Recent developments in improving the performance of SrS based blue thin film EL phosphors are reported. A model approach to optimizing EL material is presented, which considers activator incorporation, charge compensation, defect reduction and energy transfer processes. We demonstrate how the flexibility and accuracy of physical vapor deposition and modern characterization techniques, used in a systematic and cost effective research methodology, can improve the understanding of these issues and be used to develop more efficient thin film EL phosphors. For example, the growth of specialized materials system coupled with PL and PLE, EPR measurements were successfully used to understand the defect structure due to the valence mismatch from the doping of 3+ Ce onto the 2+ Sr site. Successful incorporation of 1+ Ag into SeS:Ce was shown not only to improve both the blue chromaticity from x equals 0.31, y equals 0.52, to x equals 0.26, y equals 0.46, and the EL brightness, but also to eliminate the thermal quenching of the emission intensity. QDLTS was used to identify the trap states and density to help the development of a low temperature annealing process for SeS:Cu. A reduction in the thermal quenching behavior due to codoping was also observed in this material.
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