Core–Shell Ag‐In‐Zn‐Ga‐S@AgGaS 2 Quantum Dots for 465 Nm Pure Blue Emission

ABSTRACT 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.