We report on the temperature dependence of the photoluminescence (PL) spectrum and of the PL relaxation dynamics for colloidal CdSeZnS core/shell quantum dots (QDs) embedded in an inert polystyrene matrix. We demonstrate that the confinement energy in the QDs is independent of the temperature. The coupling with both acoustic and optical phonons is also studied. Quantum confinement results in a strong increase of the exciton-acoustic-phonon coupling constant, up to 71μeVK, and in a reduced exciton-longitudinal-optical (LO)-phonon coupling constant, down to 21meV, with respect to bulk CdSe. In addition, we demonstrate that the main nonradiative process that limits the quantum efficiency of the QD at room temperature is the thermal escape from the dot assisted by scattering with four LO phonons. Thermally activated trapping in surface states is also observed at low temperature, with an activation energy of about 15meV. © 2005 The American Physical Society.
Temperature dependence of the photoluminescence properties of colloidal CdSeZnS core/shell quantum dots embedded in a polystyrene matrix
Valerini D.;
2005-01-01
Abstract
We report on the temperature dependence of the photoluminescence (PL) spectrum and of the PL relaxation dynamics for colloidal CdSeZnS core/shell quantum dots (QDs) embedded in an inert polystyrene matrix. We demonstrate that the confinement energy in the QDs is independent of the temperature. The coupling with both acoustic and optical phonons is also studied. Quantum confinement results in a strong increase of the exciton-acoustic-phonon coupling constant, up to 71μeVK, and in a reduced exciton-longitudinal-optical (LO)-phonon coupling constant, down to 21meV, with respect to bulk CdSe. In addition, we demonstrate that the main nonradiative process that limits the quantum efficiency of the QD at room temperature is the thermal escape from the dot assisted by scattering with four LO phonons. Thermally activated trapping in surface states is also observed at low temperature, with an activation energy of about 15meV. © 2005 The American Physical Society.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
