Formation of Collective Energy States in a Dense Ensemble of Semiconductor Nanocrystals

Artemyev, Mikhail; Bibik, A. I.; Gurinovich, L. I.; Гапоненко, С. В.; Woggon, U.

doi:10.1142/9789812817990_0017

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“…In ref it was found that the room-temperature absorption of 1.8 nm CdSe nanocrystals shows an evolution from a sharp peak at 3.25 eV toward a broad absorption band centered at approximately the same energy with increasing density of the close-packed nanocrystals. A first theoretical approach based on a statistical analysis of the energy overlap integrals demonstrated a steady increase of the number of delocalized states in ensembles of interacting quantum dots when the size of the CdSe nanocrystals and the interparticle distance are smaller than ∼2 nm and ∼4 nm, respectively . Delocalization of electron−hole states has clearly been observed until now only for ultrasmall, nearly monodisperse nanocrystals having small electron or hole effective mass.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Study of Electronic States in an Ensemble of Close-Packed CdSe Nanocrystals

Artemyev

Woggon²,

Jaschinski³

et al. 2000

J. Phys. Chem. B

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130

116

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Nearly monodisperse CdSe quantum dots of 1.8 nm in size were synthesized and capped with a surface monolayer of 1-thioglycerol. The optical properties of thin films made from these matrix-free close-packed quantum dots were studied at different temperatures and electric field strengths and compared with isolated quantum dots of the same size embedded in a PMMA matrix. The broadening and red shift of the optical transitions observed in absorption and excitation spectroscopy for the ensemble of close-packed quantum dots is explained by the formation of collective electronic states between interacting nanocrystals. The reversible collapse of these extended electronic states into localized states was demonstrated for the close-packed quantum dots by applying an external electric field.

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Section: Introductionmentioning

confidence: 99%