posted on 2015-05-13, 00:00authored byJason K. Cooper, Sheraz Gul, Sarah A. Lindley, Junko Yano, Jin Z. Zhang
Semiconductor
quantum dots (QDs) with stable, oxidation resistant, and tunable photoluminescence
(PL) are highly desired for various applications including solid-state
lighting and biological labeling. However, many current systems for
visible light emission involve the use of toxic Cd. Here, we report
the synthesis and characterization of a series of codoped core/shell
ZnSe/ZnS QDs with tunable PL maxima spanning 430−570 nm (average
full width at half-maximum of 80 nm) and broad emission extending
to 700 nm, through the use of Cu+ as the primary dopant
and trivalent cations (Al3+, Ga3+, and In3+) as codopants. Furthermore, we developed a unique thiol-based
bidentate ligand that significantly improved PL intensity, long-term
stability, and resilience to postsynthetic processing. Through comprehensive
experimental and computational studies based on steady-state and time-resolved
spectroscopy, electron microscopy, and density functional theory (DFT),
we show that the tunable PL of this system is the result of energy
level modification to donor and/or acceptor recombination pathways.
By incorporating these findings with local structure information obtained
from extended X-ray absorption fine structure (EXAFS) studies, we
generate a complete energetic model accounting for the photophysical
processes in these unique QDs. With the understanding of optical,
structural, and electronic properties we gain in this study, this
successful codoping strategy may be applied to other QD or related
systems to tune the optical properties of semiconductors while maintaining
low toxicity.