利用微球层提高有机发光二极管出光效率

Improvement of OLED Outcoupling Efficiency Using Microsphere Monolayer

采用自组装的方法(提拉法)在普通玻璃盖玻片衬底上制备了聚苯乙烯微球层,对其进行简单的热处理可获得类似微透镜的结构。利用折射率匹配液将其耦合在常规OLEDs的出光面,研究了其对器件光学特性的影响。初步的研究结果表明:热处理后的直径为3μmPS微球层可将限制在玻璃衬底中的部分光耦合到前向外部空间,并将OLEDs器件正方向的发光亮度(效率)提高大约9%。

Organic light-emitting diodes （OLEDs） are of considerable interest in flat panel displays and ligh-ting applications due to their many advantages,however,only about 20% light generated from the organic layer in the devices can escape to external forward space due to total internal reflection effect.Therefore,many methods have been used to increase the outcoupling efficiency of the devices.In this article,a monolayer of polyethylene （PS） microspheres （MS） with diameter of around 3 μm was prepared by self-assembly method on microscope cover glass.The microlens-like structure was obtained by annealing the PS MS monolayer at 120 ℃ for around 20 min.The annealed PS MS monolayer was then optically coupled （by refractive-index-matched material） on the outside of an OLED,with structure of Glass/ITO（40 nm）/NPB（40 nm）/Alq3 （60 nm）/LiF （1 nm）/Al （100 nm） as a light scattering layer.The OLEDs with the annealed monolayer of PS MS exhibit improved normal direction luminance and efficiency （about 9% at the current density of 50 mA/cm2 and the luminance round 1 250 cd/m^2） compared to the control devices,which indicated that part of the light confined within the glass substrates can be extracted to the external forward space through scattering effects of the annealed monolayer of PS MS.