1. Schematic diagram of passivation strategies for different ligands on the surface of CsPbX₃ nanocrystals

2. (a) Schematic diagram of instability mechanism of CsPbX₃ nanocrystals, (b) agglomeration and (c) decomposing product of CsPbX₃ nanocrystals, and schematic diagram of (d) phase transition (non-perovskite phase) and (e) phase transition (perovskite phase)

3. (a) Passivation strategy based on hard Lewis acid ligands (left), images under 365 nm UV light (middle), and photoluminescence decay curves (right) of nanocrystals with high and low defect densities^[25]; (b) Schematic diagram of DETAI₃ surface passivation strategy (left), absorption curves (middle) and long-term phase stability (right) of CsPbI₃‧xDETAI₃ thin films^[29]

4. (a) Schematic diagram of Lewis base surface passivation strategy for CsPbX₃ nanocrystals; (b) Theoretical calculation of the binding energy of mono- and dicarboxylic acids on the surface of CsPbI₃ nanocrystals^[34]; (c) Schematic diagram of OPA and OAm-CsPbX₃ surface passivation strategies and photos after multiple purifications^[35]; (d) Surface passivation strategy with zwitterionic ligands (sulfobetaines, phosphocholines and γ-amino acids)^[36]

5. (a) Passivation strategies with different ligands (OAm, OA and DBSA) on the surface of CsPbBr₃ nanocrystals and (b) the corresponding exciton recombination processes^[37]; (c) Schematic diagram of PbBr_x-rich surface of OAm-CsPbBr₃ nanocrystals (left) and Br-rich surface of OAm/OA-CsPbBr₃ nanocrystals (right)^[11]; (d) Photographs showing the resistance of different samples against water treatment of OAm/OA-CsPbBr₃ nanocrystals (above) and OAm-CsPbBr₃ nanocrystals (below)^[11]

6. (a) Schematic diagram of CPB-DBAE@SiO₂ preparation process^[51]; (b) Transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) images of CsPbBr₃@SiO₂ nanocrystals and photographs of water stability^[60]; (c) Schematic representation (left), HRTEM image (middle), and plot of emission intensity under continuous pulsed laser irradiation (right) of CsPbBr₃/CdS nanocrystals^[67]

Table 1. Surface passivation strategies of Lewis acid ligands

Table 2. Surface passivation strategies of Lewis base ligands

Table 3. Characteristics, advantages and disadvantages of different passivation strategies