Blue Phosphors for Thin Film Electroluminescent Displays

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Thin film electroluminescent (TFEL) display technology now produces matrix-addressed self-luminous flat panels which come very close to providing the capability for high- definition color television. The principal obstacle to advancing this technology to full color video imaging is the need for a high brightness, saturated-blue phosphor. The objective of Phase I was to show that bright blue EL phosphor can be produced from chemical vapor deposited (CVD) zinc sulfide. Ion implantation was used to introduce many different activator elements into ZnS substrates. Blue photoluminescence was found from Tm- implanted ZnS; however, a combination of other ion implanted elements gave much stronger luminescence and a deep blue color. Rutherford backscattering analysis and X-ray diffraction indicate that ion implanted CVD thin films of ZnS have favorable stoichiometry and structure for TFEL devices, which will be fabricated and tested in Phase II. Spire proposes for Phase II to continue investigation of ion implanted blue electroluminescent phosphors. TFEL structures will be fabricated from CVD-grown ZnS thin films, implanted with the new blue- emitting dopants and co-dopants, implanted with control activators such as Mn and Tm, and evaluated for EL brightness, chromaticity and persistence. Some optimization of process and device fabrication parameters will be conducted. Ion implanted TFEL devices have enormous potential for low-cost three-color displays because all phosphor colors can be formed in the same thin film substrate.