Stabilizing Perovskite Light-Emitting Diodes by Incorporation of Binary Alkali Cations
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 (FAPbI3 )-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 FAPbI3 -based PeLEDs during operation is directly associated with ion migration, and incorporation of binary alkali cations, i.e., Cs+ and Rb+ , in FAPbI3 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 externa...Continue Reading
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