Core–Shell Ag-In-Zn-Ga-S@AgGaS2 Quantum Dots for 465 Nm Pure Blue Emission

Low-toxicity quantum dots (QDs) based on group I-III-VI elements have attracted significant interest due to their color-tunability for wide-gamut displays. Nevertheless, the width of the blue-emitting peak remains considerably broader than those of the green and red counterparts, resulting in degraded color purity, restricted gamut coverage, and diminished energy efficiency in blue-emitting devices. Here, we report spectroscopically pure blue QDs (λ = 465 nm) with an ultranarrow FWHM of 36 nm, achieving excellent color purity for blue-emitting I-III-VI QDs. Employing a two-step hot-injection method with precise thickness control, this approach enables epitaxial growth of an atomically thin 0.35 nm thick AgGaS 2 (AGS) shell on Ag-In-Zn-Ga-S cores. Using in situ HRTEM on systematically synthesized AIZGS@AGS architectures, we directly captured the controlled epitaxial growth of this shell, revealing a clean core–shell interface. The high-crystallinity AGS shell passivates surface defects, narrowing the PL spectrum from 103 to 36 nm. Moreover, systematic In:Zn ratio tuning further affords AIZGS@AGS QDs that exhibit narrow linewidths and continuous spectral coverage across the blue region (465–509 nm). Our study provides an effective approach for high-quality I-III-VI blue QDs, demonstrating significant potential for advanced display applications.