Abstract
We demonstrate that a simple silver coated ball lens can be used to accurately measure the entire distribution of radiative transition rates of quantum dot nanocrystals. This simple and cost-effective implementation of Drexhage's method that uses nanometer-controlled optical mode density variations near a mirror, not only allows an extraction of calibrated ensemble-averaged rates, but for the first time also to quantify the full inhomogeneous dispersion of radiative and non radiative decay rates across thousands of nanocrystals. We apply the technique to novel ultrastable CdSe/CdS dot-in-rod emitters. The emitters are of large current interest due to their improved stability and reduced blinking. We retrieve a room-temperature ensemble average quantum efficiency of 0.87 +/- 0.08 at a mean lifetime around 20 ns. We confirm a log-normal distribution of decay rates as often assumed in literature, and we show that the rate distribution-width, that amounts to about 30% of the mean decay rate, is strongly dependent on the local density of optical states.
Original language | English |
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Pages (from-to) | 5984-5992 |
Number of pages | 9 |
Journal | ACS Nano |
Volume | 7 |
Issue number | 7 |
DOIs | |
Publication status | Published - Jul 2013 |
Funding
We are grateful to M. Frimmer and A. Mohtashami for help in the initial stages of the project. This work is part of the research program of the "Foundation for Fundamental Research on Matter (FOM), which is financially supported by the "The Netherlands Organization for Scientific Research (NWO)". A.F.K. gratefully acknowledges a NWO-Vidi grant for financial support. P.L. acknowledges support by the Carlsberg Foundation as well as the Danish Research Council for Independent Research (Grant No. FTP 11-116740).
Keywords
- quantum dots
- nanorods
- quantum rods
- quantum efficiency
- Drexhage
- optical density of states
- decay-rate distribution
- SPONTANEOUS EMISSION RATE
- DOTS
- DYNAMICS
- BLINKING
- GAIN