CAREER: Search for Ideal Polymers for Highly Efficient Organic Solar Cells

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TECHNICAL SUMMARYThe central theme of this 5-year integrated career plan is to advance the research and education in the area of novel polymers for highly efficient photovoltaic cells. Built upon the PI?s previous successes in the design, synthesis and characterization of new polymers for photovoltaic applications, this CAREER proposal 1) summarizes the design criteria for ?ideal? polymers to further improve the efficiency of polymer PV devices, 2) proposes a design motif based on the PI?s previous systematic study, and 3) will conduct an in-depth and systematic study of selected polymers to test and enrich the proposed design motif. A weak donor ? strong acceptor modular approach to construct copolymers will be used with the intention of lowering the band gap and simultaneously tuning the HOMO/LUMO energy levels. The donor moieties contain extended ð conjugation, which will promote the ð?ð interaction between different polymer chains to improve the charge carrier mobility. A series of acceptors with different electron-withdrawing ability will also be prepared as the other building block for the polymers. A library of new polymers with tunable band gaps and energy levels will be explored. In addition, the PI will start a comprehensive device optimization including annealing, applying additives, and employing interfacial layer. Furthermore, the PI will carry on fundamental studies of exciton behaviors in these structurally related polymers (e.g. exciton dissociation, recombination and diffusion), which should provide more insightful information about why certain polymers are better than others. Finally, the elucidated mechanism will assist future design of new materials. The summarized design criteria of ideal polymers for solar cells, in particular, the proposed design motif, will expedite the discovery of new and better polymeric materials through rational design. New chemistry and novel polymeric materials will be developed. This research can potentially lead to highly efficient, affordable solar cells with low manufacturing cost, whose impact would be tremendous to the fast-growing market of solar cells. NON-TECHNICAL SUMMARYThe interdisciplinary nature of this research on polymer solar cells will impact a wider range of disciplines, including synthetic organic and polymer chemistry, physical chemistry, materials sciences and engineering. Integration of education and outreach with research is the key feature of the proposed work. Underrepresented groups, specifically women and minorities, are particularly encouraged to participate in the proposed research through aforementioned programs. Participants will have a unique opportunity to involve in many key aspects of the development of polymer based solar cells. Students will receive interdisciplinary training, from organic and polymeric materials development and characterization, to device fabrication, and evaluation. Through partnership with Climate LEAP and creating new programs for Science 360, the PI will produce multimedia content and conduct energy education presentations and activities, so as to reach out more high school students and teachers, and the general public. All these activities will increase the public awareness of current serious energy issues, and direct public attention to a sustainable future powered by renewable (solar) energies.