Krotkus Simonas, Kasemann Daniel, Lenk Simone, Leo Karl, Reineke Sebastian
Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany.
Light Sci Appl. 2016 Jul 15;5(7):e16121. doi: 10.1038/lsa.2016.121. eCollection 2016 Jul.
White organic light-emitting diodes (OLEDs) are promising candidates for future solid-state lighting applications and backplane illumination in large-area displays. One very specific feature of OLEDs, which is currently gaining momentum, is that they can enable tunable white light emission. This feature is conventionally realized either through the vertical stacking of independent OLEDs emitting different colors or in lateral arrangement of OLEDs. The vertical design is optically difficult to optimize and often results in efficiency compromises between the units. In contrast, the lateral concept introduces severe area losses to dark regions between the subunits, which requires a significantly larger overall device area to achieve equal brightness. Here we demonstrate a color-tunable, two-color OLED device realized by side-by-side alignment of yellow and blue p-i-n OLEDs structured down to 20 μm by a simple and up-scalable orthogonal photolithography technique. This layout eliminates the problems of conventional lateral approaches by utilizing all area for light emission. The corresponding emission of the photo-patterned two-unit OLED can be tuned over a wide range from yellow to white to blue colors. The independent control of the different units allows the desired overall spectrum to be set at any given brightness level. Operated as a white light source, the microstructured OLED reaches a luminous efficacy of 13 lm W at 1000 cd m without an additional light outcoupling enhancement and reaches a color rendering index of 68 when operated near the color point E. Finally, we demonstrate an improved device lifetime by means of size variation of the subunits.
白色有机发光二极管（OLED）是未来固态照明应用和大面积显示器背板照明的有前途的候选者。OLED的一个非常特殊的特性，目前正越来越受到关注，就是它们能够实现可调谐的白光发射。这个特性通常通过发射不同颜色的独立OLED的垂直堆叠或OLED的横向排列来实现。垂直设计在光学上难以优化，并且常常导致各单元之间的效率折衷。相比之下，横向概念会给亚单元之间的暗区带来严重的面积损失，这需要显著更大的整体器件面积才能实现同等亮度。在此，我们展示了一种通过简单且可扩展的正交光刻技术将黄色和蓝色p-i-n OLED并排排列，结构尺寸小至20μm实现的颜色可调谐双色OLED器件。这种布局通过利用所有面积进行发光消除了传统横向方法的问题。光图案化的双单元OLED的相应发射可以在从黄色到白色再到蓝色的很宽范围内进行调谐。对不同单元的独立控制允许在任何给定亮度水平下设置所需的整体光谱。作为白光源运行时，这种微结构OLED在1000 cd m时无需额外的光出射增强即可达到13 lm W的发光效率，在接近色点E运行时显色指数达到68。最后，我们通过亚单元尺寸变化展示了器件寿命的改善。
