新型λ/2微腔结构有机电致发光器件的设计与制备及相关器件物理问题研究

In this proposal，we will design and optimize the structure of an microcavity organic laser which formed by an high efficiency OLED with a high Q microcavity. We will prepare new electrodes with high conductivity and low absorption according to light-induced absorption; modulation its electromagnetic distribution; adjust thicknesses of organic functional layers; deduce the losses caused by non-radiation process; improve the probability of microcavity organic electrically pumping laser. The design rules can be summarized as follow: in the emission layer, guest-host systems, with low self-absorption, should be used. Thus, the waveguide attenuation for the laser mode can be reduced. The injection　of electrons and holes has to be balanced in order to achieve homogeneous exciton　generation in the emission layer. By combine the electrode and the mirror, low optical absorption and highly reflective electrical contacts at organic-electrode interface was obtained. We discusses various loss processes which especially occur at high excitation and whose impact is in particular striking for organic laser diodes. Potential devices for an organic injection laser have to combine a low attenuation laser waveguide with the ability to support high current densities.

本项目拟以光学设计为手段，从微腔有机电致发光器件（OLED）各功能层优化入手，将新型高电流密度下高效率OLED与高Q值微腔结合，利用光诱导吸收原理设计并制备新型高导电性、低光学吸收的透明导电电极（TCO），模拟腔内电磁场及光场分布，调节器件各功能层厚度及界面，将发光层设计在驻波场波腹，有机功能层与阴、阳极界面设计在驻波场波节以降低各种非辐射损耗，以期获得高性能λ/2 微腔结构的有机微腔器件。简单地说: 1)底部分布式布拉格反射镜（DBR）采用高、低折射率的λ/4 厚薄膜交替生长而成，最后一层高折射率层采用新型TCO，降低器件阳极损耗；2)采用薄层金属膜与DBR结合获得中心波长处低光学损耗的阴极结构；3)研究OLED发光层插入超薄绝缘层薄膜使器件效率非线性增加的物理机制，结合微腔结构器件的各种激子猝灭过程的跃迁速率，提高器件性能，从理论上推算以该结构制备有机电泵浦激光器的精确阈值电流密度。

提高有机电致发光器件（OLED）在高电流密度下的发光效率是OLED研究中迫切需要解决的重要科研问题之一，本文中，我们在以C545T掺杂Alq3为发光层的有机小分子绿光发光器件中的发光层与电子传输层之间插入超薄LiF绝缘层，器件的外量子效率随着电流密度的增加始终没有降低，直至达600mA/cm2时达到最大值 4.79%，是相同电流密度下的参考器件的外量子效率的7倍。实验结果表明该方法可简单有效降低OLED在高电流密度下损耗，避免器件效率降低，从而提高器件的性能。.采用双源电子束设备制备了一种IPTO透明导电薄膜，通过开尔文探针法测试，其功函数为5.14eV。新型IPTO薄膜的可见光透过率及导电性与商业化的ITO薄膜可媲美。因此，我们将IPTO替代商业化ITO作为阳极制备了有机电致发光器件，基于IPTO阳极器件的最大亮度为85140 cd/m2，最大外量子效率为3.16%，分别为基于ITO阳极器件的最大亮度及最大外量子效率的3倍及1.13倍。实验结果表明以IPTO为阳极制备有机电致发光器件可以提高器件性能。