CAS: New BODIPYs That Are Capable to Form Coordination-bonded Panchromatic Arrays For Light-harvesting

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With the support of the Chemical Structure, Dynamics, and Mechanisms B (CSDM-B) Program in the Division of Chemistry, Professor Victor Nemykin of the University of Tennessee is studying several new classes of molecules, that have the potential to replace currently used carbon nanomaterials as electron acceptors in the light-harvesting modules of organic photovoltaics (OPV) devices. Naturally occurring porphyrins and their derivatives are well-known "pigments of life," which are responsible for light-harvesting, oxygen transfer, the catalytic transformation of biological substrates, and many other functions. Porphyrin derivatives perform best in Dye-Sensitized Solar Cell (DSSC) modules. Although fullerene, its derivatives, and the other nano-carbon materials are typically thought of as electron-acceptors for donor-acceptor assemblies, they suffer several limitations. First, they are not bright chromophores, especially for the low-energy range of the solar spectrum. Second, over the years, it has become clear that they significantly limit the mechanical flexibility, stability, and overall performance of OPV cells. Finally, fullerene and its derivatives are still very expensive when the overall cost of the OPV device is considered. In order to address the major deficiencies of fullerenes and their derivatives, Professor Nemykin’s team is planning to prepare a broad range of bright porphyrin-related chromophores with a first reduction potential that is energetically close to that of fullerenes (electron-donors) paired with a set of non-fullerene, BODIPY-like electron acceptors. They hope that these new molecules will outperform currently used nano-carbon materials as electron acceptors in OPV devices to eventually allow for the development of new, economically viable light-harvesting modules for solar cells. This project will help to train next generation research scientists through the cross-disciplinary nature of the research, with exposure to inorganic, organometallic and theoretical chemistry, as well significant application of spectroscopy. In an effort to reduce the manufacturing cost of OPV solar cells, researchers have been developing new OPV technologies that adopt room temperature solution-based fabrication techniques. The resulting solar cells also have many potential advantages in terms of mechanical properties (flexible solar cells) and broad platform deployment (paint-on solar cells). In pursuit of the preparation of the artificial light-harvesting materials that would be as effective as the natural photosystem, a variety of synthetic dyes such as porphyrins, phthalocyanines, and BODIPYs been studied in the last decade, with the best, porphyrin-based, DSSC system providing ~13.5% efficiency in the solar light-to-electricity conversion. In this project, the principal investigator’s team will prepare, characterize, and investigate a set of new panchromatic supramolecular assemblies formed using coordinating bonds between electron-donating porphyrinoids and new electron-accepting chromophores. In particular, specific emphasis will be on the design, preparation, and characterization of the new electron-deficient chromophores that can outperform and substitute nano-carbon materials as electron-acceptors. These new chromophores will belong to the electron-deficient BODIPY family including aza-BODIPYs, and MB-DIPYs. Photo-induced electron-transfer processes between porphyrinoids (electron-donors) and new electron-acceptors (BODIPYs, aza-BODIPYs, and MB-DIPYs) in supramolecular assemblies will be studied by an array of the experimental and theoretical methods to characterize these systems thoroughly and identify optimal non-fullerene donor-acceptor systems for eventual deployment in OPV devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.