Approaches to ultrahigh efficiency solar energy conversion webinar

California Institute of Technology

Hameetman Auditorium at the Cahill Center [map]

LIVE Internet Broadcast

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The recorded presentations and panel discussion are now available for online viewing.


The Light-Material Interactions in Energy Conversion Energy Frontier Research Center (LMI-EFRC) is excited to offer this free public webinar on Approaches to Ultrahigh Efficiency Solar Energy Conversion.


The LMI-EFRC is made up of world leaders creating new optical materials and innovative photonic designs that engineer and control light-material interactions, with the goal of achieving ultrahigh efficiency solar cells. This webinar will feature presentations and an interactive panel discussion with some of our photovoltaic experts from California Institute of Technology, University of California, Berkeley, and University of Illinois at Urbana-Champaign. We will have interactive question and answer sessions after each of the presentations and during the panel discussion.



Harry Atwater

8:30-9:00 am PST

Photonic Design Principles for Ultrahigh-Efficiency Photovoltaics

Harry Atwater, Howard Hughes Professor and Professor of Applied Physics and Materials Science; Director, Resnick Sustainability Institute

California Institute of Technology

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Abstract: Ever since serious scientific thinking went into improving the efficiency of photovoltaic energy conversion more than 50 years ago, thermodynamics has been used to assess the limits to performance, guiding advances in materials science and photovoltaic technology.   Photovoltaics have advanced considerably, resulting in single-junction solar cells with a record efficiency of 28.3% and multi-junction cells with an efficiency of 43.5%. As impressive as these advances are, these record efficiencies and also today’s manufactured cell efficiencies in the 10–18% range fall far short of the thermodynamic limits.  Why such a large gap? There is no fundamental reason, and in this webinar, I will discuss methods for systematically addressing the thermodynamic efficiency losses in current photovoltaics that can enable a next phase of photovoltaic science and engineering – ultrahigh efficiency photovoltaics.  This development takes advantage of recent advances in the control of light at the nanometer and micron length scales, coupled with emerging materials fabrication approaches, and will allow the development of solar cells with efficiencies in the 50–70% range.


Biography: Dr. Harry A. Atwater is currently Howard Hughes Professor and Professor of Applied Physics and Materials Science at the California Institute of Technology.  His research interests center around two interwoven research themes: photovoltaics and solar energy; and plasmonics and optical metamaterials.  Atwater and his group have been active in photovoltaics research for more than 20 years.  Recently they have created new photovoltaic devices, including silicon wire array solar cells, and transferred-layer designs for III-V semiconductor and multijunction cells.  They are making exciting advances in plasmonic light absorber structures for III-V compound and silicon thin films.  Atwater is an early pioneer in surface plasmon photonics; he gave the name to the field of plasmonics in 2001.  He has authored or co-authored over 200 publications, and his group’s developments in the solar and plasmonics field have been featured in Scientific American and in research papers in Science, Nature Materials, Nature Photonics and Advanced Materials. Atwater received his S.B. (1981), S.M. (1983), and Ph.D. (1987) in Electrical Engineering from the Massachusetts Institute of Technology.  He currently serves as Director of the DOE Energy Frontier Research Center on Light-Material Interactions in Solar Energy Conversion and is the Director of the Resnick Sustainability Institute, Caltech’s largest endowed research program focused on energy.  Atwater is founder and chief technical advisor for two venture-backed photovoltaic companies: Caelux Solar Energy in Pasadena, CA, and Alta Devices in Santa Clara, CA which is developing a transformational high efficiency/low cost photovoltaics technology.  Atwater is an MRS Fellow and has been honored by awards including the ENI Award in Renewable and Nonconventional Energy in 2012; Green Photonics Award in Renewable Energy Generation, SPIE 2012; Popular Mechanics Breakthrough Award, 2010; MRS Kavli Lecturer in Nanoscience in 2010; Joop Los Fellowship from the Dutch Society for Fundamental Research on Matter in 2005.


John Rogers

9:00-9:30 am PST

Microscale Solar Cells for Macroscale Power Generation

John A. Rogers, Lee J. Flory-Founder Chair Professor in Engineering; Director, Frederick Seitz Materials Research Laboratory

University of Illinois at Urbana-Champaign

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Solar modules that involve large, interconnected collections of small, ultrathin photovoltaic cells offer unique options in engineering design. This talk describes assembly strategies and optical aspects for this type of technology, as implemented with silicon and compound semiconductors derived from wafer-scale sources of material. Examples include modules that exploit optical concentration based on (1) focusing micro-optics to achieve world record efficiencies for utility-scale power generation, and (2) thin, plastic luminescent waveguides to enable flexible, rugged mechanics for portable energy.


