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Hétérostructures, dopage et chimie de surface : contrôle de la structure et des propriétés optiques de nanoplaquettes de chalcogénures de cadmium

Abstract : Cadmium chalcogenide nanoplatelets present unique optical properties resulting from their atomically precise thickness control. They have emerged as a new promising class of nanomaterial for optoelectronic applications. The goal of this thesis is to promote new optical properties through the design and surface chemistry of nanoplatelets. Firstly, CdSe/CdSe1-xTex core/crown heterostructures were synthesized and showed bicolor emission at the scale of a single nanoplatelet. This bicolor emission results from a competition between the localization of the electron in the CdSe core driven by the conduction band offset and the direct exciton recombination in the crown favored by the high exciton binding energy. Silver doped nanoplatelets were synthesized in the second part. This doping, performed through partial cation exchange, creates a silver-related emissive state in the band gap. The amount of silver incorporated in the nanoplatelet allows a progressive control of the emission color from green to red thanks to the coexistence of the band edge and the silver related emission. The silver state is strongly bound and is located 340 meV above the bulk valence band. Finally, the modification of the surface chemistry with bromide and oleylamine reduces the surface stresses and improves the surface passivation. This leads to a shift, beyond the discrete confinement, of the emission wavelength and increases the quantum yield up to 75 %.
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  • HAL Id : tel-02926283, version 1

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Marion Dufour. Hétérostructures, dopage et chimie de surface : contrôle de la structure et des propriétés optiques de nanoplaquettes de chalcogénures de cadmium. Science des matériaux [cond-mat.mtrl-sci]. Sorbonne Université, 2019. Français. ⟨NNT : 2019SORUS487⟩. ⟨tel-02926283⟩

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