Regulating the continuous and concentrated distribution of Quasi-2D perovskite phases to achieve Sky-Blue Light-Emitting diodes with efficiency approaching 17

•The BEABr organic ligand is used for phase regulation and radiation recombination.•Halogen-halogen bonding can effectively enhance interlayer interactions.•The emission of pure bromide perovskites is tuned from green to blue.•Highly efficient and spectrally stable sky-blue PeLEDs are achieved. Blue perovskite light-emitting diodes (PeLEDs) are increasingly crucial for manufacturing high-definition full-color displays due to their outstanding electroluminescent properties. Quasi-two-dimensional (quasi-2D) perovskite stands out as the most promising material for blue light-emitting layer, given its robust quantum/dielectric confinement. In this study, we present the preparation of PeLEDs with a tunable blue emission wavelength using pure bromide perovskite components by adjusting the content of halogenated organic ammonium bromide [2-bromoethylamine hydrobromide (BEABr)]. The bifunctional ligand BEABr not only achieves an excellent phase distribution of quasi-2D perovskite but also reduces the weak van der Waals gap between individual perovskite layers, facilitating effective energy transfer in perovskite films. Additionally, the bifunctional groups passivate perovskite defects and inhibit phase separation, leading to efficient and stable sky-blue luminescence. The BEABr-doped sky-blue PeLED demonstrated superior device performance, achieving a maximum external quantum efficiency of 16.98 % at 493 nm. This work serves as inspiration for further exploration of efficient and stable commercial blue PeLED devices.