Shining a new light on molecular biexcitonic processes: novel molecules and DNA origami

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In the fight against climate change, renewable energy is our strongest ally. Solar energy is an abundant natural resource, especially in Saskatchewan, where we receive an average of 2,264 hours of sunshine per year. A standard industrially-produced solar cell achieves a light-to-electrical output efficiency of only 18-22%, and so much of the light is not absorbed or absorbed only to be dissipated as heat. New materials that rely on biexcitonic energy-transfer processes have the potential to revolutionize the efficiency with which light is captured and transported in solar-harvesting devices. This proposal addresses this transformative opportunity. We will develop a new class of materials, based on azulenes, that maximize solar-radiation capture, as photons from the entire solar spectrum can trigger biexcitonic processes. Excitations, or excitons, created by low-energy photons can combine to produce higher-energy excitons, while each high-energy exciton can split to produce two lower-energy excitons. This singlet-fission (SF) process can increase power-conversion efficiencies as higher electrical currents result for each photon absorbed. However, few molecules fulfill the strict energy-level requirements, and interact with their neighbouring molecules with the appropriate strength, necessary for SF to occur. Our novel approach is to develop a totally new class of azulene-derived molecules in which efficient SF occurs from unusually-high energy levels. We will visualize and quantify the myriad energy-transfer pathways involved in their biexcitonic processes using ultrafast optical spectroscopy techniques. We will also control interactions between molecules by binding them to nano-scale DNA-origami structures, thus constraining their relative positions and precisely tuning their interactions. Through this dual approach, my research group will markedly extend our knowledge of molecules known to exhibit efficient biexcitonic processes and will develop robust, high-performance materials based upon these processes. This research will drastically improve the efficiency of light-harvesting devices and spawn new technologies, such as new medical-imaging modalities, DNA-based drug delivery vehicles, and ultrasensitive environmental detectors. As this approach is based on azulenes, a natural extension is to detect azulene-like defects in graphene, which are a stumbling block in bringing to fruition many graphene-based innovations sought by the electronics industry. The results will help to position Canada as an influential force in renewable energy technologies, and the highly-qualified personnel working on this research will enter the Canadian labour market with transferable next-generation skills in science and technology. Through supportive and proactive mentorship, my graduates will carry forward values of equity, diversity, and inclusivity. Their training will empower them with the knowledge and tools to continue innovating towards a bright future.