New conjugated polymers for organic electronics: Synthesis, properties, and applications

Organic and conjugated polymer semiconductors are of wide interest for applications in electronic and optoelectronic devices, such as organic light emitting diodes (OLEDs), photovoltaic cells, and thin film field-effect transistors. The design and synthesis of readily processible new conjugated polymers with improved multifunctional properties and an understanding of the underlying structure-property relationships are essential for developing the next generation of high-performance organic electronic devices. The goal of this research is to design and synthesize new polymer and organic semiconductors, elucidate the structure-property relationships that govern their electronic and optoelectronic properties, and to explore their applications in OLEDs and thin film transistors.; New 100 % regioregular poly(4-alkylquinoline)s were synthesized by self-condensation polymerization and found to form liquid crystalline mesophases and to be useful semiconductors for OLEDs and thin film transistors. The poly(4-alkylquinoline)s undergo pi-stacking driven self-assembly into solid state nanostructures exemplified by crystalline nanowires of binary blends of poly(4-hexylquinoline) and regioregular poly (3-hexylthiophene). These nanowires showed ambipolar charge transport with high field-effect electron (0.004 cm2/Vs) and hole (0.012 cm2/Vs) mobilities.; New conjugated polymer and oligomer semiconductors with donor-acceptor (D-A) architectures were designed, synthesized and successfully explored in electronic devices. The effects of the donor and acceptor moieties on the electronic and optical properties of polymer semiconductors were investigated. D-A copolymers of quinoxaline or dibenzo[a,c]phenazine electron-accepting moiety with 9,9-dioctylfluorene were found to be efficient blue-emitting materials for OLEDs. D-A copolymer semiconductors with thienopyrazine acceptor and thiophene donor were shown to combine small band gaps (1.1-1.6 eV) and broad visible-to-near infrared absorption with high field-effect charge carrier mobility. Highly reversible electrochemical reductions and unusually high electron affinities (3.6-3.9 eV) were realized in D-A copolymer semiconductors incorporating pyrazinoquinoxaline as the acceptor. Phenoxazine-based D-A molecules were synthesized and shown to be highly emissive materials for developing efficient blue, green, yellow, and red OLEDs. Related conjugated polyphenoxazines proved to be useful in p-channel field-effect transistors.