Ensemble Brightening and Enhanced Quantum Yield in Size-Purified Silicon Nanocrystals

We report on the quantum yield, photoluminescence (PL) lifetime, and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reductio...

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Bibliographic Details
Published in:ACS nano 2012-08, Vol.6 (8), p.7389-7396
Main Authors: Miller, Joseph B, Van Sickle, Austin R, Anthony, Rebecca J, Kroll, Daniel M, Kortshagen, Uwe R, Hobbie, Erik K
Format: Article
Language:English
Subjects:
Brightening
Computer simulation
Crystallization - methods
Emergence
Light
Luminescent Measurements
MATERIALS SCIENCE
Materials Testing
nanocrystalline silicon
Nanocrystals
Nanostructure
Nanostructures - chemistry
Nanostructures - ultrastructure
Particle Size
Photoluminescence
photoluminescent stability
polydispersity
Quantum confinement
Quantum Theory
quantum yield
Reduction
Scattering, Radiation
Silicon
Silicon - chemistry
Silicon - isolation & purification
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Summary:We report on the quantum yield, photoluminescence (PL) lifetime, and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reduction in PL line width and the emergence of entropic order in dry nanocrystal films. We find excellent agreement with the anticipated trends of quantum confinement in nanocrystalline silicon, with a solution quantum yield that is independent of nanocrystal size for the larger fractions but decreases dramatically with size for the smaller fractions. We also find a significant PL enhancement in films assembled from the fractions, and we use a combination of measurement, simulation, and modeling to link this “brightening” to a temporally enhanced quantum yield arising from SiNC interactions in ordered ensembles of monodisperse nanocrystals. Using an appropriate excitation scheme, we exploit this enhancement to achieve photostable emission.
ISSN:1936-0851
1936-086X
DOI:10.1021/nn302524k