Kim Sungjun, Yu Hak Ki, Hong Kihyon, Kim Kisoo, Son Jun Ho, Lee Illhwan, Kim Kyoung-Bo, Kim Tae-Yeob, Lee Jong-Lam
Department of Materials Science and Engineering, Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, South Korea.
Opt Express. 2012 Jan 16;20(2):845-53. doi: 10.1364/OE.20.000845.
We replace Indium Tin Oxide (ITO) with an MgO nano-facet Embedded WO(3)/Ag/WO(3)(WAW) multilayer for electrodes of high efficiency OLEDs. WAW shows higher values for transmittance (93%) and conductivity (1.3×10(5) S/cm) than those of ITO. Moreover, WAW shows higher transmittance (92.5%) than that of ITO (86.4%) in the blue region (<500 nm). However, due to the large difference in refractive indices (n) of glass (n=1.55) and WO(3) (n=1.95), the incident light has a small critical angle (52°). Thus, the generated light is confined by the glass/WAW interface, resulting in low light outcoupling efficiency (~20%). This can be enhanced by using a nano-facet structured MgO (n=1.73) layer and a ZrO(2) (n=1.84) layer as a graded index layer. Using these optimized electrodes, ITO-free, OLEDs with various emission wavelengths have been produced. The luminance of OLEDs using MgO/ZrO(2)/WAW layers is enhanced by 24% compared to that of devices with ITO.
我们用氧化镁纳米刻面嵌入的WO(3)/Ag/WO(3)(WAW)多层结构取代氧化铟锡(ITO)作为高效有机发光二极管(OLED)的电极。与ITO相比，WAW的透过率(93%)和电导率(1.3×10(5) S/cm)更高。此外，在蓝色区域(<500 nm)，WAW的透过率(92.5%)高于ITO(86.4%)。然而，由于玻璃(n = 1.55)和WO(3)(n = 1.95)的折射率(n)差异较大，入射光的临界角较小(52°)。因此，产生的光被玻璃/WAW界面限制，导致光出射耦合效率较低(~20%)。通过使用纳米刻面结构的氧化镁(n = 1.73)层和氧化锆(n = 1.84)层作为渐变折射率层，可以提高光出射耦合效率。使用这些优化的电极，已经制备出了无ITO、具有各种发射波长的OLED。与使用ITO的器件相比，使用MgO/ZrO(2)/WAW层的OLED的亮度提高了24%。
