Dual-Mode Strain Relief via Zinc Acetate Enables High-Efficiency InP Quantum Dot Light-Emitting Diodes

Heteroepitaxial shell growth on quantum dots (QDs) is essential for tailoring carrier dynamics but is often hampered by core-shell interface strain, which becomes more prominent in environmentally friendly InP QDs due to their significant size effect. Although post-treatment of InP cores with zinc compounds is a common approach to alleviate interface strain, conventional synthesis methods often fail to achieve effective doping, typically leaving zinc on the core surface rather than within the lattice. Herein, we present a dual-mode strain relief strategy using the small-molecule precursor Zn(Ac)₂. Its ionic bonding character and low steric hindrance enable efficient Zn doping into the InP core and promote uniform epitaxial shell growth, leading to a 50% reduction in interfacial strain and a near-unity photoluminescence quantum yield in InP QDs. This approach simultaneously addresses two major sources of strain: lattice mismatch between the core and shell and steric hindrance from bulky surface ligands. The fabricated green InP-based QLED achieved a high external quantum efficiency of 26.3% and a current efficiency of 108.3 cd A^-1. We believe this strategy provides a general and scalable strain engineering platform for QDs, with broad applicability across various material systems.