NSF-Europe: Materials for Electrochemical Luminescent Devices

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This is a collaborative project between researchers at the University of Texas, Austin and at Dipartimento Di Chimica G. Ciamician, Universita Degli Studi Di Bologna, Italy. This project and its Italian counterpart are focused on the synthesis and (spectro-) electrochemical characterization of new classes of compounds that display electrochemically induced luminescence. The primary compounds that are the object of study are Ru(bipyridine)(terpyridine) complex derivatives. An added value of the collaboration with the research group in Italy is the possibility of extending the study to other Ru-complex derivatives, e.g., using substituted bipyridines and phenanthrolines, which could provide materials with increased quantum efficiencies and improved operating lifetimes. It could also be useful to utilize various counterions ranging from OH- that has higher mobility, compared to ClO4 - and BF4 -, to very big ions whose size will effectively hinder ion transport (e.g., p-dodecylbenzenesulphonate). The use of latter ions could assist in elucidating the role of ion mobility and the possibility of other charge injection mechanisms for the light-emitting devices. Molecular characterization in solution will be done by two different electrochemical luminescence detector instruments (one mounting a PMT camera, the other a CCD camera) and a dry box to prepare the solutions under controlled conditions. After an evaluation of the characteristic properties of the system (quantum efficiency, durability) these will be compared to a 'standard' light emitting system to judge the relative quality and the quantitative efficiency of these new molecules. The preparation of solid-state light emitting devices (OLEDs) based on these molecular systems is a prime target of the project. Therefore, effort will be placed on the search for suitable conditions under which these substances can be attached to a surface, mainly indium tin oxide (ITO), to form useful thin layers. Techniques such as spin coating, vapor deposition, and electrochemical deposition will be used. A study on the effect of material purity and structure on the properties of the products will be also carried out. Additionally, scanning probe microscopy will be employed to investigate these films. Preliminary experiments with a tuning fork-based scanning tunneling microscope have demonstrated the ability to produce simultaneous light emission, current, and topographic images of molecular thin films. This new and information-rich technique can be readily employed in the study of these new materials.%%% The project addresses fundamental research issues associated with electronic/photonic materials having technological relevance. An important feature of the project is the strong emphasis on education, with emphasis on integration of research and education, and an international collaboration providing both scientific and educational benefits. An important component of this interaction will be exchange of students for extended periods of time. This NSF project is co-funded by the Division of Materials Research, and the International Office (Western Europe) as a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135). This project is being carried out in collaboration with the Universita Degli Studi Di Bologna, Italy.