Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect

Pieter Geiregat; Carmelita Rodá; Ivo Tanghe; Shalini Singh; Alessio Di Giacomo; Delphine Lebrun; Gianluca Grimaldi; Jorick Maes; Dries Van Thourhout; Iwan Moreels; Arjan J. Houtepen; Zeger Hens

doi:10.1038/s41377-021-00548-z

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Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect

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- Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect
- Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect
- LSA 2021年10卷第6期页码：1122-1132
- Affiliations：
  
  1.Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
  2.Center for Nano and Biophotonics, Ghent University, Gent, Belgium
  3.Photonics Research Group, Ghent University, Gent, Belgium
  4.Department of Chemical Sciences and Bernal Institute, University of Limerick, Limerick, Ireland
  5.Center for Nanophotonics, NWO-Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
  6.Opto-Electronic Materials Section, Department of Chemical Engineering, Delft University, Delft, The Netherlands
- Author bio：
  
  Pieter Geiregat (pieter.geiregat@ugent.be)
- Funds：
- DOI：10.1038/s41377-021-00548-z
  中图分类号：
- 纸质出版日期：2021-06-30，
  
  网络出版日期：2021-05-31，
  
  收稿日期：2021-01-19，
  
  修回日期：2021-04-21，
  
  录用日期：2021-04-28
- Accepted：
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Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect[J]. LSA, 2021,10(6):1122-1132.

Geiregat, P. et al. Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect. Light: Science & Applications, 10, 1122-1132 (2021).
Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect[J]. LSA, 2021,10(6):1122-1132. DOI： 10.1038/s41377-021-00548-z.

Geiregat, P. et al. Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect. Light: Science & Applications, 10, 1122-1132 (2021). DOI： 10.1038/s41377-021-00548-z.

摘要

Abstract

2D materials are considered for applications that require strong light-matter interaction because of the apparently giant oscillator strength of the exciton transitions in the absorbance spectrum. Nevertheless

the effective oscillator strengths of these transitions have been scarcely reported

nor is there a consistent interpretation of the obtained values. Here

we analyse th

e transition dipole moment and the ensuing oscillator strength of the exciton transition in 2D CdSe nanoplatelets by means of the optically induced Stark effect (OSE). Intriguingly

we find that the exciton absorption line reacts to a high intensity optical field as a transition with an oscillator strength

Stark

that is 50 times smaller than expected based on the linear absorption coefficient. We propose that the pronounced exciton absorption line should be seen as the sum of multiple

low oscillator strength transitions

rather than a single high oscillator strength one

a feat we assign to strong exciton center-of-mass localization. Within the quantum mechanical description of excitons

this 50-fold difference between both oscillator strengths corresponds to the ratio between the coherence area of the exciton's center of mass and the total area

which yields a coherence area of a mere 6.1 nm

. Since we find that the coherence area increases with reducing temperature

we conclude that thermal effects

related to lattice vibrations

contribute to exciton localization. In further support of this localization model

we show that

Stark

is independent of the nanoplatelet area

correctly predicts the radiative lifetime

and lines up for strongly confined quantum dot systems.

关键词

Keywords

references

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