Biography: Dr. John A. Rogers is the Lee J. Flory-Founder Chair Professor in Engineering at the University of Illinois at Urbana-Champaign. Rogers' research includes fundamental and applied aspects of nano and molecular scale fabrication as well as materials and patterning techniques for unusual format electronics and photonic systems. Current research focuses on soft materials for flexible ‘macroelectronic’ circuits, nanophotonic structures, microfluidic devices, and microelectromechanical systems. Dr. Rogers has published over 200 papers, and is co-inventor on over 70 patents and patent applications, more than 40 of which are licensed or in active use by large companies (e.g. Lucent Technologies) and startups (e.g. Active Impulse Systems and Semprius). Dr. Rogers has been recognized with many awards including the Department of Defense National Security Science and Engineering Faculty Fellow (2009), MacArthur Fellow - John D. and Catherine T. MacArthur Foundation (2009), IEEE Fellow (2010), and Member of the National Academy of Engineering (2011). He serves, or has recently served, on several Editorial Boards, including those for Applied Physics Letters, Journal of Applied Physics and Nano Letters. He also is Associate Editor of IEEE Transactions on Nanotechnology, and SPIE Journal of Microlithography, Microfabrication and Microsystems.


Eli Yablonovitch

9:30-10:00 am PST

The Multi-Spectral Opto-Electronic Physics of Solar Cells, Efficiencies >30%

Eli Yablonovitch, Professor of Electrical Engineering and Computer Sciences, University of California, Berkeley; Director of the NSF Center for Energy Efficient Electronics Science (E 3S)

Lawrence Berkeley National Laboratory

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[m4v] [mp3]
It appears now that single-junction solar cells can be produced in the 25%-30% efficiency range at low cost, for example by GaAs thin film liftoff. The high efficiency benefits especially from the concept of luminescence extraction efficiency, to boost the voltage. As progress is made in single-junction solar cells the next big step becomes the 30%-50% efficiency range. It becomes imperative to exploit each solar spectral component as efficiently as possible. The questions arise whether to split the solar spectrum vertically as in a tandem, or horizontally as in a diffractive splitter. At the same time, this is complicated by a strong motivation to retain the voltage benefit associated with good luminescence extraction. The challenge then is to sift through all of the technical options, to identify the right mainstream photovoltaic technologies for the 30%-50% efficiency range.


Biography: Professor Eli Yablonovitch is the Director of the NSF Center for Energy Efficient Electronics Science (E 3S), a multi-University Center based at Berkeley. He received his Ph.d. degree in Applied Physics from Harvard University in 1972. He worked for two years at Bell Telephone Laboratories, and then became a professor of Applied Physics at Harvard. In 1979 he joined Exxon to do research on photovoltaic solar energy. Then in 1984, he joined Bell Communications Research, where he was a Distinguished Member of Staff, and also Director of Solid-State Physics Research. In 1992 he joined the University of California, Los Angeles, where he was the Northrop-Grumman Chair Professor of Electrical Engineering. Then in 2007 he became Professor of Electrical Engineering and Computer Sciences at UC Berkeley, where he holds the James & Katherine Lau Chair in Engineering. Prof. Yablonovitch is a Fellow of the IEEE, the Optical Society of America and the American Physical Society. He is a Life Member of Eta Kappa Nu, and a Member of the National Academy of Engineering and the National Academy of Sciences. He has been awarded the Adolf Lomb Medal, the W. Streifer Scientific Achievement Award, the R.W. Wood Prize, the Julius Springer Prize, and the Mountbatten Medal. He also has an honorary Ph.d. from the Royal Institute of Technology, Stockholm Sweden. In his photovoltaic research, Yablonovitch introduced the 4n 2 light-trapping factor that is used commercially in almost all high performance solar cells. Yablonovitch introduced the idea that strained semiconductor lasers could have superior performance due to reduced valence band (hole) effective mass. Today, almost all semiconductor lasers use this concept, including telecommunications lasers, DVD players, and red laser pointers. Yablonovitch is regarded as one of the Fathers of the Photonic BandGap concept, and coined the term "Photonic Crystal".


