(678a) Organic Electronics: New Materials and Strategies for High Performance Organic Light Emitting Diodes, Thin Film Transistors and Photovoltaic Cells

Many advances have recently been made in the development of organic electronics that exploit the wide range of electronic, optoelectronic, and photonic properties of organic and conjugated polymer semiconductors. Organic light-emitting diodes (OLEDs) for full color displays are being commercialized by many companies and OLED-based display products are appearing in cell phones, automobile dashboards, digital cameras, etc. OLEDs are also showing promise for solid state lighting applications. Photovoltaic cells based on conjugated polymers and organic semiconductors are also of much research interest since they offer a promising low-cost approach to efficient solar power generation. Sunlight (AM 1.5) illuminated polymer photovoltaic cells with power conversion efficiencies of about 3-5 % have been demonstrated. Ultrasensitive photodetectors for visible to ultraviolet radiation have been fabricated from semiconducting polymers. Great strides have also been made in developing organic and polymer thin film transistors for potential applications in low-cost integrated circuits for logic, memory and other functions in microelectronic systems. Applications of such thin film transistors in active-matrix displays, smart cards, identification tags, sensors, and other systems are envisioned and are being explored. To improve the performance of all of these organic electronic devices and accelerate the emerging era of plastic electronics, new readily processable and thermally robust, emissive and high charge carrier mobility materials are needed for developing the next generation high-performance blue, green, red, and white OLEDs. Conjugated polymer semiconductors that have high charge carrier mobilities, solution processability, and air stability are also of enormous interest for applications in other areas of organic electronics, particularly thin film transistors and photovoltaic cells. In this talk, we will describe recent work on organic electronics in our laboratory, including light emitting diodes for displays and solid state lighting, photovoltaic cells, and thin film transistors. Several examples will be used to illustrate an approach in the molecular engineering of materials and devices: polymers and oligomers for high-efficiency blue, green, red, and white light-emitting diodes; air-stable high mobility n-channel polymer field effect transistors and the molecular weight and temperature dependence of electron mobility; ambipolar thin film transistors from binary blends of polymer semiconductors; donor-acceptor with unusual temperature-dependence of carrier mobility copolymers for thin film transistors and photovoltaic cells; and the synthesis, self-assembly, nanoscale morphology, and ambipolar charge transport in a novel class of conjugated polymer nanowires. One of our central findings is that the self-assembled supramolecular structure or morphology of the polymer semiconductors can have a profound, even dominant, influence on their properties and the performance of devices.