Self-assembly of redox molecules

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Nature of the work to be done: Our research program uses organic synthesis to design novel organic semiconductors that could find applications in photovoltaics, transistors, diodes or batteries with the potential of printable, flexible, lightweight and economical electronics. The primary goal of our program is to synthesize new organic building blocks that can carry charge; in addition, we design our new molecules to promote self-assembly to optimize the ability to move charges. The research proposal targets specifically organic photovoltaics (OPVs) applications by using light-absorbing molecules, porphyrinoids, and charge carrying molecules, quinones. Essential to the operation of the organic semiconductors in devices is the ability to carry charges over large distances. Our proposal suggests liquid crystalline phases, which are intermediate phases between liquids and crystals, enable the materials to maintain flexibility yet take advantage of the high charge carrying ability found in crystals. By exploiting supramolecular chemistry principles, we can induce molecules to self-assemble into soft phases, such as liquid crystals. Our synthetic design involves the synthesis of a rigid core that is surrounded by flexible chains that impart the flexibility characteristics. The balance of the electronic properties and size of the rigid core with the length and composition of the flexible chains can lead to liquid crystalline phases. The organized materials force the rigid cores to overlap, which is critical for the mixing of orbitals that allow for intermolecular charge transport. Our inspiration is derived from a simplistic view of the early events in photosynthesis. Specifically, nature uses porphyrinoids for light harvesting and quinones as ‘electron’ shuttles under exquisite control and organization. We propose to enhance the light harvesting properties of porphyrin components by synthetic means and we have already demonstrated successful self-assembly with these modified porphyrins. For the quinones, electron acceptor, building blocks we propose several new cores that show promising electron affinities that will be furnished with self-assembling functionality. Why and to whom the research is important: By combining new organic charge carrying building blocks with self-assembling properties, we are targeting a disruptive step, as opposed to incremental, in new organic materials that can migrate charges (either holes or electrons) efficiently, which will impact all of the organic semiconductor applications described above. Exploiting the proposed materials will have a significant impact on OPV applications, such that this work could enable flexible, economical, large area printing of solar cells, which are significant roadblocks to large-scale solar energy adoption. Furthermore, the new syntheses will be a benefit to the organic chemists, the novel electronic and optical properties will be insightful for the materials chemist and the self-assembly is key to build better understanding of intermolecular interactions for the supramolecular chemistry community. Anticipated outcomes: First, the production of self-assembling materials that shuttle charges efficiently could be the step needed for organic semiconductors to flourish. Second, students will be trained as scientists and learn how to communicate with diverse audiences and become leaders to tackle unforeseen challenges. How the research field and Canada will benefit: Since the outcomes of the research could provide an abrupt change in the efficiency of organic compounds to carry charge, Canada could be an emerging leader in organic electronics, particularly photovoltaics devices that are inexpensive, printable and flexible.