Pure green emission in InP-based QLEDs via ZnSeS interlayer for enhanced electron confinement

Quantum dot light-emitting diodes (QLEDs) are promising for next-generation near-eye displays, yet achieving Rec. 2020-compliant green emission remains challenging due to insufficient electron confinement and field-induced spectral redshift in InP-based quantum dots (QDs). Here, we report a band-engineering strategy by introducing a compositionally graded ZnSeS interlayer between ZnSe and ZnS shells to construct a stepwise conduction band potential. This design effectively enhances electron confinement, suppressing inter-shell delocalization and mitigating the quantum-confined Stark effect. The resulting QDs exhibit pure green emission at 528 nm with a narrow full width at half maximum of 37 nm and a high photoluminescence quantum yield of 95%. QLED devices based on these QDs show a significantly reduced field-induced redshift of only 6 nm, with a stable electroluminescence peak at 534 nm, a maximum external quantum efficiency of 13.2%, a peak luminance of 72 252 cd m^-2, and an operational lifetime (T₅₀) of 21 683 h at 100 cd m^-2. A large-area device (2 × 2 cm²) maintains a high efficiency of 12.8%, demonstrating excellent scalability. Furthermore, high-resolution QLED arrays exceeding 8000 PPI are achieved via capillary-bridge-assisted patterning, enabling static electroluminescent displays. This work provides a feasible pathway for the realization of wide-gamut Cd-free QLED displays.