The outstanding performance of halide perovskite makes it one of the champion materials for applications in optoelectronic devices. However, the stability of perovskites limits their practical applications. Among all the factors influencing the stability of perovskites, defects are one of the key factors. Till now, many chemical methods have been proposed to passivate defects. Nevertheless, there is still a lack of in situ passivation methods without the change of the composition of perovskites. Here, it is found that the external electric field can passivate the defects in FPEA₂PbI₄ (FPEAI = 2-(4-Fluorophenyl)ethylamine Hydroiodide) film in a capacitive device at 78 K, and the PL intensity can be enhanced greatly. A “charge-soaking effect” can be observed, that is PL intensity continues to increase for a long time after removing the electric field. Besides the emission peak from free exciton, two other peaks at the lower energy side from defect-bound excitons are observed. They are more susceptible to the external electric field than the free exciton. This work will deepen the understanding of exciton behavior and the interaction of electric field with excitons in two–dimensional (2D) hybrid perovskites for efficient light–emitting diodes (LEDs) and electrically pumped lasers. It provides a new in situ passivation method of perovskites for practical applications.

中文翻译：

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外电场原位钝化二维钙钛矿

卤化物钙钛矿的优异性能使其成为光电器件应用的冠军材料之一。然而，钙钛矿的稳定性限制了其实际应用。在影响钙钛矿稳定性的所有因素中，缺陷是关键因素之一。到目前为止，已经提出了许多化学方法来钝化缺陷。尽管如此，仍然缺乏不改变钙钛矿成分的原位钝化方法。在此发现，在78 K下，外部电场可以钝化电容器件中的FPEA ₂ PbI _{4 (FPEAI = 2-(4-氟苯基)乙胺氢碘化物)薄膜中的缺陷，并且PL强度可以大大增强。}可以观察到“电荷浸泡效应”，即去除电场后PL强度在很长一段时间内持续增加。除了自由激子的发射峰之外，还观察到来自缺陷束缚激子的较低能量侧的另外两个峰。它们比自由激子更容易受到外部电场的影响。这项工作将加深对二维（2D）混合钙钛矿中激子行为以及电场与激子相互作用的理解，用于高效发光二极管（LED）和电泵浦激光器。为实际应用提供了一种新的钙钛矿原位钝化方法。