Colloidal quantum-dot light-emitting diodes (QLEDs) are lucrative options for color-pure lighting sources. To achieve high-performance QLEDs, besides developing high-efficiency quantum dots (QDs), it is essential to understand their device physics. However, little understanding of the QD emission behavior in active QLEDs is one of the main factors hindering the improvement of device efficiency. In this work, we systematically studied the exciton dynamics of gradient composition [email protected] QDs during electroluminescence in a working QLED. With time-resolved photoluminescence analyses using fluorescence lifetime imaging microscopy we analyzed a large population of QDs spatially spreading over an extended area inside and outside the device. This allows us to reveal the statistically significant changes in the behavior of QD emission in the device at different levels of applied voltages and injection currents. We find that the QD emission efficiency first drops in device fabrication with Al electrode deposition and that the QD exciton lifetime is then statistically reduced further under the QLED’s working conditions. This implies the nonradiative Auger recombination process is active in charged QDs as a result of imbalanced charge injection in a working QLED. Our results help to understand the exciton behavior during the operation of a QLED and demonstrate a new approach to explore the exciton dynamics statistically with a large QD population.

中文翻译：

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有源器件操作下的胶体量子点LED的激子动力学

胶体量子点发光二极管（QLED）是纯色光源的有利之选。为了实现高性能的QLED，除了开发高效的量子点（QD）外，还必须了解它们的器件物理原理。然而，对有源QLED中QD发射行为的了解很少，这是阻碍器件效率提高的主要因素之一。在这项工作中，我们系统地研究了工作的QLED在电致发光过程中梯度成分[受电子邮件保护的] QD的激子动力学。通过使用荧光寿命成像显微镜的时间分辨光致发光分析，我们分析了一大批QD，这些QD在空间上分布在设备内部和外部的扩展区域中。这使我们能够揭示出在不同水平的施加电压和注入电流下，器件中QD发射行为的统计学显着变化。我们发现在铝电极沉积的器件制造过程中，QD发射效率首先下降，然后在QLED的工作条件下，QD激子寿命进一步降低。这意味着由于工作QLED中电荷注入的不平衡，带电QD中非辐射俄歇复合过程是活跃的。我们的结果有助于了解QLED运作过程中的激子行为，并展示了一种新的方法来统计地研究具有大QD种群的激子动力学。我们发现在铝电极沉积的器件制造过程中，QD发射效率首先下降，然后在QLED的工作条件下，QD激子寿命进一步降低。这意味着由于工作QLED中电荷注入的不平衡，带电QD中非辐射俄歇复合过程是活跃的。我们的结果有助于了解QLED运作过程中的激子行为，并展示了一种新的方法来统计地研究具有大QD种群的激子动力学。我们发现在铝电极沉积的器件制造过程中，QD发射效率首先下降，然后在QLED的工作条件下，QD激子寿命进一步降低。这意味着由于工作QLED中电荷注入的不平衡，带电QD中非辐射俄歇复合过程是活跃的。我们的结果有助于了解QLED运作过程中的激子行为，并展示了一种新的方法来统计地研究具有大QD种群的激子动力学。