In organic light-emitting diodes (OLEDs), understanding the efficiency loss mechanism known as exciton-polaron quenching (EPQ) has been a longstanding challenge. Traditionally, EPQ was believed to occur mainly within the bulk of the OLED emission layer (EML) due to the coexistence of polarons and excitons, limiting our understanding of its full impact. Here, we report a previously overlooked phenomenon termed “interfacial EPQ (Inf. EPQ),” which occurs at the heterointerface between the EML and the adjacent charge transport layer (CTL). We observe the direct transfer of EML excitons to CTL polarons across this interface, spanning distances of up to 4 nm. Notably, Inf. EPQ exceeds EPQ within the EML bulk, even in devices with a slight interfacial energy barrier (>0.2  eV). We propose a methodology that enables independent probing of Inf. EPQ, systematic validation of its essential parameters, and the identification of Dexter energy transfer as its governing mechanism. Importantly, our findings highlight Inf. EPQ as a ubiquitous phenomenon across devices with various luminescent mechanisms, wavelengths, and injection levels. By effectively addressing Inf. EPQ, we achieve efficiency enhancements in red, green, and blue phosphorescent OLEDs, by 70%±8%, 47%±5%, and 66%±6%, respectively. Our work advances the physical understanding of exciton and polaron dynamics at organic heterointerfaces, providing universally applicable solutions to Inf. EPQ-related issues in practical devices.

中文翻译：

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有机发光二极管中的界面激子-极化子猝灭


在有机发光二极管 （OLED） 中，了解称为激子-极化子猝灭 （EPQ） 的效率损失机制一直是一项长期挑战。传统上，由于极化子和激子共存，EPQ 被认为主要发生在 OLED 发射层 （EML） 的大部分内，这限制了我们对其全部影响的理解。在这里，我们报告了一种以前被忽视的现象，称为“界面 EPQ （Inf. EPQ）”，它发生在 EML 和相邻电荷传输层 （CTL） 之间的异质界面处。我们观察到 EML 激子通过该界面直接转移到 CTL 极化子，跨越的距离高达 4 nm。值得注意的是，在 EML 本体中，Inf. EPQ 超过了 EPQ，即使在具有轻微界面能垒 （>0.2 eV） 的器械中也是如此。我们提出了一种方法，可以独立探测 Inf. EPQ，系统验证其基本参数，并确定 Dexter 能量转移作为其控制机制。重要的是，我们的研究结果强调 Inf. EPQ 在具有不同发光机制、波长和注射水平的器件中普遍存在。通过有效解决 Inf. EPQ，我们实现了红色、绿色和蓝色磷光 OLED 的效率分别提高了 70%±8%、47%±5% 和 66%±6%。我们的工作促进了对有机异质界面激子和极化子动力学的物理理解，为实际设备中与 Inf. EPQ 相关的问题提供了普遍适用的解决方案。