Surface Chemistry of All Inorganic Halide Perovskite Nanocrystals: Passivation Mechanism and Stability

All inorganic halide perovskite (IHP) nanocrystals (NCs) have emerged as a new class of optoelectronic materials for various applications. Surface ligands as surface passivators are essential components of nucleation and growth processes, photoluminescence quantum yields (PL QY), stability, and photoelectric applications. In this review, the relationship of perovskite structure modified is outlined by surface ligand and some properties on account of the ion structure features. This review specifically focuses on the roles of surface ligands in the construction of IHP NCs with fewer defects, higher PL QY, and better stability. Generally, ligands binding to the surface of IHP NCs can form passivation layer, which are beneficial to not only the improvement of PL QY by filling the Br- or Pb2+ vacancy but also the enhancement of stability. The surface passivation mechanisms are attributed to the [BrHN+] hydrogen-bonding, chelation, and dative covalent bond interactions. Furthermore, degradation mechanisms assigned to the hydration, ion migration, and dissociation are discussed. The equilibrium problem of purifying and QY and possible reasons are also addressed, which are believed to be solved in the near future with the help of coordination chemistry and surface engineering. Finally, a brief outlook including challenges and possible development is provided.