Soft‐Lattice Directed CsPb(Br/I) 3 Quantum Dots Ligand Design for High‐Performance Pure‐Red Electroluminescence

Mixed‐halide CsPb(Br/I) 3 quantum dots (QDs) are essential for Rec.2020‐compliant displays but suffer from instability due to their soft ionic lattice. Conventional ligand design prioritizes high adsorption energy and overlooks local electronic perturbations. Here we demonstrate that adsorption strength alone fails to predict surface stability and device performance. We reveal that strong local electron donation from ligand groups to metal atoms on the QDs' surface induces excessive ligand‐to‐metal charge transfer (LMCT), which in turn triggers Pauli repulsion and electrostatic screening, thereby weakening adjacent Pb─I bonds and leading to lattice collapse despite the relatively high adsorption energy of ligands. We propose a “locally weak but globally strong” (LWGS) coordination strategy to balance robust anchoring with lattice integrity. Using tauramide hydrochloride (TAH) with a locally weak electron‐donating sulfonyl coordination group and globally strong multidentate binding, the TAH‐treated QDs exhibit suppressed nonradiative recombination, enhanced stability, and superior electroluminescent performance, delivering a peak external quantum efficiency (EQE) of 28.9% and excellent spectral stability. The devices achieve an operational half‐lifetime (T 50 ) of 62.8 h at 100 cd m −2 , with a 638 nm emission closely matching the Rec.2020 pure‐red standard. This LWGS principle establishes a transformative guideline for ligand design to stabilize soft‐lattice perovskites toward high‐performance optoelectronics.