Fundamentals in Organic Light Emitting Diodes

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Solid-state electronic devices such as transistors and lasers have been continuously transforming the society we live in today. Solid-state light-emitting devices, however, has not conquered Edison's incandescent light bulbs. The light bulbs are quite wasteful; some 98% of the energy input ends up as heat instead of light. US department of Energy has estimated that energy efficient solid-state lightings, if broadly adopted, would provide approximately 190 terawatt-hours in energy saving, which would reduce green house emissions by 31.4 million metric tons of carbon. This proposal is to focus on studying surface and interface materials which are key to develop simple and efficient organic light emitting diodes (OLED) and thus would help accelerate the transition from bulb to solid-state lightings. Specifically, this proposed NSERC discovery research program will include the following research objectives: (a) Anode interface; we will investigate the scientific principles and fabrication methods of high work function anodes using surface monolayer termination method such as chlorination. The goal is to improve OLED lifetime through stabilized electrode-organic interface and to improve charge balance factor. (b) Cathode interface and electron injection buffer layer; we will develop a versatile nano-composite buffer materials which will simultaneously optimize several key parameters including optical constant matching at the interface, thermal conduction, and electrical conductivity. The goal is to improve charge balance factor and optical coupling. (c) Organic heterojunctions; we will investigate the various processes leading to the formation of excitons. The exciton's subsequent diffusion, radiative recombination, non-radiative recombination , interaction with accumulated charges will be investigated. The goal is to uncover guiding scientific principles in designing organic heterojunctions for maximum photon generation rate .