Aqueous Colloidal Perovskite Quantum Emitters

Abstract Aqueous solutions of nanoparticles are the cornerstones for applications in diagnostics, catalysis and more, where control over the nanoparticle's dispersion is pivotal to tailoring the final product properties. Of late, halide perovskite nanocrystals (HPNCs) with outstanding optoelectronic properties emerge as a class of semiconductor nanocrystals distinct from the incumbents. However, HPNCs are particularly susceptible to moisture induced degradation, limiting their utility and regulation in aqueous environments. Here, this hurdle is overcome to realize stable, mono‐disperse, highly emissive HPNCs in aqueous environments even under ultra‐dilute conditions. These colloidal HPNCs are synthesized via a facile room‐temperature structural transformation‐induced in situ core‐shell self‐assembly mechanism in contrast to the widely used pre‐core‐shell approach. The green HPNCs exhibit >80% photoluminescence quantum yield (PLQY) with excellent water dispersion stability (i.e., zeta potential >80 mV) even after >10,000 h in water. Unprecedented aqueous solution phase single‐photon emission with g (2) (0) <0.2 at concentrations as low as ≈0.1 n M is measured. These aqueous HPNCs offer full color tunability that covers the entire Rec. 2020 standard. These findings will lay the foundation for innovative applications of HPNCs in aqueous environments, unlocking new opportunities for nanoscale sensing and optofluidics in photonics, environmental science, and materials engineering.