Erbium-Anchoring Surface Engineering Enables Dual-Shell Stabilized CsPbI Quantum Dots for Efficient Pure-Red Light-Emitting Diodes.

Small-sized CsPbI quantum dots (QDs) are promising emitters for pure-red perovskite light-emitting diodes (PeLEDs), yet their surface instability and defect formation hinder practical applications. Herein, we propose a surface doping strategy using erbium (Er) to enhance QD stability and suppress defects, in which Er ions anchor to the QD surface via strong coordination with surface iodide and oleic acid, forming a robust organic-inorganic dual-shell coordination structure that significantly inhibits undesirable degradation and Oswald ripening throughout the synthesis and purification processes. The Er-doped QDs (Er-QDs) deliver higher color purity with pure-red emission, near-unity photoluminescence quantum yield, and enhanced charge transport. Consequently, PeLEDs based on Er-QDs achieve a peak external quantum efficiency over 25% with stable emission (Commission on Illumination (CIE) 0.708, 0.292), meeting the Rec.2020 standard even under high driving voltages. This work offers a viable surface engineering strategy to stabilize perovskite QDs, enabling their application in high-performance optoelectronic devices.