Thermal/Water‐Stable CsPbX 3 @SiO x Core–Shell Quantum Dots for Inkjet Printing and Potential Color Converting Applications

Abstract Ligand‐mediated surface passivation is widely used to fill defect sites and stabilize perovskite nanoparticles, keeping their photophysical properties unchanged. However, this strategy can promote the growth of agglomerates, quenching the luminescence of nanoparticles. Additionally, the presence of bulky ligands can hinder the interparticle carrier transport, difficulting the fabrication of efficient optoelectronic devices. In this work, the synthesis of SiO x ‐covered CsPbX 3 PQDs (CsPbX 3 @SiO x ) is performed through a modified ligand‐assisted reprecipitation method (LARP), by adding 3‐aminopropyl‐triethoxysilane (APTES) and oleic acid to the mixture reaction. Here, it is possible to suppress the aggregates formation, achieving water‐stable single core–shell PQDs with a photoluminescence quantum yield of up to 99.4% and facile bandgap modulation by varying the halide content. Accordingly, CsPbX 3 @SiO x PQDs inks are obtained for preparing inkjet‐printed QR codes and color converters, with stable luminescence up to 1.5 and 9 h of continuous operation at 2.5 V for Cl/Br‐ and Br‐perovskites, respectively. Interestingly, a PL splitting is observed for the Br/I‐perovskite along the time, indicating the emergence of halide migration to generate Br‐ and I‐rich domains, mediating the generation of white color emission. This contribution offers a prominent alternative to producing single PQDs with suitable optical properties and stability for developing promising LED technologies.