| Summary: | 碩士 === 國立高雄應用科技大學 === 電子與資訊工程研究所碩士班 === 95 === In this thesis, we proposed an equivalent circuit model and measured various parameters of the alternating-current thick-film electro- luminescent device. Combined with the luminance-charge relation of the phosphor layer deduced by experiment and Sawyer-Tower circuit measurement, we can calculate and predict the voltage-luminance characteristics of the electroluminescent device with various dielectrics composition. Compared with the theoretical calculation and experimental result, the deviation is less than 20% and proves the validity of our proposed equivalent circuit model. Both theory and experimental results indicated that the luminance of the electroluminescent device is linear dependent with phosphor layer charges. However, phosphor layer charges do not proportional to the capacitance value of the dielectric layer. Charges will get saturation and induces the saturation of luminance of the device. For example, when we increases the capacitance of the dielectric layer to 10nF with a 2 cm × 2 cm sample, the phosphor layer charges will reach 90% of the saturation value. The luminance of the electro- luminescent device will be limited no matter what other dielectric materials and compositions are adopted.
In order to improve the luminance efficiency and drift the color, we doped D-YAG powder into the phosphor layer. The D-YAG powder would absorb blue and blue-green light and emit green light. It makes the emitting light of the electroluminescent device moving to the sensitive area of human eyes and enhanced the luminance. When operated at 150V and 400Hz of alternating-current voltage, the CIE coordinate shifted from (0.16, 0.36) to (0.20, 0.43) and the luminance efficiency increased 10% for the electroluminescent device composed by GG24 phosphor and D-YAG powder. By mixing the GG64 phosphor and D-YAG powder, the CIE coordinate of the electroluminescent device changed from (0.158, 0.197) to (0.21, 0.29) and the luminance efficiency increased 20%.
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