Highly Stable CsPbBr ₃ Nanoplatelets via Dual Short‐Chain Ligand Synergy for Deep‐Blue Light‐Emitting Diodes

Quantum‐confined perovskite nanoplatelets (NPLs) with ultra‐narrow emission linewidths represent promising blue‐emission materials for ultrahigh‐definition displays. However, their practical applications have been severely hindered by material instability and poor charge transport properties. Herein, we employed thioglycolic acid (TA) and anilinium bromide (AnHBr) as dual short‐chain ligands, successfully synthesizing monodisperse CsPbBr 3 NPLs with an emission peak at 463 nm and a remarkable photoluminescence quantum yield (PLQY) of 89%. This approach involves introducing TA into the perovskite precursor solution, where its carboxyl groups strongly coordinate with uncoordinated Pb 2+ on the surface to form TA‐modified NPLs (TA‐NPLs). Subsequently, the introduced Br − from AnHBr effectively fills existing Br − vacancies on initial NPLs’ surface to form TA‐ and AnHBr‐modified NPLs (TA+AnHBr‐NPLs). Both ligands enhance structural stability through strong interactions with the [PbBr 6 ] 4− octahedra. The resulting solution maintains stable blue emission when stored in air for 21 days and exhibits excellent photostability. The fabricated TA+AnHBr‐NPLs‐based light‐emitting diodes demonstrate efficient deep‐blue electroluminescence at 461 nm, with an external quantum efficiency (EQE) of 1.00%, CIE color coordinates of (0.146, 0.085), and remarkable spectral stability. This study offers a method for synthesizing high‐stability perovskite materials and further fabricating high‐performance devices.