n-Type and Ambipolar Polymer Semiconductors

University Of Washington, Seattle WA

Investigators

Abstract

TECHNICAL SUMMARY: The performance of all current polymer semiconductor devices, such as thin film transistors, photovoltaic cells, light-emitting transistors, light-emitting diodes, and photodetectors, is limited primarily by the charge carrier mobilities of current materials. A fundamental challenge to improving the performance of all these devices and moving them towards practical systems applications is thus to achieve higher charge carrier mobilities. Furthermore, investigation of n-type and ambipolar polymer semiconductors has lagged far behind p-type polymer semiconductors. In this project, fundamental insights into the structural factors that govern high-mobility electron and ambipolar charge transport in polymer semiconductors are sought. Novel organic solvent-soluble n-type polymer semiconductors will be synthesized and studied, including poly(anthrazoline)s, poly(pyrazinoquinoxalines)s, and ladder poly(pyrazinoquinoxaline)s whereas poly(bisindoloquinoline)s and other donor-acceptor copolymers will be explored as ambipolar semiconductors. The solid state morphology and molecular packing in thin films and nanowires of polymer semiconductors will be characterized by electron microscopy and X-ray diffraction techniques. Charge carrier mobilities of polymer semiconductor thin films and nanowires will be measured by using the field-effect transistor as a platform. The most promising materials will be explored in high-performance field-effect transistors, complementary inverters, and photovoltaic cells. Polymer semiconductors that combine air-stability with high electron mobility or ambipolar transport with high carrier mobilities will be useful for developing all-plastic complementary integrated circuits for logic and memory functions and for improving the efficiency of plastic solar cells. Indeed, the realization of ambipolar polymers with high carrier mobilities could revolutionize the design of organic solar cells, light-emitting transistors, and all organic electronic devices and systems. NON-TECHNICAL SUMMARY: Electronic devices based on organic and polymer semiconductors, termed plastic electronics, are beginning to find many applications such as displays in cell phones, digital cameras, and car dashboards. Plastic electronics are also being tested for uses in applications ranging from flat-panel displays for computer and television screens, solid-state lighting, chemical- and bio-sensors, to low cost solar cells. This project will develop the basic knowledge for improving the performance of polymer semiconductors. Results from the project will lead to new materials and manufacturing technologies for plastic electronics and related applications in information technologies and renewable power sources. The project provides excellent opportunities for the training of scientists and engineers, including women and minorities, in the emerging interdisciplinary field of plastic electronics, which requires knowledge of chemistry, physics, materials science, and engineering. The principal investigator?s laboratory has several research collaborations with scientists in Greece, South Korea, Taiwan, Switzerland, and Japan in the general area of plastic electronics; it has hosted visits by senior scientists and students from some of these countries. This project will strengthen those international collaborations.