Center for Excitonics Seminar Series Presents:
A hybrid molecular-nanocrystal platform for photon upconversion
May 16, 2017 at 4:30pm/36-428
Ming Lee Tang
University of California, Riverside/ Department of Chemistry, and Material Science and
Engineering
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http://www.rle.mit.edu/excitonics/wp-content/uploads/2016/10/mingleetang.2.…]
Third generation photovoltaics are inexpensive modules that promise power conversion
efficiencies (PCEs) exceeding the thermodynamic Shockley-Queisser limit, perhaps by using
up- or down-converters, intermediate band solar cells, tandem cells, hot carrier devices,
or multi-exciton generation (MEG). Here, I introduce a hybrid platform comprised of
semiconductor nanocrystals and organic semiconductor molecules that can efficiently
upconvert light of visible and infrared wavelengths, at excitation densities below the
solar flux. For example, colloidally synthesized core-shell lead sulfide -cadmium sulfide
nanocrystals (NCs), in combination with tetracene derivatives, absorb near infrared (NIR)
light and emit visible light at 560 nm with an upconversion quantum yield (QY) of 8.4 ±
1.0 %. This is achieved with NIR cw excitation at 3.2 mW/cm2, approximately three times
lower than the available solar flux and about a million times lower excitation densities
than state of the art lanthanide-based upconversion materials, for comparable QYs. The
molecular and nanocrystal engineering here paves the way towards utilizing this hybrid
upconversion platform in photovoltaics, photodetectors and photocatalysis.
Ming Lee Tang is the Assistant Professor in the department of Chemistry, and Material
Science and Engineering at the University of California, Riverside. Her research group
focuses on the design, synthesis and characterization of novel hybrid organic-inorganic
materials. Emphasis is on the synthesis of tailor-made organic ligands designed to
control, enhance or mediate the optoelectronic properties of nanocrystals (NCs). The use
of synthetic organic chemistry in ligand design enables desired properties to be embedded
in a modular and scalable manner. These ligands allow the size, shape and material
dependent properties of the NCs to be harnessed for energy, metamaterial and
optoelectronic applications. The synthetic expertise in this group is complemented by
single molecule spectroscopic and thin-film current-voltage measurements.
The Center For Excitonics Is An Energy Frontier Research Center Funded By The U.S.
Department Of Energy,
Office Of Science And Office Of Basic Energy Sciences
Light refreshments will be served.