Performance Enhancement of Quasi-Two-Dimensional Perovskite Light-Emitting Diodes by Constructing an Efficient Energy Funnel via Ionic Liquid Doping

Ionic liquids are effective additives to enhance the performance and stability of perovskite optoelectronic devices. Because of the diverse types of ionic liquids, their role for device improvement, especially in perovskite light-emitting diodes (PeLEDs), still needs to be investigated. To answer this question, we studied the performance of quasi-two-dimensional (quasi-2D) PeLEDs doped with two different kinds of ionic liquids, BMIMBF4 and BMIMBr. Our results show that the optimization of the PeLED performance arises from the modification of the crystallization process of quasi-2D perovskite films. After doping with the ionic liquid, the distribution of the low-dimensional perovskite phases becomes gradient. This gradient phase distribution forms an energy funnel, which could boost the charge transfer and facilitate the luminescence efficiency. Further comparative investigation shows that the BF4– anion is more effective than Br– in the optimization of the crystallization process. These results provide better understanding of the role of anions in ionic liquid additives and the ways to enhance the performance of perovskite light-emitting devices.