SusChEM: Materials and Architectures for High Efficiency Organic Photovoltaics

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PI: Mark E ThompsonProposal Number: 1511757The sun represents the most abundant potential source of sustainable energy on earth. Solar cells that use light-absorbing organic polymers to convert light to electricity ? organic photovoltaic (OPV) devices - offer a potentially low-cost route for renewable electricity production. However, in order to achieve parity with other solar photovoltaic technologies, organic solar cells must increase their power conversion efficiency past the current 10.5% world record. One reason for this low efficiency is that OPV devices do not harness the light energy in the infra-red range of the solar spectrum, which is beyond the visible range of light. The overall goal of this project is to design new light absorption materials for OPV that simultaneously increase infra-red light absorption and improve the voltage output, leading to a potentially significant incremental increase in solar energy conversion efficiency. Through this research, fundamental scientific understanding on how to more rationally align the energy conversion processes within OPV devices will be also gained. As part of the educational activities associated with this project, students from a community college in Los Angeles will participate in summer research on solar energy, hosted through the laboratory of the principal investigator.The overall goal of the proposed research is to enhance the performance of organic photovoltaic (OPV) devices through the development of new materials and device architectures that extend light absorption and conversion into the near infra-red (near-IR) portion of the solar spectrum, and concurrently increase the open circuit voltage towards its theoretical limit. Towards this end, small molecules that absorb strongly into the 950-1000 nm range will be used as part of single and multiple sensitization strategies to achieve broadband absorption in the visible to near-IR spectral range. Furthermore, intramolecular symmetry breaking charge transfer materials, which contain both electron donors and acceptors, will be designed to narrow the offset between the energies of the charge transfer state, exciton, and the open-circuit voltage. In this context, the research plan has two primary objectives that will be carried out interactively. The first objective is to prepare and characterize the photophysical properties of new materials, and then second objective to develop novel structures that utilize these new materials in OPV devices. Theoretical models will be used to predict absorption energies for a wide range of cyanine-like dyes for near-IR, and from these studies, the most promising small molecule materials will be synthesized, characterized by photophysical methods, and then tested in OPV devices. Synthetic and photophysical characterization studies will also be carried out to determine the parameters that control symmetry breaking charge transfer (SBCT) in strongly absorbing materials. This fundamental understanding will be used to design OPV device architectures to accommodate these SCBT materials. The device physics of OPV devices containing SCBT materials will be then characterized to understand the phenomena that could lead to increased open circuit voltage. Finally, all dye targets will be designed to serve as suitable ligands for preparation of zinc-dye complexes. These new zinc complexes are expected to promote symmetry breaking charge transfer, making it possible to simultaneously increase near-IR spectral response and increase open circuit voltage. If successful, these new OPV materials will improve solar energy conversion efficiency through synergistic design of light absorption and charge transfer processes.