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Events for September 10, 2010
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Distinguished Speaker Series
Fri, Sep 10, 2010 @ 10:00 AM - 11:00 PM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
Speaker: Supratik Guha - Director of Physical Sciences, IBM T. J. Watson Research Center
Talk Title: Photovoltaics Research at IBM
Abstract: In this talk I will describe research in three different areas in photovoltaics that are ongoing at IBM Research--concentrator photovoltaics, solar cells from earth abundant materials, and nanowire based solar cells. Â Concentrator photovoltaics, which can have the highest power conversion efficiencies at the system level, has suffered from the lack of the benefits of economies of scale, which is rapidly allowing flat panel systems to lower costs. Yet, provided the manufacturing of these systems can be highly automated, CPV stands a very good chance for cost reduction--the challenge here is one of simplicity of construction, weight reduction and optical and thermal system design. Â Earth abundant thin films, that can support manufacturing rates of >10-20 GW/yr is an important (and increasingly fashionable) topic of research. Â I will describe results that we have in this area with the copper-zinc-tin-sulfide (CZTS) system. Â Finally, I will describe some results of our work on silicon nanowire photovoltaics, where the benefits are one of enhanced light trapping and, possibly, the ability to effectively have devices that are small enough so that generated carriers can be collected without relying upon minority carrier diffusion. Â However, a big drawback here has been the detrimental role of surfaces and interfaces that has prevented nanowire solar cells (and other nanostructured solar cells) from demonstrating high efficiencies.
Biography: Supratik Guha is the Director of the Physical Sciences Department at IBM Research and in this capacity is responsible for overseeing IBMâs worldwide research strategy in the physical sciences. His technical work, over the past dozen years, has been in the area of new materials for silicon microelectronics where he has been responsible for some of the key material advances that are now part of IBM's common platform high k metal gate technology, developed by IBM with its alliance partners, and representing major changes in the way that a silicon transistor is built.  More recently, his own research work has been on new materials for energy conversion devices.  As a manager, he has established many successful research programs at IBM including ones in silicon nanophotonics, thermal physics, photovoltaics, and nanowire based technologies.  Supratik  is also an adjunct professor of materials science at Columbia University.  Prior to joining IBM in 1995, he worked on semiconductor lasers at the 3M Corporate Research Labs from 1992-95  He received his Ph.D. in materials science from the University of Southern California in 1991, and a B. Tech in Metallurgical Engineering from the Indian Institute of Technology, Kharagpur, in 1985.  He is a Fellow of the American Physical Society.
Host: Center for Energy Nanoscience and Technology
Location: Seaver Science Library (SSL) - 150
Audiences: Everyone Is Invited
Contact: Marilyn Poplawski
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Two Studies: Plasmon-Enhanced Absorption in Silicon Substrate and On the Universal Behavior of Electro-Optical Materials
Fri, Sep 10, 2010 @ 03:00 PM - 04:00 PM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
Speaker: Uzi Efron , Professor/Ben-Gurion University, Negev, Beer-Sheva, Israel.
Talk Title: Two Studies: Plasmon-Enhanced Absorption in Silicon Substrate and On the Universal Behavior of Electro-Optical Materials
Abstract:
1. Computer simulation studies of absorption enhancement in a silicon substrate by nanoshell-related Localized Surface Plasmon Resonance (LSPR) based on a Finite Difference Time Domain (FDTD) analysis will be presented. The results of these studies show significant enhancement of over 4X in the near band gap spectral region of Si, using 30nm diameter, 2-Dimensional,cylindrical Ag nanoshell structure. The studies also indicate a clear advantage of the cylindrical nanoshell structure over that of a completely filled Ag-nano- cylinders. The enhancement was studied as a function of the metallic shell thickness. The results suggest that the main enhancement mechanism in this case of cylindrical nanoshells embedded in Si substrate, is that of field-enhanced absorption caused by the strongly LSPR-enhanced electric field, extending into the silicon substrate.
2. Electro-optical light modulators are key components for a number of optical systems including displays, optical interconnects, optical processing, optical beam steering and adaptive optics . The performance of these modulators can be characterized by three main physical parameters: The electro-optical coefficient, the RF frequency bandwidth and the optical spectral bandwidth. A recent study [1] has shown that the product of these three parameters, which we term âSusceptibility-Bandwidth Productâ (SBP), is remarkably constant within 1-2 orders of magnitude, across a wide range of different material systems, including Liquid Crystals (LC) , Solid State Electro-Optical Materials and Multiple Quantum Well structures. This, despite the fact that all three parameters vary over many orders of magnitude across this range of materials. The feasibility of the SBP constancy based on material stability considerations has already been proposed several years ago [2]. The main purpose of this study was to perform a detailed study of the SBP in Nematic Liquid Crystal (NLC) materials based on the electro-optics of the electrically controlled birefringence effect. The work includes the derivation of a theoretical expression for the SBP in NLC materials, as well as its comparison to experimental data. The results are found to be in good agreement with the theoretical prediction for this product.
References
1. U. Efron, in Handbook of Opto-Electronics, J.P. Dakin and R.G.W.Brown, Editors, Taylor and Francis, London, 2006, Vol. 2.
2. U. Efron âSpatial Light Modulators and Applications for Optical Information Processingâ, in âReal Time Signal Processing for Industrial Applicationsâ, Proc. SPIE, vol.960 (1988).
Biography: Uzi Efron (Mâ87) received the B.Sc., M.Sc., and Ph.D. degrees from Tel Aviv University, Tel Aviv, Israel, in 1967, 1970, and 1976, respectively, all in physics. He was a Principal Scientist at Hughes Research Laboratories, Malibu, CA, where he conducted research on photo-activated and charge-coupled device (CCD)-addressed liquid crystal light valves as well as multiple-quantum-well spatial light modulators and their applications in projection/head-mounted displays, optical data processing, and adaptive optics. He is currently an Associate Professor at the Electro-Optics Engineering Department, Ben-Gurion University, Negev, Beer-Sheva, Israel. He also heads the OPTO-ULSI Laboratory at Holon Academic Institute of Technology, Holon, Israel. He is currently conducting research on liquid crystal devices, plasmonics, CMOS-ultra-large-scale integration (ULSI) technology, and image processing for applications in smart goggle/head-mounted display devices, low-vision aids, face recognition techniques, and beam-steering devices. Dr. Efron is a Fellow of the Optical Society of America.
Host: Prof. B. Keith Jenkins
Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248
Audiences: Everyone Is Invited
Contact: Talyia Veal
