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掺杂式OLED的结构、EL特性及其工作机制研究

Study in Structure, EL and Mechanism of Doped OLED

【作者】 李明涛

【导师】 李文连;

【作者基本信息】 中国科学院研究生院(长春光学精密机械与物理研究所) , 凝聚态物理, 2005, 博士

【摘要】 有机电致发光器件(OLED)的一个重要用途是在平板显示领域。另一方面,有机白光电致发光器件(WOLED)也越来越受到人们的关注。WOLED可以用于液晶显示的背照明光源,全色显示,还有可能用于普通照明。采用掺杂的方法可以显著提高OLED的效率和稳定性并获得理想的发光颜色。通常含8-羟基喹啉铝(AlQ)的OLED中产生的AlQ空穴阳离子造成了器件效率的降低。本论文以空穴传输材料NPB为基质,分别以DCJTB、C-545T、TBP和Rubrene为掺杂剂,并选用TPBI作空穴阻挡和电子传输层。通过改变NPB基质的厚度大大提高了效率。这归结于器件中形成的窄的限制复合区对载流子复合效率和激子能量传递效率的提高。同样以NPB和Rubrene分别为基质和掺杂剂,利用它们的蓝光和黄光获得了发光颜色稳定的白光器件。虽然电压升高引起的复合区移动使蓝光发射增强,但是Rubrene的陷获作用亦使黄光发射增强。这两种变化的共同作用使得白光颜色在一定电压范围内几乎不依赖于电场。该方法解决了白光器件中普遍存在的颜色随电场变化的现象。将C-545T、Rubrene和DCJTB分别掺杂在NPB中形成绿、黄、红三个发光层,并利用空穴传输层NPB的蓝光,获得了具有照明特性的白光。再用(btmp)2Ir(acac)替代DCJTB进一步提高器件的效率。(bpiq)2Ir(acac)的EL效率随电流密度的变化曲线证实了这类苯基异喹啉

【Abstract】 Organic light-emitting device (OLED) is a promising candidate for next generation flat plane display (FPD). On the other hand, white organic light-emitting device (WOLED) has been attracting considerable attention recently due to their potential applications as backlights for liquid crystal displays, full-color displays, and even general lighting.The efficiency, stability and emission color can be improved by doping dye into suitable host. Usually, the AlQ cation is unstable and served as a quenching center in AlQ-based device. Thus, the efficiency and stability are decreased. In this thesis, DCJTB, C-545T, TBP and Rubrene are doped into NPB host respectively. TPBI acts as an electron-transporting and hole-blocking layer. The results show that the EL efficiencies of these devices can be improved by decreasing the thickness of NPB host, which attributed to the enhanced recombination and improved energy transfer efficiency in narrow confined recombination zone.An efficient WOLED is obtained by doping Rubrene into a thin layer of NPB host. The emission color is undependent on the bias, which is due to two factors, one is the blue emission will be enhanced with the increasing bias, the other is the yellow emission will also be enhanced

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