Despite quick development of perovskite light‐emitting diodes (PeLEDs) during the past few years, the fundamental mechanisms on how ion migration affects device efficiency and stability remain unclear. Here, it is demonstrated that the dynamic redistribution of mobile ions in the emissive layer plays a key role in the performance of PeLEDs and can explain a range of abnormal behaviours commonly observed during the device measurement. The dynamic redistribution of mobile ions changes charge–carrier injection and leads to increased recombination current; at the same time, the ion redistribution also changes charge transport and results in decreased shunt resistance current. As a result, the PeLEDs show hysteresis in external quantum efficiencies (EQEs) and radiance, that is, higher EQEs and radiance during the reverse voltage scan than during the forward scan. In addition, the changes on charge injection and transport induced by the ion redistribution also well explain the rise of the EQE/radiance values under constant driving voltages. The argument is further rationalized by adding extra formamidinium iodide (FAI) into optimized PeLEDs based on FAPbI₃, resulting in more significant hysteresis and shorter operational stability of the PeLEDs.

中文翻译：

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钙钛矿型发光二极管中移动离子的动态重新分布

尽管钙钛矿发光二极管（PeLED）在过去几年中得到了快速发展，但是关于离子迁移如何影响器件效率和稳定性的基本机制仍不清楚。在此证明，在发射层中移动离子的动态重新分布在PeLED的性能中起着关键作用，并且可以解释在设备测量期间通常观察到的一系列异常行为。流动离子的动态重新分布会改变载流子注入，并导致重组电流增加。同时，离子的重新分布也会改变电荷的传输并导致分流电阻电流减小。结果，PeLED在外部量子效率（EQE）和辐射率方面表现出滞后现象，也就是说，反向电压扫描期间的EQE和辐射比正向扫描期间更高。此外，离子重新分布引起的电荷注入和输运的变化也很好地解释了恒定驱动电压下EQE /辐射率值的升高。通过在基于FAPbI的优化PeLED中添加额外的碘化甲酰胺（FAI），可以进一步合理化该论点_{如图3所示}，导致PeLED的更大的滞后和更短的操作稳定性。