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Issue 7, 2014
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Influence of the core size on biexciton quantum yield of giant CdSe/CdS nanocrystals

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Abstract

We present a systematic study of photoluminescence (PL) emission intensity and biexciton (BX) quantum yields (QYBX) in individual “giant” CdSe/CdS nanocrystals (g-NCs) as a function of g-NC core size and shell thickness. We show that g-NC core size significantly affects QYBX and can be utilized as an effective tuning parameter towards higher QYBX while keeping the total volume of the g-NC constant. Specifically, we observe that small-core (2.2 nm diameter) CdSe/CdS NCs with a volume of ∼200 nm3 (shell comprises 4 CdS monolayers) show very low average and maximum QYBX's of ∼3 and 7%, respectively. In contrast, same-volume medium-core (3 nm diameter) NCs afford higher average values of ∼10%, while QYBX's of ∼30% are achieved for same-volume large-core (5.5 nm diameter) CdSe/CdS NCs, with some approaching ∼80%. These observations underline the influence of the g-NC core size on the evolution of PL emissive states in multi-shell NCs. Moreover, our study also reveals that the use of long anneal times in the growth of CdS shells plays a critical role in achieving high QYBX.

Graphical abstract: Influence of the core size on biexciton quantum yield of giant CdSe/CdS nanocrystals

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Article information


Submitted
10 Dec 2013
Accepted
04 Feb 2014
First published
06 Feb 2014

Nanoscale, 2014,6, 3712-3720
Article type
Paper

Influence of the core size on biexciton quantum yield of giant CdSe/CdS nanocrystals

B. D. Mangum, S. Sampat, Y. Ghosh, J. A. Hollingsworth, H. Htoon and A. V. Malko, Nanoscale, 2014, 6, 3712 DOI: 10.1039/C3NR06558H

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