Dynamics of photoluminescence in medium-size CdSe quantum crystallites.

Pierre Lefebvre (1) , Henry Mathieu (1) , Jacques Allègre (1) , Tristan Richard (1) , Anne Combette-Roos (2) , Monique Pauthe (2) , William Granier (2)

1 GES - Groupe d'étude des semiconducteurs
2 LPCMS - Laboratoire de Physicochimie des Matériaux Solides

We have measured time-resolved photoluminescence of high-quality CdSe nanocrystallites with diameters larger than the bulk exciton Bohr diameter, embedded in sodium borosilicate matrix. Such a weak-confinement situation yields sharper lines than those usually observed for much smaller nanocrystals, due to smaller size-distribution effects. Consequently, several contributions are spectrally separated, with different temporal behaviours. Three different mechanisms are identified. The first one, corresponding to near-band-edge emissions, at the highest photon energies, is very fast ( - 50 ps) and involves `free' excitons. The second one (150 - 300 ps) involves surface trapped excitons. The third one, at rather lower energy, is a slow regime (2 - 14 ns) involving radiative and non-radiative transitions between carriers trapped at the surface sites. The observed temporal and spectral behaviours are analysed in terms of the possibility of bleaching the absorption of such medium-size nanocrystals under high photoexcitation.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Optique [physics.optics]; Micro et nanotechnologies/Microélectronique; Optique / photonique

Pierre Lefebvre, Henry Mathieu, Jacques Allègre, Tristan Richard, Anne Combette-Roos, et al.. Dynamics of photoluminescence in medium-size CdSe quantum crystallites.. Semiconductor Science and Technology, 1997, 12 (8), pp.958. ⟨10.1088/0268-1242/12/8/005⟩. ⟨hal-01260896⟩