Temperature Dependence of Excitonic and Biexcitonic Decay Rates in Single Colloidal Nanoplatelets

Elad Benjamin^a, Venkata Jayasurya Yallapragada^a^,^b, Dan Oron^a

^aDepartment of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel

^bDepartment of Physics, Indian Institute of Kanpur, Kanpur 208016, India

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Spring Meeting 2022 (NSM22)

#SNI22. Semiconductor Nanocrystals I: Basic Science (synthesis, spectroscopy, electronic structure, device and application)

Online, Spain, 2022 March 7th - 11th

Organizers: Emmanuel Lhuillier, Sandrine Ithurria and Angshuman Nag

Contributed talk, Elad Benjamin, presentation 009
DOI: https://doi.org/10.29363/nanoge.nsm.2022.009
Publication date: 7th February 2022

Excitons in colloidal semiconductor nanoplatelets (NPLs) are weakly confined in the lateral dimensions, resulting in significantly smaller Auger rates. Thus, when compared to spherical quantum dots (QDs) NPLs display much graeter biexciton quantum yields. Recent work by Li et al. [2] further suggests the recombination dynamics in NPLs differ significantly from QDs. Rather it follows that of semiconductor quantum wells (QW).

Here we report a study of the temperature dependence of the biexciton Auger rate in individual CdSe/CdS core−shell NPLs, through the measurement of time-gated second-order photon correlations in the photoluminescence [1]. This is property is fundementally different between QDs and QWs, and studying single particles we eliminate ensemble inhomogenety as well as charging and photobleaching effecting common ensemble methods for measuring Auger rates. We also utilize this method to directly estimate the single-exciton radiative rate. We find that whereas the radiative lifetime of NPLs increases with temperature, the Auger lifetime is almost temperature-independent. These behaviour is qualitatively similar to that of QWs. Time-gated photon correlation measurements offer the unique ability to study multiphoton emission events, while excluding effects of competing fast processes, and can provide significant insight into the photophysics of a variety of nanocrystal multiphoton emitters.

References:

[1] Benjamin, E.; Yallapragada, V. J.; Amgar, D.; Yang, G.; Tenne, R.; Oron, D. Temperature dependence of excitonic and biexcitonic decay rates in colloidal nanoplatelets by time-gated photon correlation. J. Phys. Chem. Lett. 2020, 11(16), 6513-6518.

[2] Li, Q.; Lian, T. Area- and Thickness-Dependent Biexciton Auger Recombination in Colloidal CdSe Nanoplatelets: Breaking the “Universal Volume Scaling Law. Nano Lett. 2017, 17, 3152−3158.

Acknowledgements:

All particle synthesis and TEM analysis was done by Daniel Amgar and Gaoling Yang. This work was supported by ERC Consolidator grant ColloQuantO and by the Crown Center of Photonics.

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