Electric field induced degradation in sky-blue perovskite light-emitting diodes. (October 2022) - Sun, Shuang-Qiao
Abstract: A common strategy to obtain blue- or sky-blue-emitting perovskite light-emitting diodes (PeLEDs) is to incorporate chlorine into the bromine-based perovskites. However, reliability is a crucial and challenging issue. The underlying degradation mechanism of these mixed-halide PeLEDs under continuous electrical bias remains incompletely understood. We unveil that electrical bias can seriously influence the spectral stability and efficiency roll-off of mixed-halide PeLEDs. Through the comprehensive microscopic and spectroscopic studies, we identify several key factors that account for the device degradation: (i) electric-field induced Joule heating; (ii) pinhole formation under electrical bias; and (iii) halogen ion migration toward the interface of electron-transport layer and cathode. We also substantiate that chloride ion migration plays a more dominant role than bromide in the device degradation of the sky-blue mixed-halide PeLEDs. The experimental results are fully supported by our theoretical calculations. These findings provide new insights for a deep understanding of the degradation mechanism of the mixed-halide PeLEDs and pave the way to obtaining stable PeLEDs based on compositional engineering strategies in the future. Graphical abstract: Image 1 Highlights: Phase instability mechanism of the mixed-halide perovskite. Chloride-dominated migration leads to sky-blue LEDs degradation. Critical role of perovskite/ETL interface on the device stability.