Implementation of Intermediate-Band Solar Cells using Multi-Band Semiconductors

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0932905WuThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).SummaryThe project is aimed at the full demonstration of an intermediate-band solar cell based on the recently discovered multi-band semiconductor alloy AlyGa1-yAs1-xNx. The research to be undertaken targets fundamental questions in photovoltaics science and technology. Can the Shockley-Queisser limit of photovoltaic efficiency in a single p-n junction be overcome? What new paradigms in solar-cell operation can be realized in a single-phase material through electronic structure engineering? The broader objectives of this program are to train undergraduate and graduate students as well as postdoctoral researchers in a collaborative environment, to transfer research innovations and concepts in energy science and policy to the classroom, and to engage the surrounding community, specifically elementary school children, in discussions and learning around energy sustainability and the role of technology. Intellectual Merit. If successful, this research program will lead to the highest ever photovoltaic efficiency, exceeding 35%, in single-junction, single-phase solar cells. Such an achievement would produce significant advancements in the understanding of solar cells based on intermediate bands - a promising device architecture that has been predicted but not yet demonstrated to yield high energy conversion efficiency, hence, potentially at much lower cost than highly efficient multi-junction solar cells. Demonstration of an intermediate-band solar cell using the multi-band semiconductor AlyGa1-yAs1-xNx epitaxially integrated into a conventional p-n junction will promote innovations in semiconductor thin-film growth and device processing. New knowledge concerning the materials physics of the multi-band semiconductors will be gained. The interaction of such a multi-band system with broad-spectrum photons has not been fully characterized and understood. Therefore, a significant portion of the proposed activities will be devoted to elucidating the photo-physics and thermodynamics of charge carriers in this novel materials system.Broader Impacts. The transformation of sunlight into electrical energy using photovoltaics has captured the imagination of not only scientists, engineers and technologists but also the public at large. Solar cell research provides exciting opportunities to engage future innovators in energy science and technology at all levels. The proposed research and education program at U.C. Berkeley will provide invaluable training and opportunities for learning to students at all stages, from elementary school to the postdoctoral level, in the San Francisco Bay Area. As an emerging industry, energy technology will experience tremendous growth, making the infusion of diversity now a critical action. The proposed outreach activities will be targeted to promoting diversity in the energy sector by the training and mentoring of scholars from diverse backgrounds.