Control on the long-range ordering of perovskite nanocrystal superlattices via thermal regulation of nanoconfined water

Abstract

Perovskite nanocrystal superlattices (SLs) provide a route to collective optical properties, but controlling their formation directly in liquid media remains challenging because nanocrystal growth, ligand-mediated assembly, and ordering occur simultaneously. Here, temperature-dependent CsPbBr₃ nanocrystal SL formation was investigated in a bis(2-ethylhexyl) sulfosuccinate/water/ligand system. At 90 and 110 °C, uniform nanocube building blocks assembled into ordered SLs, whereas higher temperatures produced anisotropic nanoplatelets, irregular assemblies, or dispersed nanocrystals. The SL domains formed at 90 °C were larger but less abundant, while those formed at 110 °C were smaller and more abundant. Liquid-phase small-angle X-ray scattering measurements and molecular dynamics simulations suggest that temperature alters water retention and water localization within ligand-rich environments, thereby influencing both nanocrystal growth and subsequent assembly. The ordered SLs exhibited distinct photoluminescence behavior and were further processed into luminescent anti-counterfeiting patterns. These results highlight temperature as a practical handle for controlling perovskite nanocrystal SL formation in nonpolar liquid media.