Two-color emitting colloidal semiconductor nanocrystals (NCs) are of interest for applications in multimodal imaging, sensing, lighting, and integrated photonics. Dual color emission from core- and shell-related optical transitions has been recently obtained using so-called dot-in-bulk (DiB) CdSe/CdS NCs comprising a quantum-confined CdSe core embedded into an ultrathick (∼7-9 nm) CdS shell. The physical mechanism underlying this behavior is still under debate. While a large shell volume appears to be a necessary condition for dual emission, comparison between various types of thick-shell CdSe/CdS NCs indicates a critical role of the interface "sharpness" and the presence of potential barriers. To elucidate the effect of the interface morphology on the dual emission, we perform side-by-side studies of CdSe/CdS DiB-NCs with nominally identical core and shell dimensions but different structural properties of the core/shell interface arising from the crystal structure of the starting CdSe cores (zincblende vs wurtzite). While both structures exhibit dual emission under comparable pump intensities, NCs with a zincblende core show a faster growth of shell luminescence with excitation fluence and a more readily realized regime of amplified spontaneous emission (ASE) even under "slow" nanosecond excitation. These distinctions can be linked to the structure of the core/shell interface: NCs grown from the zincblende cores contain a ∼3.5 nm thick zincblende CdS interlayer, which separates the core from the wurtzite CdS shell and creates a potential barrier for photoexcited shell holes inhibiting their relaxation into the core. This helps maintain a higher population of shell states and simplifies the realization of dual emission and ASE involving shell-based optical transitions.

Pinchetti, V., Meinardi, F., Camellini, A., Sirigu, G., Christodoulou, S., Bae, W., et al. (2016). Effect of Core/Shell Interface on Carrier Dynamics and Optical Gain Properties of Dual-Color Emitting CdSe/CdS Nanocrystals. ACS NANO, 10(7), 6877-6887 [10.1021/acsnano.6b02635].

Effect of Core/Shell Interface on Carrier Dynamics and Optical Gain Properties of Dual-Color Emitting CdSe/CdS Nanocrystals

PINCHETTI, VALERIO
Primo
;
MEINARDI, FRANCESCO
Secondo
;
BROVELLI, SERGIO
Ultimo
2016

Abstract

Two-color emitting colloidal semiconductor nanocrystals (NCs) are of interest for applications in multimodal imaging, sensing, lighting, and integrated photonics. Dual color emission from core- and shell-related optical transitions has been recently obtained using so-called dot-in-bulk (DiB) CdSe/CdS NCs comprising a quantum-confined CdSe core embedded into an ultrathick (∼7-9 nm) CdS shell. The physical mechanism underlying this behavior is still under debate. While a large shell volume appears to be a necessary condition for dual emission, comparison between various types of thick-shell CdSe/CdS NCs indicates a critical role of the interface "sharpness" and the presence of potential barriers. To elucidate the effect of the interface morphology on the dual emission, we perform side-by-side studies of CdSe/CdS DiB-NCs with nominally identical core and shell dimensions but different structural properties of the core/shell interface arising from the crystal structure of the starting CdSe cores (zincblende vs wurtzite). While both structures exhibit dual emission under comparable pump intensities, NCs with a zincblende core show a faster growth of shell luminescence with excitation fluence and a more readily realized regime of amplified spontaneous emission (ASE) even under "slow" nanosecond excitation. These distinctions can be linked to the structure of the core/shell interface: NCs grown from the zincblende cores contain a ∼3.5 nm thick zincblende CdS interlayer, which separates the core from the wurtzite CdS shell and creates a potential barrier for photoexcited shell holes inhibiting their relaxation into the core. This helps maintain a higher population of shell states and simplifies the realization of dual emission and ASE involving shell-based optical transitions.
Articolo in rivista - Articolo scientifico
amplified spontaneous emission; core/shell heterostructures; dual emission; exciton dynamics; interface structure; nanocrystal quantum dots;
amplified spontaneous emission; core/shell heterostructures; dual emission; exciton dynamics; interface structure; nanocrystal quantum dots; Engineering (all); Materials Science (all); Physics and Astronomy (all)
English
2016
10
7
6877
6887
none
Pinchetti, V., Meinardi, F., Camellini, A., Sirigu, G., Christodoulou, S., Bae, W., et al. (2016). Effect of Core/Shell Interface on Carrier Dynamics and Optical Gain Properties of Dual-Color Emitting CdSe/CdS Nanocrystals. ACS NANO, 10(7), 6877-6887 [10.1021/acsnano.6b02635].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/130655
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