The Role of Metallic Dopants in Improving the Thermal Stability of the Electron Transport Layer in Organic Light-Emitting Diodes
The Role of Metallic Dopants in Improving the Thermal Stability of the Electron Transport Layer in Organic Light-Emitting Diodes
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DOI：
10.1002/adom.201800496
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发表时间：
2018-09-04
影响因子：
9
通讯作者：
Gather, Malte C.
中科院分区：
文献类型：
--
作者：
Keum, Chang-Min;Kronenberg, Nils M.;Gather, Malte C.
4，7-二苯基-1，10-邻菲咯啉（BPhen）由于其高电子迁移率和与碱金属n型掺杂剂的良好相容性而被广泛用于有机发光二极管（OLED）中的电子传输层（ETL）。然而，由于BPhen的相对低的玻璃化转变温度（T-g），这些ETL的形态很容易通过加热而改变，并且这种变化通常降低OLED的性能。在此，报道了当用铯（Cs）掺杂其基于BPhen的ETL时OLED的热稳定性的增强。为了研究Cs掺杂剂在BPhen基体中的作用，研究了不同掺杂浓度的Cs掺杂BPhen薄膜的结晶特性。接下来，在高达100摄氏度的温度下退火OLED之后，表征含有Cs掺杂的BPhen ETL的蓝色荧光和红色磷光OLED的电学和光学性质。Cs在抑制BPhen膜的不期望的结晶中起关键作用，这增强了OLED的热稳定性超过纯BPhen的T-g。最后，展示了在80摄氏度下通过原子层沉积封装的高度稳定的BPhen基OLED。这项工作可能会导致一个新的策略，提高固有的热耐久性的有机器件和它们的兼容性与热要求高的过程。
4,7-Diphenyl-1,10-phenanthroline (BPhen) is widely used to create the electron transport layer (ETL) in organic light-emitting diodes (OLEDs) because of its high electron mobility and good compatibility with alkali metal n-dopants. However, the morphology of these ETLs is easily altered by heating due to the relatively low glass transition temperature (T-g) of BPhen and this change often reduces the performance of OLEDs. Here, an enhancement in the thermal stability of OLEDs when doping their BPhen-based ETLs with cesium (Cs) is reported. To investigate the role of the Cs dopant in the BPhen matrix, the crystallization features of Cs-doped BPhen films with different doping concentrations are examined. Next, the electrical and optical properties of blue fluorescent and red phosphorescent OLEDs containing Cs-doped BPhen ETLs are characterized after annealing the OLEDs at temperatures up to 100 degrees C. Cs plays a critical role in inhibiting the undesired crystallization of BPhen films, which enhances the thermal stability of OLEDs beyond the T-g of neat BPhen. Finally, highly stable BPhen-based OLEDs encapsulated via atomic layer deposition at 80 degrees C are demonstrated. This work may lead to a new strategy for enhancing the intrinsic thermal durability of organic devices and their compatibility with thermally demanding processes.