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HL: Halbleiterphysik

HL 19: Quantum dots and wires: Optical properties II

HL 19.2: Vortrag

Dienstag, 28. März 2006, 17:30–17:45, HSZ 01

Temperature dependent fluorescence quantum efficiency of cascaded energy transfer nanocrystal structures — •S. Rohrmoser, T. Franzl, T.A. Klar, A.L. Rogach, and J. Feldmann — Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universität München

We present temperature dependent fluorescence studies of cascaded energy transfer (CET) structures made of CdTe nanocrystals. Funnel like band gap profiles are realized by applying layer-by-layer assembly to CdTe nanocrystals of distinct sizes. For high-energetic excitation, the CET structure comprising only one layer of red-emitting nanocrystals emits 4 times more red light than a reference sample of equal absorbance consisting of only red emitting nanocrystals, hence increasing the final excitation density by a factor of 28. To investigate the underlying process in more detail, temperature dependent and time resolved measurements have been performed. The results reveal an activation barrier involved in the energy transfer process and help to understand the long-lived feeding of the central layer.

1. T. Franzl, T.A.Klar, S. Schietinger, A.L. Rogach, J. Feldmann, No-dqExciton recycling in graded gap nanocrystal structuresNo-dq Nano Letters, 4, 1599 (2004)