29 Mar
2017
29 Mar
'17
10:56 a.m.
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Micro-nano Seminar Series
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Wednesday, March 29, 2017
4:00 pm - Room 3-270
Dr. Jongseung Yoon
Department of Chemical Engineering and Materials Science
Department of Electrical Engineering
University of Southern California
New Approaches for Using III-V Compound Semiconductors in Photovoltaic and
Photoelectrochemical Solar Energy Conversion
Abstract
Due to their highly favorable materials properties such as direct bandgap, appropriate
bandgap energy against solar spectrum, and high electron mobilities, epitaxially grown
III-V compound semiconductors have provided unmatched performance in solar energy
harvesting. However, their large-scale deployment in terrestrial photovoltaics and solar
fuel generation remains as a daunting challenge mainly due to the prohibitively high cost
of growing device-quality epitaxial materials. In this regard, unconventional ways to
exploit III-V compound semiconductors can create novel engineering designs, device
functionalities, and cost structures, each with significant values in the next generation
solar energy conversion technologies. In the first part of my talk, I will provide an
overview of recent advances in materials design and fabrication concepts towards
cost-efficient III-V photovoltaic systems based on multilayer-grown, ultrathin,
nanostructured GaAs solar cells. Hexagonally periodic TiO2 nanoposts directly implemented
on the window layer of GaAs solar cells served as a lossless diffractive coating for
antireflection, diffraction, and light trapping in conjunction with a co-integrated
back-surface reflectors, providing 20.8% one-sun efficiency with solar cells that have the
thickness of active layer (emitter + base = 300 nm) more than 10 times thinner than
conventional devices. In the second part, I will present a type of III-V photoelectrode
systems for solar fuel generation based on heterogeneously integrated assemblies of
epitaxially grown III-V materials. Specialized epitaxial design together with a bifacial
electrode configuration decoupling optical and reactive interfaces enabled facile,
independent control and optimization of light absorption, carrier transport, charge
transfer, and materials stability in GaAs-based photoelectrodes, allowing for high
efficiency (~13.1% STH), long lifetime (~ 8 days) operation of solar-driven water
splitting for hydrogen generation.
Biography
[cid:image005.jpg@01D2A87B.283F5A50]Dr. Jongseung Yoon is an assistant Professor in the
Mork Family Department of Chemical Engineering and Materials Science at the University of
Southern California. He received a Ph.D. degree in Materials Science and Engineering from
the Massachusetts Institute of Technology in 2006, and B.S. degree in Polymer Science from
Seoul National University in 1996, respectively. Prior to joining USC, Prof. Yoon was a
Beckman Institute Postdoctoral Fellow at the University of Illinois at Urbana-Champaign.
His current research focuses on tailoring and understanding novel electrical, optical,
electrochemical, and thermal properties of nanostructured inorganic single-crystalline
semiconductor materials and exploiting them as synergistic materials building blocks into
unusual format device implementation in areas ranging from photovoltaics,
photoelectrochemical water splitting, to flexible/stretchable optoelectronics for
skin-mountable/implantable sensing and therapeutic systems. Prof. Yoon is a recipient of
DARPA Young Faculty Award in 2012 and Hanwha Non-Tenure Faculty Award in 2015.
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Host: Prof. Jeehwan Kim
*Please email Prof. Kim at jeehwan@mit.edu<mailto:jeehwan@mit.edu> if you have any
questions regarding this seminar.
Refreshments provided.
Thank you,
Emilie Heilig
Massachusetts Institute of Technology
77 Massachusetts Ave, 3-359
(32 Vassar St, 3-359 for packages)
Cambridge, MA 02139
P: 617-253-2883
