Abstract
Colloidal CdSe nanocrystals (NCs) overcoated with an ultrathick CdS shell, also known as dot-in-bulk (DiB) structures, can support two types of excitons, one of which is core-localized and the other, shell-localized. In the case of weak "sub-single-exciton" pumping, emission alternates between the core-and shell-related channels, which leads to two-color light. This property makes these structures uniquely suited for a variety of photonic applications as well as ideal model systems for realizing complex excitonic quasi-particles that do not occur in conventional core/shell NCs. Here, we show that the DiB design can enable an unusual regime in which the same long-lived resident electron can endow trionlike characteristics to either of the two excitons of the DiB NC (core-or shell-based). These two spectrally distinct trion states are apparent in the measured photoluminescence (PL) and spin dynamics of core and shell excitons conducted over a wide range of temperatures and applied magnetic fields. Low-Temperature PL measurements indicate that core-and shell-based trions are characterized by a nearly ideal (â 100%) emission quantum yield, suggesting the strong suppression of Auger recombination for both types of excitations. Polarization-resolved PL experiments in magnetic fields of up to 60 T reveal that the core-and the shell-localized trions exhibit remarkably similar spin dynamics, which in both cases are controlled by spin-flip processes involving a heavy hole.
Original language | English |
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Journal | Nano letters |
DOIs | |
Publication status | Published - 2019 |
Keywords
- Nanocrystals
- charged excitons/trions
- core/shell heterostructures
- dual emission
- spin dynamics
ASJC Scopus subject areas
- Bioengineering
- Chemistry(all)
- Materials Science(all)
- Condensed Matter Physics
- Mechanical Engineering