Dual-Emitting Dot-in-Bulk CdSe/CdS Nanocrystals with Highly Emissive Core- and Shell-Based Trions Sharing the Same Resident Electron
journal contributionposted on 2019-11-07, 19:07 authored by Valerio Pinchetti, Elena V. Shornikova, Gang Qiang, Wan Ki Bae, Francesco Meinardi, Scott A. Crooker, Dmitri R. Yakovlev, Manfred Bayer, Victor I. Klimov, Sergio Brovelli
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 (∼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.
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Shell-Based Trions60 TSame Resident Electron Colloidal CdSe nanocrystalsshell-based trionsLow-temperature PL measurementsshell-related channelsresident electronphotonic applicationscorespin-flip processesDiB NCtrion statesultrathick CdS shelltrionlike characteristicsDiB designshell-localized trions exhibitshell excitonsmodel systemsAuger recombinationexcitonic quasi-particlesPolarization-resolved PL experimentsEmissive Core