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Main Title: Size-dependent exciton substructure in CdSe nanoplatelets and its relation to photoluminescence dynamics
Author(s): Specht, Judith F.
Scott, Riccardo
Castro, Marta Corona
Christodoulou, Sotirios
Bertrand, Guillaume H. V.
Prudnikau, Anatol V.
Antanovich, Artsiom
Siebbeles, Laurens D. A.
Owschimikow, Nina
Moreels, Iwan
Artemyev, Mikhail
Woggon, Ulrike
Achtstein, Alexander W.
Richter, Marten
Type: Article
Language Code: en
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.
Issue Date: 12-Jun-2019
Date Available: 9-Jul-2019
DDC Class: 600 Technik, Technologie
Subject(s): nanoplatelets
exciton dynamics
Cadmium selenide
Sponsor/Funder: DFG, 182087777, SFB 951: Hybrid Inorganic/Organic Systems (HIOS) for Opto-Electronics
DFG, 265219982, Elektronischer Transport in kolloidalen II-VI Nanoplatelets und Nanorods
DFG, 324765876, Kontrolle der Relaxationsdynamik und Exziton-Phonon Wechselwirkung in extrem anisotropen Halbleitern: Das Modellsystem CdSe und II-VI Nanoplättchen
DFG, 235473865, Zwei-dimensionale CdSe Nanoplatelets mit magischen Schichtdicken
ERC/H2020/714876/EU/Photonics in Flatland: Band Structure Engineering of 2D Excitons in Fluorescent Colloidal Nanomaterials/PHOCONA
TU Berlin, Open-Access-Mittel - 2019
Journal Title: Nanoscale
Publisher: Royal Society of Chemistry
Publisher Place: Cambridge
Volume: 11
Publisher DOI: 10.1039/C9NR03161H
Page Start: 12230
Page End: 12241
EISSN: 2040-3372
Appears in Collections:FG Nichtlineare Optik » Publications

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