Improving the Thermal Stability of Top-Emitting Organic Light-Emitting Diodes by Modification of the Anode Interface,Advanced Optical Materials

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Improving the Thermal Stability of Top-Emitting Organic Light-Emitting Diodes by Modification of the Anode Interface
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2020-11-20 , DOI: 10.1002/adom.202001642
Yali Deng ₁ , Changmin Keum ₁ , Sabina Hillebrandt ₁ , Caroline Murawski _{1,

2} , Malte C. Gather _{1,

3}

Affiliation

Top-emitting organic light-emitting diodes (OLEDs) are of interest for numerous applications, in particular for displays with high fill factors. To maximize efficiency and luminance, molecular p-doping of the hole transport layer (p-HTL) and a highly reflective anode contact, for example, made from silver, are used. Atomic layer deposition (ALD) is attractive for thin film encapsulation of OLEDs but generally requires a minimum process temperature of 80 °C. Here it is reported that the interface between the p-HTL and the silver anode of top-emitting OLEDs degrades during an 80 °C ALD encapsulation process, causing an over fourfold reduction in OLED current and luminance. To understand the underlying mechanism of device degradation, single charge carrier devices are investigated before and after annealing. A spectroscopic study of p-HTLs indicates that degradation is due to the interaction between diffusing silver ions and the p-type molecular dopant. To improve the stability of the interface, either an ultrathin MoO₃ buffer layer or a bilayer HTL is inserted at the anode/organic interface. Both approaches effectively suppress degradation. This work shows a route to successful encapsulation of top-emitting OLEDs using ALD without sacrificing device performance.

中文翻译：

通过修改阳极界面提高顶发射有机发光二极管的热稳定性

顶部发光的有机发光二极管 (OLED) 在众多应用中受到关注，特别是对于具有高填充因子的显示器。为了最大限度地提高效率和亮度，使用了空穴传输层 (p-HTL) 的分子 p 掺杂和高反射阳极触点，例如，由银制成。原子层沉积 (ALD) 对 OLED 的薄膜封装很有吸引力，但通常需要 80 °C 的最低工艺温度。据报道，在 80°C ALD 封装过程中，p-HTL 和顶部发光 OLED 的银阳极之间的界面会退化，导致 OLED 电流和亮度降低四倍以上。为了了解器件退化的潜在机制，在退火前后对单电荷载流子器件进行了研究。p-HTL 的光谱研究表明降解是由于扩散的银离子和 p 型分子掺杂剂之间的相互作用。为了提高界面的稳定性，超薄 MoO₃缓冲层或双层 HTL 插入阳极/有机界面。这两种方法都有效地抑制了退化。这项工作展示了在不牺牲器件性能的情况下使用 ALD 成功封装顶部发光 OLED 的途径。

更新日期：2020-11-20

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