GOALI/FRG: Full-Color Phosphors for Electroluminescent Displays

Oregon State University, Corvallis OR

Investigators

Abstract

This GOALI project is a collaborative effort between researchers at Oregon State University and Planar Systems, Inc., Beaverton, OR. Primary goals are to increase basic understanding of luminescent materials, and to exploit their properties to achieve bright, efficient, and manufacturable red, green, and blue (RGB) phosphors for use in flat-panel displays. The approach involves three basic routes: (i) Luminescent impurity and defect engineering of conventional sulfide phosphors, ZnS, SrS, and CaS., (ii) Exploratory development of novel, low-temperature sulfide, selenide, and telluride phosphors-BaS and MX (M=Mg, Ca, Sr; X=Se, Te.), (iii) Optimization of oxide phosphors. A variety of conventional and unconventional luminescent impurities will be investigated. Defect engineering will involve compensation, color-shifting, and/or vacancy scavenging considerations. The viability of oxides, e.g., Zn2GeO4:Mn and Zn2SixGe1-xO4:Mn, as phosphors will be assessed by identifying the physical mechanisms that limit device performance and then developing performance-improvement strategies. Phosphor studies will be conducted using a rapid-throughput process. New phosphor, luminescent impurity, co-activator materials systems will be synthesized as powders, and their performance assessed and optimized through photoluminescence characterization. In this manner, luminescent impurity incorporation, defect engineering, and alloying studies will be integrated with thin film processing and characterization which will be carried out with promising powder phosphors. Thin-film evaporation source material and sputter targets will be synthesized using solid-state synthesis/processing methods. Two techniques will be investigated to incorporate luminescent impurities and co-activators into phosphor thin films, conventional in situ doping during thin-film deposition and 'flux doping.' Finally, alternating current thin film EL (ACTFEL) devices will be fabricated and tested to appraise the viability of a given phosphor system for applications. This research procedure involving powder synthesis, processing and characterization, followed by luminescence assessment, thin film 'flux doping', and ACTFEL performance represents a general methodology-additional basic materials studies to identify and gain understanding of fundamental mechanisms will be carried out as well. %%% The project addresses basic research issues in a topical area of materials science with high technological relevance. The basic knowledge and understanding gained from the research is expected to contribute to improving US competitiveness in the international display technology market. The availability of low-temperature phosphors would result in superior products at reduced cost and improved manufacturability. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The multidisciplinary (chemistry, electrical engineering, physics) and industrially-connected nature of this GOALI program offers unique educational opportunities for students to experience a teamwork-oriented research environment from both academic and industrial perspectives. The project is co-supported by the DMR/EM, DMR/CER, and DMR/SSC programs, and the MPS OMA(Office of Multidisciplinary Activities). ***