Opportunities and Challenges in the Field of Semiconducting (conjugated) Polymers

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

TECHNICAL SUMMARY The research will focus on two aspects of current opportunities and challenges in the field of conducting polymers: A. Interdisciplinary research, involving polymer science, physics and device science, will improve the efficiency and brightness of the emission from Light-Emitting Field Effect transistors (LEFET) with a goal of successfully demonstrating polymer injection lasers. Distributed Feedback (DFB) resonators will be imprinted directly into the light emitting polymer within the LEFET. Blends of luminescent polymers will be used to shift the emission (via Förster transfer, FRET) away from the polymer absorption to reduce losses and thereby achieve higher gain. A split-gate architecture will be introduced for separate control of electron and hole injection. Brightness will be extended to the highest level possible using pulsed LEFET operation. B. Basic physics and materials science of ?next generation? semiconducting polymers. Examples include poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) and the poly(carbazole-acceptor) alternating copolymers and related structures with D-A repeat units. Studies of the spectroscopy, photoconductivity, photo-luminescence and ultrafast photoinduced absorption will be carried out on spin-cast, blade coated, and chain-oriented films to provide fundamental information on the electronic structure of these new polymer semiconductors. Gate-induced conductivity measurements in FETs fabricated with the semiconducting polymer in the channel enable gate induced control of the carrier density and thereby enable studies of both the insulator-metal transition and the mechanism of transport in the ?metallic? state. NON-TECHNICAL SUMMARY Research in the field of semiconducting and metallic polymers has created new concepts of broad importance to interdisciplinary science; examples include detailed studies of the insulator-to-metal transition in polymers, solitons and polarons as the primary excitations in semiconducting polymers, demonstration of electroluminescent light emission from polymer light-emitting diodes, and the discovery of the novel electrochemistry of conducting polymers. Research on semiconducting polymers has resulted in the demonstration of opportunities for potentially important commercial products based upon ?printed plastic electronics?, including, for example, low cost plastic solar cells created using controlled nano-scale phase separation. The specific subjects that are the focus of this proposal, the basic science of ?next generation? semiconducting polymers and the fabrication and study of novel devices (such as the Light Emitting Field Effect Transistor) involve a combination of polymer science, condensed matter physics, device science, materials chemistry, interface chemistry and materials science. Because of its interdisciplinary nature, the research has the potential for impact across a broad range of science and technology, and it is ideally suited for the education and training of graduate students and post-doctoral researchers.