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Size-dependent exciton substructure in CdSe nanoplatelets and its relation to photoluminescence dynamics

(2019) NANOSCALE. 11(25). p.12230-12241
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Abstract
CdSe nanoplatelets can be synthesized with different lateral sizes; very small nanoplatelets have almost quantum dot like features (almost discrete exciton states), while very large ones are expected to have properties of colloidal quantum wells (exciton continuum). However, nanoplatelets can be in an intermediate confinement regime with a rich substructure of excitons, which is neither quantum dot like nor an ideal 2D exciton. In this manuscript, we discuss the experimental transition energies and relaxation dynamics of exciton states in CdSe platelets with varying lateral dimensions and compare them with a microscopic theoretical model including exciton-phonon scattering. The model takes special care of the interplay of confinement and Coulomb coupling in the intermediate regime showing strong changes with respect to simple weak or strong confinement models by solving the full four dimensional lateral factorization free exciton wavefunction. Depending on the platelet size broad resonances previously attributed to just ground and excited states are actually composed of a rich substructure of several exciton states in their temporal dynamics. We show that these factorization free exciton states can explain the spectral features observed in photoluminescence experiments. Furthermore we demonstrate that the interplay of exciton bright and dark states provides principle insights into the overall temporal relaxation dynamics, and allows tuning of the exciton cooling via lateral platelet size. Our results and theoretical approach are directly relevant for understanding e.g. the size tuneability of lasing, excitonic cooling dynamics or light harvesting applications in these and similar 2D systems of finite lateral size.
Keywords
QUANTUM DOTS, COLLOIDAL NANOPLATELETS, RECOMBINATION DYNAMICS, ELECTRONIC-STRUCTURE, FINE-STRUCTURE, EMISSION, LOCALIZATION, SEMICONDUCTORS, NANOCRYSTALS, RELAXATION

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MLA
Specht, Judith F et al. “Size-dependent Exciton Substructure in CdSe Nanoplatelets and Its Relation to Photoluminescence Dynamics.” NANOSCALE 11.25 (2019): 12230–12241. Print.
APA
Specht, J. F., Scott, R., Corona Castro, M., Christodoulou, S., Bertrand, G. H., Prudnikau, A. V., Antanovich, A., et al. (2019). Size-dependent exciton substructure in CdSe nanoplatelets and its relation to photoluminescence dynamics. NANOSCALE, 11(25), 12230–12241.
Chicago author-date
Specht, Judith F, Riccardo Scott, Marta Corona Castro, Sotirios Christodoulou, Guillaume HV Bertrand, Anatol V Prudnikau, Artsiom Antanovich, et al. 2019. “Size-dependent Exciton Substructure in CdSe Nanoplatelets and Its Relation to Photoluminescence Dynamics.” Nanoscale 11 (25): 12230–12241.
Chicago author-date (all authors)
Specht, Judith F, Riccardo Scott, Marta Corona Castro, Sotirios Christodoulou, Guillaume HV Bertrand, Anatol V Prudnikau, Artsiom Antanovich, Laurens DA Siebbeles, Nina Owschimikow, Iwan Moreels, Mikhail Artemyev, Ulrike Woggon, Alexander W Achtstein, and Marten Richter. 2019. “Size-dependent Exciton Substructure in CdSe Nanoplatelets and Its Relation to Photoluminescence Dynamics.” Nanoscale 11 (25): 12230–12241.
Vancouver
1.
Specht JF, Scott R, Corona Castro M, Christodoulou S, Bertrand GH, Prudnikau AV, et al. Size-dependent exciton substructure in CdSe nanoplatelets and its relation to photoluminescence dynamics. NANOSCALE. 2019;11(25):12230–41.
IEEE
[1]
J. F. Specht et al., “Size-dependent exciton substructure in CdSe nanoplatelets and its relation to photoluminescence dynamics,” NANOSCALE, vol. 11, no. 25, pp. 12230–12241, 2019.
@article{8625786,
  abstract     = {CdSe nanoplatelets can be synthesized with different lateral sizes; very small nanoplatelets have almost quantum dot like features (almost discrete exciton states), while very large ones are expected to have properties of colloidal quantum wells (exciton continuum). However, nanoplatelets can be in an intermediate confinement regime with a rich substructure of excitons, which is neither quantum dot like nor an ideal 2D exciton. In this manuscript, we discuss the experimental transition energies and relaxation dynamics of exciton states in CdSe platelets with varying lateral dimensions and compare them with a microscopic theoretical model including exciton-phonon scattering. The model takes special care of the interplay of confinement and Coulomb coupling in the intermediate regime showing strong changes with respect to simple weak or strong confinement models by solving the full four dimensional lateral factorization free exciton wavefunction. Depending on the platelet size broad resonances previously attributed to just ground and excited states are actually composed of a rich substructure of several exciton states in their temporal dynamics. We show that these factorization free exciton states can explain the spectral features observed in photoluminescence experiments. Furthermore we demonstrate that the interplay of exciton bright and dark states provides principle insights into the overall temporal relaxation dynamics, and allows tuning of the exciton cooling via lateral platelet size. Our results and theoretical approach are directly relevant for understanding e.g. the size tuneability of lasing, excitonic cooling dynamics or light harvesting applications in these and similar 2D systems of finite lateral size.},
  author       = {Specht, Judith F and Scott, Riccardo and Corona Castro, Marta and Christodoulou, Sotirios and Bertrand, Guillaume HV and Prudnikau, Anatol V and Antanovich, Artsiom and Siebbeles, Laurens DA and Owschimikow, Nina and Moreels, Iwan and Artemyev, Mikhail and Woggon, Ulrike and Achtstein, Alexander W and Richter, Marten},
  issn         = {2040-3364},
  journal      = {NANOSCALE},
  keywords     = {QUANTUM DOTS,COLLOIDAL NANOPLATELETS,RECOMBINATION DYNAMICS,ELECTRONIC-STRUCTURE,FINE-STRUCTURE,EMISSION,LOCALIZATION,SEMICONDUCTORS,NANOCRYSTALS,RELAXATION},
  language     = {eng},
  number       = {25},
  pages        = {12230--12241},
  title        = {Size-dependent exciton substructure in CdSe nanoplatelets and its relation to photoluminescence dynamics},
  url          = {http://dx.doi.org/10.1039/c9nr03161h},
  volume       = {11},
  year         = {2019},
}

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