Lee Jooyoung, Kwon Yun Young, Choi Eun-Ho, Park JeongWoo, Yoon Hong, Kim Hyunbin
Opt Express. 2014 May 5;22 Suppl 3:A705-14. doi: 10.1364/OE.22.00A705.
We investigate two types of internal light-extraction layer structures for organic light-emitting diodes (OLEDs) that consist of silica nanoparticles (NPs) embedded in high-refractive-index TiO₂ matrices. The composite of silica NPs and TiO₂ matrices was coated on the glass substrate and fabricated with and without a SiO₂ planarization layer. An increase in the optical out-coupling efficiency by a factor of 2.0 was obtained at a high luminance of 3,000 cd/m² from OLEDs containing the silica NPs embedded in TiO₂ matrices between glass substrates and Zn-doped In₂O₃ (IZO) electrodes after additional planarization processes. This is consistent with the analytical result using the finite-difference time-domain (FDTD) method. Randomly distributed silica NPs acting as scattering centers could reduce the optical loss when extracting light. By using additional planarization processes with a PECVD-derived SiO₂ layer, one can assure that smoother surfaces provide higher out-coupling efficiency, which attain 100% and 97% enhancements in power (lm/W) and current (cd/A) efficiencies, respectively.
我们研究了用于有机发光二极管（OLED）的两种类型的内部光提取层结构，其由嵌入高折射率TiO₂基质中的二氧化硅纳米颗粒（NP）组成。二氧化硅NP与TiO₂基质的复合材料被涂覆在玻璃基板上，并在有和没有SiO₂平坦化层的情况下进行制备。在经过额外的平坦化工艺后，从包含嵌入在玻璃基板和掺锌氧化铟（IZO）电极之间的TiO₂基质中的二氧化硅NP的OLED中，在3000 cd/m²的高亮度下获得了2.0倍的光外耦合效率提高。这与使用时域有限差分（FDTD）方法的分析结果一致。作为散射中心的随机分布的二氧化硅NP在提取光时可以减少光损失。通过使用由PECVD衍生的SiO₂层进行额外的平坦化工艺，可以确保更光滑的表面提供更高的外耦合效率，其分别在功率（lm/W）和电流（cd/A）效率方面实现了100%和97%的提高。
