Erbium-Anchoring Surface Engineering Enables Dual-Shell Stabilized CsPbI3 Quantum Dots for Efficient Pure-Red Light-Emitting Diodes

Small-sized CsPbI3 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 (Er3+) to enhance QD stability and suppress defects, in which Er3+ 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.