Halide ion migration suppression for spectrally stable pure-red perovskite nanocrystal electroluminescence

Perovskite nanocrystals (NCs) are promising for high-definition display light-emitting diodes (LEDs), particularly for pure red emission (620-650 nm) via mixed-halide CsPbI_3-xBr_x systems. However, severe halide migration under electric fields induces irreversible phase separation, degrading spectral stability and electroluminescence efficiency. Herein, we report an in-situ ligand coordination strategy to suppress halide ion migration using tris(1-chloro-2-propyl) phosphate (TCPP), thereby achieving stable electroluminescence of pure-red CsPb(Br/I)₃ perovskite NCs. Endowed with dual active sites (phosphoryl groups and chloride ions), TCPP can form robust interfacial bonding with pure-red perovskite NCs via PO groups and Cl sites. This dual-site synergistic interaction not only effectively passivates surface defects and reduces nonradiative recombination but also constructs a dense ion barrier layer, directly inhibiting the migration and segregation of halide ions at the surface and interfaces. Benefiting from this synergistic effect, the fabricated perovskite NC light-emitting diodes (PeLEDs) exhibit stable pure-red emission at 650 nm with a maximum external quantum efficiency (EQE) of 24.62%. This work establishes the critical role of dual-active-site ligands in suppressing halide ion migration, providing a facile and effective strategy for the fabrication of spectrally stable pure-red perovskite NC electroluminescent devices.