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首页> 外文期刊>ACS applied materials & interfaces >Isolating Degradation Mechanisms in Mixed Emissive Layer Organic Light-Emitting Devices
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Isolating Degradation Mechanisms in Mixed Emissive Layer Organic Light-Emitting Devices

机译：混合发光层有机发光器件中的分离劣化机制

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Degradation in organic light-emitting devices (OLEDs) is generally driven by reactions involving excitons and polarons. Accordingly, a common design strategy to improve OLED lifetime is to reduce the density of these species by engineering an emissive layer architecture to achieve a broad exciton recombination zone. Here, the effect of exciton density on device degradation is analyzed in a mixed host emissive layer (M-EML) architecture which exhibits a broad recombination zone. To gain further insight into the dominant degradation mechanism, losses in the exciton formation efficiency and photoluminescence (PL) efficiency are decoupled by tracking the emissive layer PL during device degradation. By varying the starting luminance and M-EML thickness, the rate of PL degradation is found to depend strongly on recombination zone width and hence exciton density. In contrast, losses in the exciton formation depend only weakly on the recombination zone, and thus may originate outside of the emissive layer. These results suggest that the lifetime enhancement observed in the M-EML architectures reflects a reduction in the rate of PL degradation. Moreover, the varying roles of excitons and polarons in degrading the PL and exciton formation efficiencies suggest that kinetically distinct pathways drive OLED degradation and that a single degradation mechanism cannot be assumed when attempting to model the device lifetime. This work highlights the potential to extract fundamental insight into OLED degradation by tracking the emissive layer PL during lifetime testing, while also enabling diagnostic tests on the root causes of device instability.
机译：有机发光器件（OLED）的降解通常由涉及激子和极性的反应驱动。因此，以改善OLED寿命的常见设计策略是通过工艺发光层架构来降低这些物种的密度，以实现广泛的激子重组区。这里，在具有宽重组区的混合宿主发光层（M-EML）架构中分析了激子密度对器件劣化的影响。为了进一步了解主要的降解机制，通过在设备劣化期间跟踪发光层PL，通过跟踪发光层PL去耦的激子形成效率和光致发光（PL）效率的损失。通过改变起始亮度和M-EML厚度，发现PL降解的速率依赖于重组区宽度并因此依赖于重组区宽度并因此依赖于激子密度。相反，激子形成中的损失仅取决于重组区的弱，因此可以源自发光层的外部。这些结果表明，M-EML架构中观察到的寿命增强反映了PL降解速率的降低。此外，激子和极性在降解PL和激子形成效率的变化作用表明，在试图模拟器件寿命时，不能假设动态不同的途径驱动OLED劣化，并且在试图模拟设备寿命时，不能假设单个劣化机制。这项工作强调了通过在寿命期间跟踪发光层PL来提取对OLED劣化的基本洞察的可能性，同时还可以对设备不稳定性的根本原因进行诊断测试。

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