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<a href="http://web.mit.edu/mitei/" border="0" > <img src="http://web.mit.edu/miteicomm/announcements/mitei-series-banner.jpg" alt="MITEI: MIT Energy Initiative" style="padding-top:5px;"/></a>
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<h1><strong>Predictive Defect Engineering for Scalable Photovoltaics at $1/Wp</strong></h1>
<h1>Tonio Buonassisi</h1>
<h2>Photovoltaics Research Laboratory<br/>
Department of Mechanical Engineering and Laboratory for Manufacturing Productivity, MIT</i>
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<h3>Tuesday, November 9</h3>
<h3>4:15 PM</h3>
<i>Refreshments to follow</i><br/>
<h3><a href="http://whereis.mit.edu/?go=66"> Room 66-110 </a></h3>
<strong>Abstract</strong>
<p>At $1 per peak watt installed cost, solar photovoltaics is projected to be cost-competitive with traditional fossil fuels in many markets across the United States. To meet this cost target and ensure scalable production, thin low-cost materials must be used. Herein lies an important trade-off: Low-cost materials are typically defect-rich, and defects impede electronic transport and photoconversion efficiency. Since efficiency and cost are inversely related, defect-rich materials have until recently resulted in poor-quality, economically uncompetitive solar cells.</p>
<p>In this presentation, we explore a path towards low-cost, high-performance, and scalable photovoltaic absorbers. We introduce the concept of "defect engineering," the science of controlling defects to engineer desired material properties. We review recent successful applications of defect-engineering technologies to traditional ingot multicrystalline silicon that have led to cell efficiencies above 16%. Accurate identification of performance-limiting defects requires multiscale characterization, evaluating cm-size devices and probing down to the nanometer scale for defect recognition. We will review recent advances in macroscopic CCD-based PV device characterization tools, and elucidate how these can be coupled to synchrotron-based nanoprobe techniques to characterize chemical natures and distributions of performance-limiting defects less than 20 nm in diameter. Once the natures and underlying physical behavior of these defects are known, an opportunity exists to engineer these defects - aided by predictive modeling - to enhance solar cell performance.</p>
<p>We then consider candidate PV materials with cost-reduction and scaling potential to support $1/Wp installed costs, yet which are currently defect-limited: Hyperdoped silicon, with a modified silicon band structure and potential to exceed the Shockley-Queisser efficiency limit; tin-sulfide (SnS), a potential Earth-abundant replacement for CIGS; and cuprous oxide (Cu2O), a potential silicon superstrate for high-efficiency heterojunction devices.</p>
<p><strong>About the speaker</strong></p>
<p> Tonio Buonassisi, assistant professor of Mechanical Engineering at the Massachusetts Institute of Technology, heads an interdisciplinary laboratory focused on photovoltaics (solar energy conversion into electricity). Prof. Buonassisi completed his Ph.D. at UC Berkeley, with research at the Fraunhofer Institute for Solar Energy Systems and the Max-Planck-Institute for Microstructure Physics. Following his Ph.D., Prof. Buonassisi became a crystal growth research scientist at Evergreen Solar, Inc., where he spearheaded efforts to improve solar cell efficiency and yield, and helped to develop the Quad furnace platform. Aside from teaching classes focused on PV technology, Prof. Buonassisi is an author of 65 journal, conference, and workshop articles focused on PV, and has delivered over 51 invited talks and plenary/oral presentations on his work throughout the world. Prof. Buonassisi's research has resulted in several industrial collaborations and a start-up company. His work has been honored with awards including the European Materials Research Society Young Scientist Presentation Award, the German Academic Exchange Service (DAAD) Graduate Research Fellowship, and the National Renewable Energy Laboratory Graduate Student Award.</p>
<p><strong>The Seminar Series is made possible with the generous support of IHS-CERA</strong></p>
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