Surface Defects Passivation of ZnSeTe/ZnSe/ZnS Quantum Dots by Iodine Ions for Highly Efficient Blue Light‐Emitting Diodes

The development of cadmium‐free blue quantum dots (QDs) is of paramount importance to the display industry. In this study, high‐quality ZnSeTe/ZnSe/ZnS blue QDs, followed by surface treatment with ZnI2 are initially synthesized. The introduction of ZnI2 passivated the surface defects, resulting in an increase in the fluorescence quantum yield. The time‐resolved photoluminescence (TRPL) demonstrates a significant inhibition of non‐radiative recombination associated with the surface defect state. The density functional theory (DFT) calculation reveals that the binding energy between iodine ions and zinc ions is higher than that between oleate ions and zinc ions, providing a theoretical basis for the effective passivation of the suspended bonds of zinc ions on QDs' surface by iodine ions. Moreover, quantum dot light‐emitting diodes (QLEDs) are fabricated and UV photoelectron spectra (UPS) indicate the hole injection barrier between the hole transport layer and QDs decreases 0.12 eV after QDs being treated by ZnI2, facilitating hole injection. Finally, The ZnI2‐treated QLED demonstrates a 1.57‐fold and 1.82‐fold improvement in Lmax and EQEmax, respectively, reaching 6370 cd m−2 and 9.1%, compared to the pristine QLED. The work serves as a valuable reference for enhancing the performance of cadmium‐free blue QLED.