Phase segregated inorganic heterstructures for low cost, high efficiency photovoltaics

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0930098BentThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).SummaryIntellectual Merits: The development of sustainable energy solutions that will meet the needs of a growing world population, while reducing greenhouse gas emissions, will rely in large part on renewable energy sources. With a global radiation flux of 174,000 TW, solar energy is a renewable resource that has the potential to provide more than enough energy to power the world. However, current solar cell designs are too expensive to be adopted for large scale application. Hence, new materials and designs for photovoltaics are urgently needed. One design that is of growing interest is a nano- or microscale heterojunction design with interdigitated semiconductor layers, in which the light absorption path length can be decoupled from the carrier diffusion path to the device junction in order to maximize the device efficiency. However, the difficulty of making such nano- or microstructures using any currently available method will drive the cost of the solar cells up, likely negating any increase in efficiency. This project proposes to investigate a novel fabrication technique and materials system that will allow nanostructured or microstructured designs for solar energy conversion to be made at lower cost. Specifically, fundamental studies into a guided self-assembly process in which selected inorganic mixtures are induced to self-organize into the desired heterostructures will be conducted. A thin film of a multicomponent mixture will be deposited that will be converted during growth or through a second simple thermal or chemical process to a three-dimensional nanostructure via self-assembly. This study will investigate the choice of materials system that will form two semiconductors of opposite polarity with optimal band and interfacial properties and will explore methods to guide the assembly process into the desired photovoltaic structure. It is expected that fundamental advances to the understanding of guided self-assembly in materials science will be made. In addition, the research has significant potential for influencing not just the photovoltaic field but also a broad range of nanoscience studies. Broader Impacts: The research promises to introduce a new approach to making photovoltaics which, if successful, could have a significant worldwide impact. Our approach has the potential to provide high-efficiency solar cells at a cost comparable to cheap window glass coating, allowing solar electricity to be competitive with that produced from coal and leading to significant reduction in greenhouse gas emissions. In addition, the proposed program will achieve broader impacts in several key ways: (1) Teaching and training; (2) Broadening participation of underrepresented groups; (3) Disseminating research results broadly to enhance science and technological understanding; (4) Outreach to the public. The proposed project will continue building upon the important foundation of training both graduate and undergraduate students carried out by the PIs. Currently many of the students in their research groups are minority or female. Moreover, the PIs propose to engage a high school teacher from local minority-serving schools on this project in the laboratory for two summers through the Summer Program of Professional Development.