Forozi Sowmeeh Paria, Zohorfazeli Mohammad, Yazdani Elnaz
Department of Physics, Faculty of Basic Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran.
Sci Rep. 2023 Sep 20;13(1):15643. doi: 10.1038/s41598-023-42933-1.
Despite the rapid progress demonstrated in the efficiency of Perovskite light-emitting diodes (PeLEDs) in the past few years, ion migration has challenged the practical applications of these devices with undesirable hysteresis and degradation effect. Mobile ions in PeLEDs induced many unique and fast transient phenomena occurring on the time scale of microseconds to seconds and it is still far from clear how the underlying physical mechanism of ion motion-induced variation relates to the device performance. Therefore, in this work, we employ an ionic Drift-Diffusion Model (DDM) to evaluate measuring transient current response in a time scale of sub-seconds. The results show that spatial redistribution of ions within the perovskite results in dynamic electric field variation, which in turn, affects charge carrier injection and distribution. Moreover, the time delay between anion and cation migration leads to an unequal rate of charge carrier injection, hence the multi-stage behavior of the current-time response. It is also realized that the potential barrier of charge injection due to cation and anion accumulation at perovskite interfaces with electron and hole transporting layers reduces. Therefore, the facilitation of charge injection favors radiative recombination, and improved IQEs are expected at higher ion densities. It is found that the current-time response of the device gives beneficial information on cation and anion migration time scales. Choosing an appropriate scan rate in accordance with cation-related slow migration time is the first step to achieving reliable measurement procedures and hysteresis-free PeLED.
尽管在过去几年中钙钛矿发光二极管（PeLEDs）的效率取得了快速进展，但离子迁移以不良的滞后和降解效应挑战了这些器件的实际应用。PeLEDs中的移动离子引发了许多独特且快速的瞬态现象，这些现象发生在微秒到秒的时间尺度上，而离子运动引起的变化的潜在物理机制与器件性能之间的关系仍远未明确。因此，在这项工作中，我们采用离子漂移扩散模型（DDM）来评估在亚秒时间尺度内测量瞬态电流响应。结果表明，钙钛矿内离子的空间重新分布导致动态电场变化，进而影响电荷载流子的注入和分布。此外，阴离子和阳离子迁移之间的时间延迟导致电荷载流子注入速率不等，从而产生电流 - 时间响应的多阶段行为。还认识到，由于阳离子和阴离子在与电子和空穴传输层的钙钛矿界面处积累而导致的电荷注入势垒降低。因此，电荷注入的促进有利于辐射复合，并且在更高的离子密度下有望提高内部量子效率（IQEs）。发现器件的电流 - 时间响应给出了有关阳离子和阴离子迁移时间尺度的有益信息。根据与阳离子相关的缓慢迁移时间选择合适的扫描速率是实现可靠测量程序和无滞后PeLED的第一步。
