Revealing the Self-Assembly Behavior of CsPbBr3 Nanoscale Supercrystals Mediated by Packed Clusters

Surface passivation ligands play a central role in optimizing binding interactions and inter-NC spacing and promoting the effective assembly of NC clusters and hierarchical superstructures. Here, we report a ligand-assisted assembly strategy that depends on quaternary ammonium salts and L-type ligands as an assembly driving force to optimize the interactions between QDs, thus contributing substantially to the formation of ordered CsPbBr3 nanoscale supercrystals (nano-SCs). Studies of structure characterization and small-angle X-ray scattering reveal that, initially, CsPbBr3 SC clusters are assembled into ordered nano-SCs. With the assistance of different L-type ligands, loose SC clusters are transferred into packed SC clusters. More importantly, only SC clusters driven by the cooperative interactions of ligand interdigitation and hydrogen bonds mediated the formation of nano-SCs. Their assembly driving force is systematically demonstrated through the surface states. The relationship between optical properties and assembly structures is discussed in relation to exciton binding energy, photoluminescence red-shift and nonradiative relaxation. Designing different types of ligands provides a new avenue to further study the self-assembled perovskite.