Extending the pi-Conjugation Length of Soluble Semiconducting Polymers to Effect Efficient Charge Transport

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TECHNICAL ABSTRACTRealization of polymer architectures with well-defined dimensions and functions is one of the current research challenges in the field of organic semiconducting materials. Materials that meet requisite performance targets and will markedly reduce overall process complexity are essential. The proposal focusses on the design, synthesis and characterization of pi-conjugated polymers having the following characteristics: a low bandgap, a low HOMO level, and effective pi-pi interactions. The aim is to define a strategy for the effective extension of the conjugation length of polymers having electro-optic characteristics. The materials are expected to exhibit enhanced field-effect induced charge transport and photovoltaic properties, features that an imperative for the successful introduction of robust and reliable polymer based devices.Specifically, the PI will (1) investigate the effectiveness of the vinylene linkage to extend the conjugation length of targeted polymers, (2) investigate alternative alkyl side chains and their ability to solubilize targeted polymers in common organic solvents, allowing for solution processing, (3) synthesize alternative D-A architectures, (4) perform requisite physical characterization of the targeted materials, (5) fabricate field effect transistor and photovoltaic devices to evaluate the impact of the approach. Through the studies defined above, it is anticipated that identification of key, synthetically accessible structural features will provide for an extension of the pi-conjugation length of semiconducting polymers with requisite characteristics that will allow for orientation and alignment that are favorable for charge transport. These studies will identify means to achieve energy levels and bandgaps that not only afford desired electro-optic performance, but also support robust and reliable devices.NON-TECHNICAL ABSTRACTConjugated polymeric materials in general, and polymer semiconductors in particular, are of broad interest because of the wide range of possible applications including organic light-emitting diodes (OLED), organic field effect transistors (OFET), photovoltaic devices (PV), electro-optic shutters, printed antennas, plastic-based actuators, and signal switches. Further, polymers offer compatibility with high through-put, low cost processing techniques. The proposed research program will provide essential insight needed for the development and deployment of advanced polymer materials for electro-optic device applications having significant societal impact, examples of which are described above. Students participating in this effort will gain invaluable experience working in a multidisciplinary program. This approach will allow them to experience a broad education and to acquire a sound knowledge base in the area of polymer science and engineering coupled with an appreciation of the contributions of other disciplines. The research program will be integrated with undergraduate and graduate students working in teams to further the objectives of the proposal. Additionally, opportunities will be sought for high school students to participate in these teams. Outreach activities will target the local very diverse community, and both the PI and students will participate. Through these activities, public understanding of STEM will be enhanced, thereby positively influencing a diverse future generation of students to enter STEM fields.