Metal halide perovskites nanoparticles, including magic sized clusters (MSCs) and perovskite quantum dots (PQDs), exhibit interesting properties promising for emerging applications in energy and photonics. Their stabilization is critical for maintaining their properties and functionalities. One approach to stabilization is to use molecular ligands to passivate their surface. We have discovered a new class of molecular ligands based on metal coordination compounds, especially trivalent cationic metal complexed with nitrate and hydroxyl ligands, that are highly effective for passivating perovskite MSCs or PQDs. As a matter of fact, one can tune from MSCs to PQDs at will by adjusting the ligand concentration and/or using different ligands, with stronger binding ligands and higher ligand concentration favoring MSCs over PQDs. Both the MSCs and PQDs are highly stable and photoluminescent. Experimental evidence suggest that the planar geometry of the coordination ligands is very important for the outcomes observed. Such ligands should work for both nanoparticles and bulk films, and are likely more desired tan linear or “cone-shaped” ligands. The results indicate that the size, shape, and charge (including distribution) are critical characters affecting the effectiveness of passivation. Furthermore, Due to the nature of multiple defects on the MSC or PQD surface, a combination of ligands is required for effective passivation, essentially demanding a “cocktail” approach. We also found that the approach works well for both all inorganic perovskites such as CsPbBr3 as well as organo-metal halide perovskites such as CH3NH3PbBr3. We suggest that the approach developed may also be useful beyond perovskites.

“Cocktail” approach for effective passivation of metal halide perovskite magic sized clusters and quantum dots involving planar molecular ligands based on metal coordination compounds

2019 Fall National Meeting

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