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Letter

Exciton Recombination Dynamics in CdSe Nanowires: Bimolecular to Three-Carrier Auger Kinetics

Supporting Info

István Robel,^†^‡ Bruce A. Bunker,^‡ Prashant V. Kamat,*^†^§ and Masaru Kuno*^†^§

Radiation Laboratory, Department of Chemistry and Biochemistry, Department of Chemical and Biomolecular Engineering, and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556

Nano Lett., 2006, 6 (7), pp 1344–1349

DOI: 10.1021/nl060199z

Publication Date (Web): June 2, 2006

†

Radiation Laboratory.

‡

Department of Physics.

To whom correspondence may be addressed. E-mail: pkamat@nd.edu; mkuno@nd.edu.

Department of Chemistry and Biochemistry.

Department of Chemical and Biomolecular Engineering.

Abstract

Ultrafast relaxation dynamics of charge carriers in CdSe quantum wires with diameters between 6 and 8 nm are studied as a function of carrier density. At high electron−hole pair densities above 10¹⁹ cm^-3 the dominant process for carrier cooling is the “bimolecular” Auger recombination of one-dimensional (1D) excitons. However, below this excitation level an unexpected transition from a bimolecular (exciton−exciton) to a three-carrier Auger relaxation mechanism occurs. Thus, depending on excitation intensity, electron−hole pair relaxation dynamics in the nanowires exhibit either 1D or 0D (quantum dot) character. This dual nature of the recovery kinetics defines an optimal intensity for achieving optical gain in solution-grown nanowires given the different carrier-density-dependent scaling of relaxation rates in either regime.

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