Multi-site Coordination Based on Macrocyclic Valinomycin for Efficient Defect Passivation and Crystal Regulation in Quasi-2D Perovskite Light-Emitting Diodes.

Quasi-two-dimensional perovskites have attracted increasing attention owing to their high exciton binding energy and efficient radiative recombination enabled by the multiple-quantum-well structure. Nevertheless, they still face critical challenges, including a high density of defect states and poor operational stability, which hinder further practical applications. Herein, we rationally introduce macrocyclic valinomycin (VO) as a multifunctional additive to simultaneously regulate defect states and crystallization of quasi-2D CsPbBr3 perovskites. VO features a well-defined three-dimensional cavity and a dense array of oxygen-rich functional groups. These structural attributes simultaneously passivate uncoordinated Pb2+ defects via coordination and stabilize the perovskite lattice through N-H···Br hydrogen bonding, thereby regulating crystallization and suppressing non-radiative recombination. The resulting VO-modified light-emitting diodes achieve a maximum luminance of 33,001 cd m-2 and an external quantum efficiency (EQE) of 22.83%, and a 1.5-fold improvement in operational lifetime. This work reveals the synergistic mechanism of macrocyclic molecules in defect passivation and crystal orchestration, offering new insights for molecular design in high-performance perovskite optoelectronics.