通过释放超长寿命的俘获电荷，低温操作掺杂 OLED 的发光强度提高十倍,Advanced Functional Materials

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通过释放超长寿命的俘获电荷，低温操作掺杂 OLED 的发光强度提高十倍
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2023-07-12 , DOI: 10.1002/adfm.202305560
Jing Chen ₁ , Xi Zhao ₁ , Huiyao Wang ₁ , Yunxi Jiang ₁ , Xiantong Tang ₂ , Yuting Wu ₁ , Fuxian Wei ₁ , Zuhong Xiong ₁

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尽管将有机荧光团掺杂到主体基质中是获得高效有机发光二极管（OLED）的常见方法，但在掺杂剂分子上经常观察到捕获电荷，这被认为不利于其光电性能的进一步增强。令人惊讶的是，在 20 K 工作温度的掺杂 OLED 中检测到了具有 >2 h 超长寿命的俘获电荷，这在之前的文献中从未发现过。然而，观察结果表明，这些俘获电荷的较长寿命主要取决于俘获电子和空穴之间较大的间距，而不是仅仅由公认的俘获态能级深度决定。更令人惊奇的是，与仅由传统恒压源驱动的器件相比，由交替的正负脉冲电压供电的低温操作掺杂OLED的发光强度提高了十倍，因为施加的负脉冲电压可以帮助这些器件超长寿命的俘获电子和空穴可以解俘获，然后彼此重新结合以产生增强的光发射。因此，这项研究阐明了捕获电荷的动态行为，为获得在外太空或航空航天领域等低温环境下工作的高性能OLED铺平了道路。

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Tenfold Enhancement in Light Emission from Low-Temperature Operational Doped OLEDs by Detrapping Super-Long-Lived Trapped Charges

Although doping organic fluorophores into host matrix is a common way to obtain high-efficiency organic light-emitting diodes (OLEDs), trapped charges are often observed on dopant molecules that are considered to be detrimental to the further enhancement of their photoelectric performances. Surprisingly, trapped charges with a super-long lifetime of >2 h are detected in doped OLEDs operated at 20 K, which has never been discovered previously in the literature. However, the observations demonstrate that the longer lifetimes of these trapped charges are primarily governed by the larger spacing distances between trapped electrons and holes, rather than being solely determined by the well-accepted energy-level depth of trap states. More amazingly, compared with the device driven only by a conventional constant voltage source, a tenfold enhancement in light emission is achieved in low-temperature operational doped OLEDs powered by an alternating positive and negative pulse voltage, because the applied negative pulse voltage can assist these super-long-lived trapped electrons and holes to detrap and then recombine with each other for producing enhanced light-emission. Therefore, this study clarifies the dynamic behaviors of trapped charges and paves the pathway for obtaining high-performance OLEDs working in low-temperature circumstances such as outer-space or aerospace fields.

更新日期：2023-07-12

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