10:00-10:30 am PST

Panel Discussion: Future Directions for Light-Material Interactions in Photovoltaics

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Paul Alivisatos

Paul Alivisatos, Professor of Chemistry and Materials Science, Larry and Diane Bock Professor of Nanotechnology; Director, Lawrence Berkeley National Laboratory

Lawrence Berkeley National Laboratory

Biography: Dr. Paul Alivisatos serves as the seventh director of Lawrence Berkeley National Laboratory, succeeding Steve Chu when he was sworn in as the U.S. Secretary of Energy. Alivisatos has led a distinguished career in chemistry and nanoscience research.  He has made groundbreaking contributions to the fundamental physical chemistry of nanocrystals, including the synthesis of size and shape controlled nanoscystals, and studies of the optical, electrical, structural, and thermodynamic properties.   He has demonstrated key applications of nanocrystals in biological imaging and renewable energy.  He is currently the Larry and Diane Bock Professor of Nanotechnology and is a professor in the departments of materials science and chemistry at UC Berkeley.  (Larry and Diane Bock are the founders and main leaders of the U.S.A. Science & Engineering Festival, held on the Mall in Washington, DC. The Kavli Foundation sponsors the Kavli Science Video Contest for this Festival.) He is the recipient of the Linus Pauling Medal, Ernest Orlando Lawrence Award, the Eni Italgas Prize for Energy and Environment, the Rank Prize for Optoelectronics, the Wilson Prize, the Coblentz Award for Advances in Molecular Spectroscopy, the American Chemical Society Award for Colloid and Surface Science, the Von Hippel Award of the Materials Research Society, the Wolf Prize in Chemistry which he shares with Charles Lieber, and most recently the 2012 Niki Award, awarded by Athens Information Technology (AIT). He received a Bachelor's degree in Chemistry in 1981 from the University of Chicago and Ph.D. in Chemistry from UC Berkeley in 1986.  


Paul Braun

Paul V. Braun, Ivan Racheff Professor of Materials Science and Engineering

University of Illinois at Urbana-Champaign

Biography: Professor Paul V. Braun is the Ivan Racheff Professor of Materials Science and Engineering, and an affiliate of the Frederick Seitz Materials Research Laboratory, the Beckman Institute forAdvanced Science and Technology, the Department of Chemistry, the Micro and Nanotechnology Laboratory and the Mechanical Science and Engineering Department at the University of Illinois at Urbana-Champaign. Prof. Braun's research focuses on the synthesis and properties of 3D architectures with a focus on materials with unique optical, electrochemical, thermal, and mechanical properties. Prof. Braun received his B.S. degree with distinction from Cornell University in 1993, and his Ph.D. in Materials Science and Engineering from Illinois in 1998. Following a postdoctoral appointment at Bell Labs, Lucent Technologies, he joined the faculty at Illinois in 1999. Prof. Braun has co-authored a book, authored over 100 peer-reviewed publications, and has been awarded multiple patents. He is the recipient of the Young Alumnus Award (2011), the Friedrich Wilhelm Bessel Research Award (2010), the Stanley H. Pierce Faculty Award (2010), Beckman Young Investigator Award (2001), a 3M Nontenured Faculty Award, the 2002 Robert Lansing Hardy Award from TMS, the Xerox Award for Faculty Research (2004, 2009), and multiple teaching awards. In 2006, he was named a University Scholar by the University of Illinois , and in 2011 was named the Ivan Racheff Professor of Materials Science and Engineering.


Harry Atwater

Nate Lewis, George L. Argyros Professor of Chemistry; Director, Joint Center for Artificial Photosynthesis

California Institute of Technology

Biography: Dr. Nate Lewis is Professor of Chemistry at the California Institute of Technology since 1991. Professor Lewis since 2010 has served as Principal Investigator of the Joint Center for Artificial Photosynthesis, the DOE’s Energy Innovation Hub in Fuels from Sunlight, and since 1992 the Beckman Institute Molecular Materials Resource Center. His research interests include artificial photosynthesis and electronic noses. Nate continues to study ways to harness sunlight and generate chemical fuel by splitting water to generate hydrogen. He is developing the electronic nose, which consists of chemically sensitive conducting polymer film capable of detecting and quantifying a broad variety of analytes. Technical details focus on light-induced electron transfer reactions, both at surfaces and in transition metal complexes, surface chemistry and photochemistry of semiconductor/liquid interfaces, novel uses of conducting organic polymers and polymer/conductor composites, and development of sensor arrays that use pattern recognition algorithms to identify odorants, mimicking the mammalian olfaction process.