Durable Molecular Organic Electroluminescent Devices and Their Frequency Responses to a New Accurate Driving Method(Special Issue on Organic Materials for Optics and Electronics)

概要

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In order to improve the running durability of organic electroluminescent devices(OELDs), the doping sites of molecular OELDs were optimized, and the frequency responses of the optimized devices were examined for Mg-In/bis(10-hydroxybenzo[h]quinolinato)beryllium(BeBq_2)/N, N'-diphenyl-N, N'-(3-methylphenyl)-1, 1'-biphenyl-4, 4'-diamine(TPD)/4, 4', 4"-tris(3-methylphenylphenylamino)triphenylamine(MTDATA)/ITO. The TPD hole transport layer was the optimum doping site for 5, 6, 11, 12-tetraphenylnaphthacene(rubrene)dopant, and a very high efficiency of 13cd/A at 0.13kcd/m^2 was obtained for yellow emission. Half-decay times under a constant direct current density of 1.0mA/cm^2 from an initial luminance of 0.13kcd/m^2 extended to longer than 26,000 hours. The luminance of the optimized device decreases lineally with respect to the logarithm of the frequency as the frequency increases in the range from 1kHz to 0.3MHz when a square wave with a duty ratio of 50% and a maximum voltage of 5.0V is applied. A new driving method involving frequency modulation is proposed. This may offer accurate control of pixel luminance, and enable simple driving circuits adapted to highly integrated digital LSI chips, or the concept of system on glass.
社団法人電子情報通信学会の論文
1998-07-25