AC Electroluminescence: Optimisation of Phosphors

This project is aimed at extending the performance of AC electroluminescent (ACEL) phosphor powders for a wide range of display applications.Currently the best ACEL phosphor powders can be made into devices that have working lives around 2000-3000 hours at reasonable brightness in subdued lighting. Along with our partner companies (Pelikon and Kodak UK Ltd.) we will investigate the reasons for their degradation (both coated ar uncoated phosphors) so that a full understanding of the factors limiting their lifetimes and brightness can be understood. This study is timely because: some of the techniques necessary to do this work have only become available to the non-specialist in the last 5 years or so. For instance, using Rarr microscopy, it will be possible to examine the interfaces between the transparent coatings and the phosphor surfaces in individual particles under a variety of working conditions in a range of different chemical environments.Using new solution methods for precipitating phosphor precursor powders (homogeneous precipitation methodology) developed in the Centre for Phosphors and Display Materials at the University of Greenwich (again in the last 5 years, hence timely), so we will synthesise new ACEL phosphor powders that have improved brightness levels and longer lifetimes. This will be achieved by incorporating into the phosphor design changes both in concentration and distribution of active light-emitting centres from knowledge gained through understanding the current state-of-the-art. Fine control the number and distribution of these centres is possible from our new methods of precipitation from solution. We will also develop methods of coating the powders to further extend their lifetimes making use of our understanding of the role of the coating in commercial phosphors. Polymeric supports will be used to control particle size and morphology. The new synthetic technology developed at Greenwich will be scaled up for industrial production the laboratories of Kodak UK Ltd. We will work with Kodak UK Ltd. to transfer the technology developed at the University of Greenwich to their plant industrial production.