Exciton-exciton interaction and cascade relaxation of excitons in colloidal CdSe nanoplatelets

The exciton-exciton interaction and phonon-induced cascade relaxation of free electrons and holes determine the dynamic of stationary resonantly excited excitons in CdSe/CdS nanoplatelets. Along with saturation of the heavy-hole and light-hole exciton transitions explained by the phase space filling...

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Bibliographic Details
Published in:Journal of luminescence 2021-01, Vol.229, p.117682, Article 117682
Main Authors: Smirnov, Alexander M., Golinskaya, Anastasiya D., Saidzhonov, Bedil M., Vasiliev, Roman B., Mantsevich, Vladimir N., Dneprovskii, Vladimir S.
Format: Article
Language:English
Subjects:
Cascade relaxation
Exciton-exciton interaction
Nanoplatelets
Phase space filling
Phonon-exciton interaction
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Summary:The exciton-exciton interaction and phonon-induced cascade relaxation of free electrons and holes determine the dynamic of stationary resonantly excited excitons in CdSe/CdS nanoplatelets. Along with saturation of the heavy-hole and light-hole exciton transitions explained by the phase space filling effect the exciton-exciton interaction increases and starts to play a significant role in excitons dynamic. The lowest four band structure of CdSe/CdS nanoplatelets at the Γ point of Brillouin zone and its modification with CdS shell thickness changing are experimentally investigated for the first time. Bleaching of the two additional to the heavy- and light-hole exciton transitions with the energies higher than the absorbed photons energy can occur at room temperature due to rapid cascade relaxation of free electrons and holes formed as a result of the exciton-exciton interaction. To analyze the recombination and interaction of excitons in the colloidal nanoplatelets under high excitation densities the rate equations describing the exciton-exciton and exciton-electron interactions are applied. •The lowest four band structure of CdSe/CdS nanoplatelets are investigated.•The exciton-exciton interaction plays a significant role at high excitation densities.•High energy transitions bleaching occur due to cascade relaxation of free carriers.•Exciton transitions saturation are determined by phase space filling effect.•The exciton-exciton and exciton-electron interactions are analized by rate equations.
ISSN:0022-2313
1872-7883
DOI:10.1016/j.jlumin.2020.117682