Suppression of phase segregation in red CsPbIBr2-based perovskite LECs/LEDs: impact of Mn doping, crystallization control, and grain passivation†

Abstract

As alternatives to conventional perovskite light-emitting diodes, perovskite light-emitting electrochemical cells (PeLECs) are in great demand in modern science and technology due to their simplified structure and attainable higher luminance. Here, for the first time, we present the implementation and characterization of red CsPbIBr₂-based PeLECs/LEDs. To improve perovskite material phase stability, we applied the following strategies for mitigating the mixed anion lead halide perovskite phase segregation: Pb²⁺ partial substitution by Mn²⁺, boundary passivation by poly(ethylene oxide) with polyvinylidene fluoride, and two-step thermal treatment with vacuuming and annealing. The complex measurements of photoluminescence, optical density, energy-dispersive X-ray spectroscopy, and X-ray diffraction confirm the minor phase segregation in the optimized perovskite layers. The performed ab-initio calculations predicted the band gaps of perovskite materials with a mixed anion composition, corresponding well to the results of optical measurements. Finally, current and electroluminescence time tracking proved the formation of a dynamic p–i–n structure in the studied PeLEC devices. The developed PeLECs/LEDs exhibited relatively high, for red PeLECs, electroluminescence up to 96 cd m⁻² with a peak position at 667–672 nm.