SOLAR: Hybrid Semiconductors: Overcoming the Excitonic Bottleneck in Low Cost Solar Cells

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TECHNICAL SUMMARY:Meeting the energy needs of the world's growing population in an environmentally sustainable way is among the most important scientific challenges facing society today. This research project seeks transformative breakthroughs in the low-cost approach to efficient harvesting and conversion of solar energy into electricity by pursuing the following question: can an entirely new class of semiconductors be invented that generates delocalized excitonic species upon photoexcitation, presents new strategies for better harvesting of solar energy, and offers enhanced charge transport and collection in photovoltaic devices? Toward these ends, the project brings together investigators in chemistry (Prezhdo, Jenekhe, Luscombe), mathematics (Chen), and materials science (Cao, Schlaf, Luscombe, Jenekhe) to explore molecular level synthesis, characterization of electronic structure, and charge transport of a novel class of hybrid semiconductors for applications in low-cost solar cells. The planned research will: (1) Design and synthesize an entirely novel class of semiconductors, consisting of organic-organic and organic-inorganic hybrid semiconductors with engineered electronic, optical, and charge transport properties; (2) Determine the detailed electronic structure of these novel hybrid materials by photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES); (3) Determine the optical and charge transport properties of the organic-organic and organic-inorganic hybrid semiconductors; (4) Develop a new mathematical approach to understanding the separation, annihilation, and transport of charges in hybrid semiconductors and associated photovoltaic devices; and (5) Explore the new hybrid semiconductors in solar cells. NON-TECHNICAL SUMMARY:The sun represents the most abundant potential source of pollution-free energy on earth. However, energy from current photovoltaic technologies is too expensive compared with that from fossil fuels. Novel semiconductor materials and devices that could potentially revolutionize solar energy conversion technologies, making them cost-competitive with fossil fuels, are needed. This project brings together several scientists with research expertise in chemistry, materials science, and mathematics to develop the basic knowledge needed for inventing new semiconductors and new photovoltaic devices for more efficient conversion of sunlight into electricity. Results from the project will lead to new generations of low-cost solar cells with high conversion efficiency and thereby contribute to addressing the energy and environmental challenges faced by society. The project also provides excellent opportunities for the training of scientists and engineers, including women and minorities, in the highly interdisciplinary fields of energy science and technologies, which require knowledge of chemistry, physics, materials science, mathematics, and engineering. New courses on solar energy materials, devices, and technologies, will be developed and taught at the upper undergraduate and graduate student levels. The project's senior investigators have a longstanding history of involvement of undergraduate, women, and minority students in their individual research programs. These efforts will be continued and expanded through this group project. The project's investigators have many research collaborations with scientists in Japan, China, Germany, Belgium, South Korea, Taiwan, Switzerland, Poland, UK, and Ukraine in the general areas of energy and electronics; they have hosted visits by senior scientists and students from some of these countries. This project will strengthen those international collaborations.