Multi‐Site Anchoring for Tilted Octahedral Structure Stability Toward Efficient Blue Perovskite LEDs

The [PbX 6 ] 4− octahedron, while serving as the fundamental building block in perovskites and endowing exceptional photoelectric properties, exhibits inherent molecular softness and structural distortion that led to dynamic instabilities. Notably, the collapse of lead‐halide octahedra triggered by halide vacancies presents a critical challenge to stability and performance, particularly in mixed‐halide perovskite systems. Herein, we demonstrate a molecular engineering strategy using alkali metal trifluoromethanesulfonate additives, which are proposed to stabilize the perovskite lattice via a multi‐anchoring mechanism. The sulfonyl oxygen groups are believed to interact with under‐coordinated Pb sites, while the alkali metal cations are suggested to associate with halide species at the crystal surface, collectively mitigating octahedral distortion. This cooperative stabilization is supported by enhanced phase purity, suppressed nonradiative recombination, and improved optical performance in quasi‐2D perovskite films. Consequently, the optimized perovskite films exhibit superior blue emission characteristics with a high photoluminescence quantum yield (PLQY) of 65.32%. The resultant blue PeLEDs deliver an external quantum efficiency (EQE) of 15.60% at 487 nm with a device lifetime of 220 min, representing a competitive performance compared with state‐of‐the‐art blue PeLEDs in this spectral range. This work establishes octahedral stabilization as a fundamental design principle for advancing high‐performance perovskite optoelectronic devices.