Related Experiment Video
Updated: Jul 8, 2025

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Negative diffusion of excitons in quasi-two-dimensional systems
Aleksandr A Kurilovich1, Vladimir N Mantsevich2, Aleksei V Chechkin3,4,5
1Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, 121205, Moscow, Russia.
Abstract:
We show how two different mobile-immobile type models explain the observation of negative diffusion of excitons reported in experimental studies in quasi-two-dimensional semiconductor systems. The main reason for the effect is the initial trapping and a delayed release of free excitons in the area close to the original excitation spot. The density of trapped excitons is not registered experimentally. Hence, the signal from the free excitons alone includes the delayed release of not diffusing trapped particles. This is seen as the narrowing of the exciton density profile or decrease of mean-squared displacement which is then interpreted as a negative diffusion. The effect is enhanced with the increase of recombination intensity as well as the rate of the exciton-exciton binary interactions.
Related Concept Videos
Carrier Transport
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
P-N junction
Diffusion
Types of Semiconductors
Protein Diffusion in the Membrane
Electric Field of Two Equal and Opposite Charges
A separation of the positive and negative charges can lead to a weak, remnant effect of the positive and negative charges. The expectation is that the more the distance between the positive and...

