Optimizing OLED Structures for a‐Si Display Applications via Combinatorial Methods and Enhanced Outcoupling
Optimizing OLED Structures for a‐Si Display Applications via Combinatorial Methods and Enhanced Outcoupling
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通过组合方法和增强的输出耦合优化非晶硅显示应用的 OLED 结构
DOI：
10.1002/pssa.200404347
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
H. Riel
中科院分区：
文献类型：
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作者：
W. Riess;T. Beierlein;H. Riel
由非晶硅（a-Si）薄膜晶体管（TFT）驱动的有源矩阵有机发光显示器需要上级有机发光器件（OLED）性能，以实现足够的像素亮度并避免a-Si晶体管的劣化。此外，高分辨率全色显示器的a-Si TFT电路可能变得相当复杂，因此占据大量的像素面积，导致常规底部发射OLED的孔径比显著降低。因此，顶部发射器件架构是有利的。在本文中，我们描述了通过组合方法优化顶部发光OLED和增强外耦合的一般概念。为了优化OLED性能，我们使用组合器件制造。我们的系统允许在一个衬底上同时制造10 × 10个单独的器件，从而能够系统地改变材料组合和电极以及器件参数，例如层厚度，层序列和染料掺杂剂浓度。在第一部分中，我们提出了一个概述的能力，组合方法的电气和电光器件优化。我们展示了从三层器件到磷光五层OLED的多层OLED的结果。第二部分描述了一个外耦合的概念，允许顶部发光OLED的发射特性进行定制。我们证明了这一点，并分析了如何角强度分布和光谱特性可以调整。通过简单地改变沉积在半透明金属电极上的电介质层的光学厚度，可以增强光的外耦合。使用这种覆盖层的概念，在前向方向上的出耦合光强度增加了1.7倍，同时伴随着实现高的色纯度。覆盖层概念的优势特别在于可以分别优化光学和电学器件性能。使用优化的层厚度和覆盖概念，我们实现了从分离的红色，绿色和蓝色子像素超过22 cd/A在现实的显示驱动条件下，从而使世界上最大的（20英寸）的a-Si有源矩阵OLED显示器的效率的OLED（国家电视标准委员会）白色。（© 2004 WILEY-VCH Verlag GmbH & Co. KGaA，魏因海姆）
Active-matrix organic light-emitting displays driven by amorphous silicon (a-Si) thin-film transistors (TFT) require superior organic light-emitting device (OLED) performance in order to achieve sufficient pixel brightness and to avoid degradation of the a-Si transistors. In addition, the a-Si TFT circuitry of high-resolution full-color displays can become rather complex and therefore occupies a large amount of the pixel area, leading to a significantly reduced aperture ratio with conventional bottom-emitting OLEDs. A top-emitting device architecture is therefore advantageous. In this paper we describe general concepts for optimizing top-emitting OLEDs via combinatorial methods and for enhancing outcoupling. To optimize OLED performance, we use combinatorial device fabrication. Our system allows the simultaneous fabrication of 10 × 10 individual devices on one substrate, enabling a systematic variation of material combinations and electrodes as well as of device parameters such as layer thickness, layer sequence, and dye dopant concentrations. In the first part, we present an overview of the capabilities of combinatorial methods for electrical and electro-optical device optimization. We show results on multilayer OLEDs ranging from trilayer devices to phosphorescent five-layer OLEDs. The second part describes an outcoupling concept that allows the emission characteristics of top-emitting OLEDs to be tailored. We demonstrated that and analyzed how the angular intensity distribution and the spectral characteristics can be tuned. Light outcoupling can be enhanced by simply varying the optical thickness of a dielectric layer deposited on top of a semitransparent metal electrode. Using this capping-layer concept the outcoupled light intensity in forward direction was increased by a factor of 1.7 while concomittantly achieving a high color purity. The strength of the capping-layer concept is in particular that the optical and the electrical device performance can be optimized separately. Using optimized layer thicknesses and the capping concept, we achieve an efficiency of NTSC (National Television Standard Committee) white from separate red, green and blue sub-pixels exceeding 22 cd/A under realistic display-driving conditions, thus enabling the world's largest (20-inch) a-Si active-matrix OLED display. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)