介观光学结构提高蓝色顶发射有机电致发光器件效率

利用宽带有机半导体材料(2, 9-二甲基-4, 7-二苯基-1, 10-菲啰啉, BCP)形成无序介观光学结构来提高蓝色顶发射有机电致发光器件(OLED)的出光效率,从而提升器件的外量子效率.基于BCP折射率匹配的作用,在顶电极上增加一层BCP薄膜,器件内的波导光能够被进一步散射出来,且由于此材料本身具有低的玻璃化转变温度,在一定的环境条件下(温度及湿度)下BCP易发生自聚集结晶而形成无序介观光学结构,藉此结构使原来被限制于表面等离激元(SPP)的能量而耦合成自由光场,从而被有效提取出来.通过BCP结构薄膜的作用,器件最大亮度从4500 cd·m^-2提升至9840 cd·m^-2,外量子效率(EQE)从0.42%提升至1.14% (提高了1.7倍),此外光谱也蓝移12 nm,实现了蓝色发光光谱的优化.

Mesoscopic Optical Structure to Enhance the Out-Coupling Efficiency of Blue Top OLED

In this study, mesoscopic optical structured 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenyl-1, 10-phenanthrolin (bathocuproine, BCP) film was formed to enhance the out-coupling efficiency of a top blue organic light-emitting device (OLED). Based on the refractive index matching layer of BCP on the electrode, the light can be extracted through waveguide mode. Owing to the low glass transition temperature (T_g) of BCP, which easily self-aggregates in a specific environment (controlled temperature and humidity), a mesoscopic optical structure was obtained in 3 h after film formation. Through the nano-aggregated structure, the surface plasmon polariton (SPP) mode can match the free optic field. The efficiency of the device was enhanced: the max brightness increased from 4500 to 9840 cd·m^-2 and the external quantum efficiency (EQE) increased from 0.42% to 1.14%. This leads to a 2.7-fold enhancement of top emission devices. Moreover, the EL spectra of the devices are also optimized by a blue-shift of 12 nm.