Addressing the exciton fine structure in colloidal nanocrystals: the case of CdSe nanoplatelets

Abstract

We study the band-edge exciton fine structure and in particular its bright-dark splitting in colloidal semiconductor nanocrystals by four different optical methods based on fluorescence line narrowing and time-resolved measurements at various temperatures down to 2 K. We demonstrate that all these methods provide consistent splitting values and discuss their advances and limitations. Colloidal CdSe nanoplatelets with thicknesses of 3, 4 and 5 monolayers are chosen for experimental demonstrations. The bright-dark splitting of excitons varies from 3.2 to 6.0 meV and is inversely proportional to the nanoplatelet thickness. Good agreement between experimental and theoretically calculated size dependence of the bright-dark exciton slitting is achieved. The recombination rates of the bright and dark excitons and the bright to dark relaxation rate are measured by time-resolved techniques.

References in corpus (8)

• Ultra-thin PbS sheets by two-dimensional oriented attachment
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Cited by in corpus (13)

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• Surface spin magnetism controls the polarized exciton emission from CdSe nanoplatelets
• Complex diffusion-based kinetics of photoluminescence in semiconductor nanoplatelets
• Single and double electron spin-flip Raman scattering in CdSe colloidal nanoplatelets
• Magneto-optics of excitons interacting with magnetic ions in CdSe/CdMnS colloidal nanoplatelets
• Colloidal two-dimensional metal chalcogenides: Realization and application of the structural anisotropy
• Dielectric Confinement Enables Molecular Coupling in Stacked Colloidal Nanoplatelets
• Optical and electronic properties of colloidal CdSe Quantum Rings
• Negative diffusion of excitons in quasi-two-dimensional systems
• Theory of single and double electron spin-flip Raman scattering in semiconductor nanoplatelets
• Bright-Dark Exciton Interplay Evidenced by Spin Polarization in CdSe/CdMnS Nanoplatelets