Multiexciton Absorption Cross Sections of CdSe Quantum Dots Determined by Ultrafast Spectroscopy

Summary, in English

Multiexciton absorption cross sections are important for analysis of a number of experiments, including multiple exciton generation and stimulated emisson. We present a rigorous method to determine these cross sections using transient absorption (TA) measurements. We apply the method to CdSe quantum dots (QDs) and core–shell (CdSe)ZnS QDs. The method involves measuring TA dynamics for various excitation intensities over a broad time range and analyzing the experiments in terms of a kinetic multiexciton model taking into account all contributions to the signal. In this way, we were able to quantify exciton and multiexciton absorption cross sections at different spectral positions. The absorption cross sections decrease with increasing number of excitations, qualitatively in agreement with the state-filling effective mass model but showing a slower decrease. The cross sections for single-exciton to biexciton absorption range between 57 and 99% of the ground to single-exciton cross section.

• Author: Nils Lenngren; Tommy Garting; Kaibo Zheng; Mohamed Qenawy; Noelle Lascoux; Fei Ma; Arkady Yartsev; Karel Zidek; Tönu Pullerits
• Department/s: Chemical Physics; Department of Chemistry; NanoLund: Center for Nanoscience
• Publishing year: 2013
• Language: English
• Pages: 3330-3336
• Publication/Series: The Journal of Physical Chemistry Letters
• Volume: 4
• Issue: 19
• Links: http://pubs.acs.org/doi/abs/10.1021/jz401522h; http://dx.doi.org/10.1021/jz401522h
• Document type: Journal article
• Publisher: The American Chemical Society (ACS)
• Topic: Atom and Molecular Physics and Optics
• Keywords: quantum dots; CdSe; multiexciton; absorption cross sections; femtosecond spectroscopy; transient absorption
• Status: Published
• Research group: Pullerits
• ISBN/ISSN/Other: ISSN: 1948-7185