Tunable Infrared Phosphors
Using Cu Doping in Semiconductor
Nanocrystals: Surface Electronic Structure Evaluation
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Abstract
In this Letter, we report the study of the effect of
ligands on
the surface electronic structure of the nanocrystal by exploiting
the mechanism of the Cu-related optical transition, obtained by coupling
the nanocrystal conduction band to the Cu ion state in Cu-doped II–VI
semiconductor nanocrystals. Systematic study of steady-state luminescence
and lifetime decay dynamics of this Cu-related emission in cadmium-based
chalcogenides shows that the role of oleic acid in surface passivation
is unexpectedly quite different for various chalcogenides. Further,
using these leads in Cu-doped CdS nanocrystals, we develop near-infrared-emitting
phosphor materials that have tunable, high quantum yield (∼35%)
emission with a single-exponential lifetime decay. Surprisingly, unlike
the emission from other Cu-doped II–VI nanocrystals, emission
from Cu doping in CdS nanocrystals is found to exhibit high thermal
stability, being essentially unchanged up to 100 °C, making them
more viable for use in various practical applications