Enhanced Operational Stability of Perovskite Light-Emitting Devices Through Differential Ion Motion

Hybrid perovskites are emerging as highly efficient materials for optoelectronic applications. However, their operational lifetime has remained a limiting factor for their continued progress. In thin-film perovskite light-emitting devices, ionic redistribution may distort the perovskite crystal structure, lowering conductivity and light emission due to the formation of vacancies and other traps. Our strategy for enhanced lifetimes involves producing differentiated ion motion within a device with a rational materials blend. The materials selectively move additive ions while restricting the transport of perovskite ions. To accomplish differentiated ion transport with optimal thin-film morphology, we combine a perovskite, a polyelectrolyte such as poly(ethylene oxide), and a salt additive such as LiPF₆. The added mobile Li⁺ and PF₆⁻ ions redistribute more favorably than the intrinsic ionic species and largely preserve the inherent structure of the perovskite film. At 0.5 wt% LiPF₆, CsPbBr₃ devices exhibit 100 h operation at more than 800 cd/m² under constant current driving, achieving a maximum luminance of 3260 cd/m². Incorporating zero-dimensional perovskite nanocrystals into these devices enhances the lifetime further to a luminance half-life of 129 h at 1530 cd/m², extrapolating to over 10,000 h at display luminance. We rationalize these findings through optical spectroscopy, impedance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray diffraction.