The different nature of band edge absorption and emission in colloidal pbse/cdse core/shell quantum dots
Autor: | De Geyter, B., Justo, J., Moreels, I., Lambert, K., Smet, P.F., Van Thourhout, D., Houtepen, A.J., Grodzinska, D., de Mello Donegá, C., Meijerink, A., Vanmaekelbergh, D.A.M., Hens, Z., Condensed Matter and Interfaces, Dep Scheikunde, Sub Condensed Matter and Interfaces |
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Přispěvatelé: | Condensed Matter and Interfaces, Dep Scheikunde, Sub Condensed Matter and Interfaces |
Jazyk: | angličtina |
Rok vydání: | 2011 |
Předmět: |
Photoluminescence
Materials science Oscillator strength Condensed Matter::Other Exciton General Engineering General Physics and Astronomy Physics::Optics 02 engineering and technology Electron 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter::Mesoscopic Systems and Quantum Hall Effect 01 natural sciences 0104 chemical sciences symbols.namesake Condensed Matter::Materials Science Effective mass (solid-state physics) Quantum dot Stokes shift symbols General Materials Science Atomic physics 0210 nano-technology Luminescence |
Zdroj: | ACS Nano, 5(1), 58. American Chemical Society ACS Nano |
ISSN: | 1936-0851 |
Popis: | We present a quantitative analysis of the absorption and luminescence of colloidal PbSe/CdSe core/shell quantum dots (QDs). In absorption, both the energy and the oscillator strength of the first exciton transition coincide with that of plain PbSe QDs. In contrast, luminescence lifetime measurements indicate that the oscillator strength of the emitting transition is reduced by at least a factor of 4 compared to PbSe core QDs. Moreover, the addition of an electron scavenger quenches the PbSe/CdSe emission, while a hole scavenger does not. This implies that the electron wave function reaches the QD surface, while the hole is confined to the PbSe core. These observations are consistent with calculations based on the effective mass model, which show that PbSe/CdSe QDs are at the boundary between the type-I and quasi-type-II regime, where the electron spreads over the entire nanoparticle and the hole remains confined in the PbSe core. However, as this only leads to a minor reduction of the oscillator strength, it follows that the drastic reduction of the oscillator strength in emission cannot be explained in terms of electron delocalization. In combination with the increased Stokes shift for PbSe/CdSe QDs, this indicates that the emission results from lower energy states that are fundamentally different from the absorbing states. |
Databáze: | OpenAIRE |
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