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Title: Hot exciton cooling and multiple exciton generation in PbSe quantum dots
Authors: Kumar, Manoj
Vezzoli, Stefano
Wang, Zilong
Chaudhary, Varun
Ramanujan, Raju Vijayaraghavan
Gurzadyan, Gagik G.
Bruno, Annalisa
Soci, Cesare
Keywords: PbSe
Issue Date: 2016
Source: Kumar, M., Vezzoli, S., Wang, Z., Chaudhary, V., Ramanujan, R. V., Gurzadyan, G. G., et al. (2016). Hot exciton cooling and multiple exciton generation in PbSe quantum dots. Phys. Chem. Chem. Phys., 18, 31107-31114.
Series/Report no.: Physical Chemistry Chemical Physics
Abstract: Multiple exciton generation (MEG) is a promising process to improve the power conversion efficiency of solar cells. PbSe quantum dots (QDs) have shown reasonably high MEG quantum yield (QY), although the photon energy threshold for this process is still under debate. One of the reasons for this inconsistency is the complicated competition of MEG and hot exciton cooling, especially at higher excited states. Here, we investigate MEG QY and the origin of the photon energy threshold for MEG in PbSe QDs of three different sizes by studying the transient absorption (TA) spectra, both at the band gap (near infrared, NIR) and far from the band gap energy (visible range). The comparison of visible TA spectra and dynamics for different pump wavelengths, below, around and above the MEG threshold, provides evidence of the role of the Σ transition in slowing down the exciton cooling process that can help MEG to take over the phonon relaxation process. The universality of this behavior is confirmed by studying QDs of three different sizes. Moreover, our results suggest that MEG QY can be determined by pump–probe experiments probed above the band gap.
Description: 9 p.
ISSN: 1463-9076
DOI: 10.1039/C6CP03790A
Rights: © 2016 the Owner Societies. This is the author created version of a work that has been peer reviewed and accepted for publication in Physical Chemistry Chemical Physics, published by Royal Society of Chemistry on behalf of the Owner Societies. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: [].
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SPMS Journal Articles

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