Simultaneous Improvement in Blue-Light Emission and Operational Stability of Nanometer-Thick Perovskite Light-Emitting Diodes by Incorporating Multiple Organic/Inorganic Chloride Salts

Although recent advancements in organic–inorganic hybrid perovskites have captivated not only the community of photovoltaics but also the field of display technologies, the development of perovskite-based light-emitting diodes (PeLEDs) with pure-blue emission has lagged behind that of their green- or red-emitting counterparts in terms of optoelectronic properties and operational stability. In this study, we report a comprehensive strategy to enforce pure-blue emission of PeLEDs with high quantum efficiency and operational stability by introducing multiple cationic chlorides in perovskite layers. First we demonstrate the gradual induction of a distinct hypsochromic shift to the blue region in green-emissive CsFAPbBr3 perovskite films by incorporating bulky ammonium bromide and chloride. This shift is accomplished through dimensional and lattice structure engineering. Second, small A-site cationic chlorides are introduced to further tune the band gap and optoelectronic properties of the pure-blue PeLEDs. Finally, yttrium(III) chloride is introduced as an additive to hamper severe phase segregation and ion migration in the perovskite emitting layers. As a result of these deliberate modifications, the proper inclusion of multiple inorganic chloride salts enforced the hypsochromic shift of the perovskite layer with a minimized defect density, leading to pure-blue electroluminescence at 472 nm with an exceptionally narrow bandwidth of 17.91 nm and an external quantum efficiency of 4.22%. The optimized chlorides also achieve superior operational stability with an electroluminescence half-life of 23 min at an initial luminance of 350 cd/m2 in an ambient atmosphere. This suggests a straightforward way to prepare practical pure-blue PeLEDs for achieving full-color perovskite display technologies.