Mitigating Surface Energy and Core‐Shell Interface Strain of Yb 3+ ‐Doped ZnSe‐Based Quantum Dots for Pure‐Blue Emission QLED Devices

Abstract Large ZnSe quantum dots (QDs) with an emission peak ≈450 nm hold significant promise for display technologies. However, achieving efficient pure‐blue emission through the enlargement of ZnSe nanocrystals remains a significant challenge. In this study, a breakthrough is reported in growing large‐size ZnSe QDs well beyond the exciton Bohr radius through Yb 3+ doping strategy. Yb 3+ doping reduces the surface energy of the ZnSe (220) crystal plane and alleviates interface strain in the ZnSe/ZnS structure, enabling the QDs to grow larger while maintaining enhanced crystal stability. The resulting Yb: ZnSe/ZnS QDs exhibit pure‐blue emission at 453 nm, with a full width at half maximum (FWHM) of 46 nm and a high photoluminescence quantum yield (PLQY) of 67.5%. When integrated into quantum dot light‐emitting diodes (QLEDs), the devices display electroluminescence (EL) at 455 nm, with an external quantum efficiency (EQE) of 1.35%, and a maximum luminance of 1337.08 cd m −2 .