Pure-halide　reduced-dimensional　perovskites,　featuring　large　exciton　binding　energy　and　tunable　bandgap,　show　great　potential　for　high-efficiency　deep-blue　perovskite　light-emitting　diodes　(PeLEDs).　However,　their　efficiency,　particularly　in　the　low　n-value　phase　domain　(＂n＂　represents　the　number　of　octahedral　sheets),　lags　behind　analogous　perovskite　emitters.　Herein,　it　is　demonstrated　that　the　vibration　of　edge-dangling　octahedra　in　the　low　n-value　phase　activates　notorious　exciton-phonon　(EP)　coupling,　thereby　deteriorating　efficiency.　To　address　this　issue,　an　approach　is　reported　to　manage　edge-state　lattices　by　introducing　tris(4-fluorophenyl)　phosphine　(TFP)　ligands.　Attributed　to　the　large　steric　hindrance　of　TFP　ligands　and　their　strong　binding　affinity　for　edge-dangling　octahedra,　the　edged-octahedral　tilting　reconstruction　can　effectively　suppress　lattice　vibration　and　inhibit　EP　coupling.　This　strategy　yields　deep-blue　emitting　film　with　a　spectral　linewidth　of　21　nm　and　a　photoluminescence　quantum　yield　of　85%　at　low　excitation　densities.　The　resulting　PeLEDs　achieve　deep-blue　emission　at　469　nm,　with　a　maximum　luminance　of　2,428　cd　m-2　and　a　maximum　external　quantum　efficiency　of　10.4%,　marking　them　among　the　most　efficient　deep-blue　PeLEDs　reported.　The　strategy　also　showcases　universality　for　higher　n-value　reduced-dimensional　perovskites.　It　is　believed　that　the　observation,　along　with　the　edge-state　management　strategy,　lays　the　groundwork　for　further　advancements　in　reduced-dimensional　perovskite　optoelectronic　devices.