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Difference in hot carrier cooling rate between Langmuir-Blodgett and drop cast PbS QDs films due to strong electron-phonon coupling

Abstract

Abstract: The carrier dynamics of lead sulphide quantum dots (PbS QDs) drop cast film and closely packed ordered Langmuir-Blodgett film are studied with ultra-fast femtosecond transient absorption spectroscopy. The photo-induced carrier temperature is extracted from transient absorption spectra and monitored as a function of time delay. The cooling dynamics of carriers in PbS QDs suggest a reduction of carrier energy loss rate at longer time delays through the retardation of the longitudinal optical (LO) phonon decay due to partial heating of acoustic phonon modes. A slowed hot carrier cooling time up to 116 ps is observed. A faster cooling rate was also observed in the highly compact Langmuir-Blodgett film due to the enhanced carrier-LO phonon coupling strength arising from the Coulombic interaction in neighboring QDs, which is verified by temperature dependent steady state PL measurements.

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Publication details

The article was received on 19 Jul 2017, accepted on 28 Sep 2017 and first published on 29 Sep 2017


Article type: Paper
DOI: 10.1039/C7NR05247B
Citation: Nanoscale, 2017, Accepted Manuscript
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    Difference in hot carrier cooling rate between Langmuir-Blodgett and drop cast PbS QDs films due to strong electron-phonon coupling

    W. Cao, Y. Lin, R. Patterson, X. Wen, P. C. Tapping, T. W. Kee, B. Puthen-Veettil, P. Zhang, Z. Zhang, Q. Zhang, P. Reece, S. Bremner, S. shrestha, G. Conibeer and S. Huang, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR05247B

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