Decoupling the Positive and Negative Aging Processes of Perovskite Light-Emitting Diodes Using a Thin Interlayer of Ionic Liquid.

A positive aging phenomenon, that is, enhancement of the electroluminescence performance at the beginning of electrical aging, is commonly observed for the state-of-the-art perovskite light-emitting diodes (PeLEDs). The origins of positive aging could fundamentally interfere with those of the operational deterioration processes of PeLEDs (namely negative aging), bringing difficulty in analyzing the degradation mechanisms. This work decouples the positive and negative aging processes of PeLEDs by inserting a thin ionic liquid interlayer between the hole-injection layer and the perovskite layer. This interlayer inhibits ions migration by passivating the halogen vacancies of perovskite films and suppresses interfacial exciton quenching, enabling us to decouple the positive and negative aging processes of PeLEDs while increasing the device efficiency. Inserting an ionic liquid interlayer is also demonstrated to be effective for iodide-based PeLEDs and applicable with the use of other ionic liquids. Our work provides an ideal system for fundamental studies on the degradation mechanisms of PeLEDs.