The efficiency improvement of organic light-emitting diodes (OLEDs) is important but challenging. Here, we introduce a unique OLED with a hole modulation layer (HML) in the middle of its emission layer (EML). The external quantum efficiency and power efficiency can be improved by approximately 58% when an HML with optimized thickness is inserted. HML insertion can efficiently retard hole flow, thus improving (i) exciton distribution uniformity and (ii) local electron–hole charge balance. A systematic study of the individual contributions of two EMLs separated by the HML shows that the former factor dominantly works at low current densities (< 10 mA/cm²), whereas the latter factor functions over the entire current density range of the OLED. Therefore, the efficiency improvement is greatest at low current densities, which aligns with the typical operating range in display applications. The results provide a deeper understanding of the OLED emission mechanism, and the proposed OLED structure can significantly benefit high-performance OLED displays.

Graphical Abstract

中文翻译：

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双发射层有机发光二极管中空穴和激子分布的调控

有机发光二极管（OLED）的效率提高很重要，但也具有挑战性。在这里，我们介绍了一种独特的 OLED，其发射层 (EML) 中间具有空穴调制层 (HML)。当插入厚度优化的HML时，外量子效率和功率效率可提高约58%。HML插入可以有效地延迟空穴流动，从而改善( i )激子分布均匀性和( ii )局部电子-空穴电荷平衡。对由 HML 分隔的两个 EML 的单独贡献进行的系统研究表明，前一个因素主要在低电流密度（< 10 mA/cm ²），而后一个因素在 OLED 的整个电流密度范围内起作用。因此，在低电流密度下效率提升最大，这与显示应用中的典型工作范围一致。这些结果让人们对OLED发光机制有了更深入的了解，并且所提出的OLED结构可以显着有利于高性能OLED显示器。

图形概要