Stabilizing Perovskite Light‐Emitting Diodes by Incorporation of Binary Alkali Cations
Nan Li, Lei Song, Yongheng Jia, Yifan Dong, Fangyan Xie, Liduo Wang, Shuxia Tao, Ni Zhao
Abstract
Abstract The poor stability of perovskite light‐emitting diodes (PeLEDs) is a key bottleneck that hinders commercialization of this technology. Here, the degradation process of formamidinium lead iodide (FAPbI 3 )‐based PeLEDs is carefully investigated and the device stability is improved through binary‐alkalication incorporation. Using time‐of‐flight secondary‐ion mass spectrometry, it is found that the degradation of FAPbI 3 ‐based PeLEDs during operation is directly associated with ion migration, and incorporation of binary alkali cations, i.e., Cs + and Rb + , in FAPbI 3 can suppress ion migration and significantly enhance the lifetime of PeLEDs. Combining experimental and theoretical approaches, it is further revealed that Cs + and Rb + ions stabilize the perovskite films by locating at different lattice positions, with Cs + ions present relatively uniformly throughout the bulk perovskite, while Rb + ions are found preferentially on the surface and grain boundaries. Further chemical bonding analysis shows that both Cs + and Rb + ions raise the net atomic charge of the surrounding I anions, leading to stronger Coulomb interactions between the cations and the inorganic framework. As a result, the Cs + –Rb + ‐incorporated PeLEDs exhibit an external quantum efficiency of 15.84%, the highest among alkali cation‐incorporated FAPbI 3 devices. More importantly, the PeLEDs show significantly enhanced operation stability, achieving a half‐lifetime over 3600 min.