Excitation resolved color conversion of CdSe/ZnS core/shell quantum dot solids for hybrid white light emitting diodes

Date
2009-04-28
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Source Title
Journal of Applied Physics
Print ISSN
0021-8979
Electronic ISSN
Publisher
American Institute of Physics
Volume
105
Issue
8
Pages
083112-1 - 083112-5
Language
English
Type
Article
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Abstract

In this paper, for their use as nanoluminophors on color-conversion white light emitting diodes (LEDs), we present spectrally resolved relative quantum efficiency and relative color (photon) conversion efficiency of CdSe/ZnS core/shell nanocrystal (NC) emitters in the solid-state film. We observe that both the averaged relative quantum efficiency and the averaged relative photon conversion efficiency of these NC solids increase with the increasing photon pump energy. Therefore, the excitation LED platform emitting at shorter wavelengths facilitates such NC luminophor solids to be more efficiently pumped optically. Furthermore, we investigate the spectral time-resolved spectroscopy of NCs in solution and in film with 0.4-2.4 nmol integrated number of NCs in the spectral range of 610-660 nm. We observe that the average lifetime of NCs increases toward longer wavelengths as the number of in-film NCs increases. With the increased amount of NCs, the average lifetime increases even further and the emission of NCs is shifted further toward red. This is attributed to the enhanced nonradiative energy transfer between these NCs due to the inhomogeneous size distribution. Thus, in principle, for fine tuning of the collective color of NCs for color-conversion LEDs, it is important to control the energy transfer by changing the integrated number of NCs.

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Keywords
Cadmium Compounds, Ii-vi semiconductors, Light emitting diodes, Nanostructured materials, Phosphors, Selenium compounds, Semiconductor thin films, Time resolved spectra, Wide band gap semiconductors, Zinc compounds
Citation
Published Version (Please cite this version)