Femtosecond cooling of hot electrons in CdSe quantum-well platelets.
| Autor: | Sippel P; †Institute for Solar Fuels, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany., Albrecht W, van der Bok JC, Van Dijk-Moes RJ, Hannappel T; ∥Institut für Physik, Technische Universität Ilmenau, Postfach 100565, D-98684 Ilmenau, Germany., Eichberger R; †Institute for Solar Fuels, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany., Vanmaekelbergh D |
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| Jazyk: | angličtina |
| Zdroj: | Nano letters [Nano Lett] 2015 Apr 08; Vol. 15 (4), pp. 2409-16. Date of Electronic Publication: 2015 Mar 17. |
| DOI: | 10.1021/nl504706w |
| Abstrakt: | Semiconductor quantum wells are ubiquitous in high-performance optoelectronic devices such as solar cells and lasers. Understanding and controlling of the (hot) carrier dynamics is essential to optimize their performance. Here, we study hot electron cooling in colloidal CdSe quantum-well nanoplatelets using ultrafast two-photon photoemission spectroscopy at low excitation intensities, resulting typically in 1-5 hot electrons per platelet. We observe initial electron cooling in the femtosecond time domain that slows down with decreasing electron energy and is finished within 2 ps. The cooling is considerably faster at cryogenic temperatures than at room temperature, and at least for the systems that we studied, independent of the thickness of the platelets (here 3-5 CdSe units) and the presence of a CdS shell. The cooling rates that we observe are orders of magnitude faster than reported for similar CdSe platelets under strong excitation. Our results are understood by a classic cooling mechanism with emission of longitudinal optical phonons without a significant influence of the surface. |
| Databáze: | MEDLINE |
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