Electron relaxation in lead-salt quantum dots

Frank W. Wise; Jeff Harbold; Stephen Clark; Byung-Ryool Hyun

doi:10.1117/12.617285

18 August 2005 Electron relaxation in lead-salt quantum dots

Frank W. Wise, Jeff Harbold, Stephen Clark, Byung-Ryool Hyun

Proceedings Volume 5929, Physical Chemistry of Interfaces and Nanomaterials IV; 59290S (2005) https://doi.org/10.1117/12.617285
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

Abstract

Recent studies of the relaxation of photoexcited electrons in PbSe quantum dots find that the relaxation of electrons from the 1P state to the 1S state occurs on the picosecond time scale, even when the states are more than 10 phonon energies apart. This ultrafast relaxation cannot be explained by mechanisms invoked to explain the absence of a phonon bottleneck in other quantum-dot materials. Linear spectroscopy reveals splitting of the lowest-energy states of PbSe quantum dots, but the splitting is inadequate to account for the ultrafast 1P-to-1S relaxation. We tentatively attribute the splitting to coupling of the equivalent L-valleys from which the quantum-dot states are derived. Fluorescence-line-narrowing experiments exhibit little narrowing, and substantial anti-Stokes fluorescence even at temperatures as low as 15 K. Finally, we observe microsecond-time-scale radiative recombination and resonant energy transfer between quantum dots. The time scale of these processes is consistent with dielectric screening of the electric field in the nanocrystals, which in turn highlights the need for better understanding of the dielectric function of a nanocrystal.

Citation Download Citation

Frank W. Wise, Jeff Harbold, Stephen Clark, and Byung-Ryool Hyun "Electron relaxation in lead-salt quantum dots", Proc. SPIE 5929, Physical Chemistry of Interfaces and Nanomaterials IV, 59290S (18 August 2005); https://doi.org/10.1117/12.617285

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