CAREER: Strain Balanced Quantum Dots for High Concentration Solar Photovoltaics

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Technical: The research objective of this CAREER award is to address the fundamental materials research need for future high-efficiency solar cells. While existing studies suggest benefits of nanomaterials in enhancing solar cell efficiency, there remains a significant amount of fundamental materials research necessary for practical implementation. Examples include selection of the appropriate quantum confined materials system, study of the growth and incorporation mechanisms of epitaxial nanostructures into solar devices, and relation of the optical and electrical results to theoretical predictions. Additionally, high concentration photovoltaic systems must operate under elevated operating temperatures, thus degradation mechanisms in nanomaterials is a critical issue. The project is designed to investigate the following materials based topics: 1) vapor phase epitaxial growth and characterization of multi-layer stacks of group III-V quantum dots (QD) using a dot-barrier strain balancing technique; 2) analysis and demonstration of true wavefunction overlap and miniband formation in quantum dot solar cells using both optical and electrical characterization, and 3) study of degradation mechanisms in QD cells under variable environmental conditions. In all of the above, emphasis is placed on understanding the interplay between high quality vapor phase epitaxial growth of the quantum dot, nanostructured solar cell optical and electrical characterization, fundamental quantum mechanical predictions and subsequent carrier transport mechanisms. This project leverages existing activities in nanomaterials and solar cell development at the Rochester Institute of Technology NanoPower Research Labs and NASA Glenn Research Center.Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance. The success of the project is expected to have impacts on the further advancement of nanostructured materials for solar energy harvesting and, in general, nanoscience and nanotechnology. The research and education activities of the project are integrated. This project trains Ph.D. and undergraduate students in the emerging fields of nanotechnology and photovoltaics. Students have the opportunity to spend the summer at NASA Glenn Research Center's Photovoltaics and Power Technologies Branch, learning valuable skills involving nano-material growth and state-of-the-art solar cell characterization techniques. The knowledge gained from the research can be directly incorporated into developing both undergraduate and graduate level courses in next generation photovoltaics, thus involving an even lager body of students in renewable energy topics. Beyond the teaching aspect, the results of this project are planned to be disseminated through both publication and collaboration with companies such as Emcore Photovoltaics and Spectrolab.