Pyromellitic Diimide (PyDI)-Based Molecular and Polymeric Electron-Transporting Semiconductors

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"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."TECHNICAL SUMMARY: Pyromellitic (benzenetetracarboxylic) diimides (PyDIs) are best known as segments of highly insulating polyimide dielectrics This proposal is to build on the transformative concept that a simple PyDI structure is a sufficiently conjugated core for the construction of electron-carrying organic semiconductors for polymer-based electronics and energy transducers. This structure is more readily available than the higher rylenes already investigated, is highly transparent and chemically stable, and leads to processable and electronically tunable derivatives. While numerous small-molecule and polymeric hole-carrying (p-channel) semiconductors have been developed, the list of electron-carrying (n-channel) alternatives, while growing, remains smaller. There are particularly few examples of processable n-channel semiconductors. Most conjugated cores for n-semiconductors have very high melting points. Those few that are solution processable require extensive syntheses. This proposal develops the counterintuitive idea that PyDIs can function as molecular and polymeric semiconductors in transistors and other devices. The PI has already shown that PyDI semiconductors can have electron mobilities 0.1 cm2/Vs. Transistors made from PyDI derivatives are operable in air and have very high on/off ratios. This proposal is to perform a systematic study of N and 3,6-C substitution on PyDIs, develop solution processability, and extend these structures into printable polymers. Fundamental issues to be addressed include the electron energy level tunability through substitution, relative merit of PyDI and naphthalenetetracarboxylic diimides, preservation of solid state packing in processable solids, comparison of conjugated and nonconjugated substituents and polymer linkages, reliability of molecular solids versus polymers, and enhanced viscosities of polymer solutions for printing. The morphology and crystal structures will be determined for a wide range of derivatives, as will the orbital energy levels relative to other materials in which the PyDIs might be blended or with which they might share interfaces.NONTECHNICAL SUMMARY: New organic and polymeric materials, though based on a structure generally associated with insulators, will in this case further opportunities for organic based circuit, solar cell, capacitor, and thermoelectric technologies. They will be utilized in modules for undergraduate and high school laboratory course teaching. One particular course is being developed specifically to utilize organic electronic devices, and will be transferred to predominantly undergraduate institutions such as Drew University and University of Maryland-Baltimore County, and Anne Arundel High School. The modules will also be presented to high school teacher workshops that include a diverse mix of attendees from urban school districts. Mentoring of graduate and undergraduate students, including joint and visiting minority students from Howard University, will be emphasized.