Improvement in Electro-Optical Characteristics of CaS:Eu Electroluminescent Devices
Electro-optical characteristics of rare-earth doped alkaline-earth-sulfide electroluminescent(EL) devices were studied. Measurement of luminance and transferred charge responses in CaS:Eu. CaS:Ce, SrS:Eu, and SrS:Ce EL devices revealed that rare-earth luminescent centers played a decisive role in controlling electro-optical characteristics. Especially, Eu was found to be the cause of the slow electro-optical response and a sharp decrease of luminance and transferred charge with a decrease of frequency in CaS:Eu. These characteristics were improved by co-doping a small amount of Ce to CaS:Eu. Especially, by doping 0.05mol% Ce to CaS:Eu(0.2mol%), the transferred charge response time decreased one-and-a-half orders of magnitudes and became almost the same as that of ZnS:Mn.
KeywordsVoltage Dependence Luminescent Center Phosphor Layer Half Order Threshold Electric Field
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