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HL: Halbleiterphysik
HL 62: Photonische Kristalle IV
HL 62.11: Vortrag
Mittwoch, 9. März 2005, 13:15–13:30, TU P164
Interplay between Auger and ionisation processes in nanocrystal quantum dots — •Robert Kraus1, Pavlos Lagoudakis1, Dmitry Talapin2, Andrey L. Rogach1, John M. Lupton1, Jochen Feldmann1, and Horst Weller2 — 1Lehrstuhl für Photonik und Optoelektronik, Ludwig-Maximilians-Universität München — 2Institut für Physikalische Chemie, Universität Hamburg
A detailed understanding of the radiative and non-radiative decay channels in semiconductor nanocrystal quantum dots (NQDs) is necessary for tuning their fluorescence dynamics in photonic structures. In photonically confined systems it is particularly important to know if there is an influence of increased excitation density on the decay dynamics, as such an intrinsic effect may mark extrinsic changes in lifetime due to photonic confinement [1]. As a first step we present here spectrally resolved fluorescence decay measurements on CdSe/ZnS core/shell NQDs embedded in a polystyrene matrix. We show that there is an monotonic increase of the fluorescence decay rate with excitation power in the high excitation density regime. Our results suggest that Auger recombination accelerates ionisation processes that lead to the formation of dark, non-emissive nanocrystal states. A detailed kinetic model is proposed in the quantised Auger regime describing these experimental observations and providing an estimate of the Auger assisted ionisation rates. We conclude that great caution has to be exerted when employing NQDs as light sources under photonic confinement due to their intrinsic field strength dependence of the fluorescence decay. [1] P. Lodahl et al., Nature 430, 654 (2004)