ga and In donor bound exciton recombinations are identified based on doping and diffusion experiments and using secondary ion mass spectroscopy.

What happens when an exciton binds to a biexciton?

Provided the interaction is attractive, an exciton can bind with other excitons to form a biexciton, analogous to a dihydrogen molecule. If a large density of excitons is created in a material, they can interact with one another to form an electron-hole liquid, a state observed in k-space indirect semiconductors.

What is the binding energy of a donor exciton?

Two electron satellite transitions (TES) of the donor bound excitons allow to determine the donor binding energies ranging from 46 to 73 meV. These results are in line with the temperature dependent Hall effect measurements.