Synthesis of Zwitterionic CsPbBr₃ Nanocrystals with Controlled Anisotropy using Surface‐Selective Ligand Pairs

Abstract

Mechanistic studies of the morphology of lead halide perovskite nanocrystals (LHP‐NCs) are hampered by a lack of generalizable suitable synthetic strategies and ligand systems. Here, the synthesis of zwitterionic CsPbBr3 NCs is presented with controlled anisotropy using a proposed “surface‐selective ligand pairs” strategy. Such a strategy provides a platform to systematically study the binding affinity of capping ligand pairs and the resulting LHP morphologies. By using zwitterionic ligands (ZwL) with varying structures, majority ZwL‐capped LHP NCs with controlled morphology are obtained, including anisotropic nanoplatelets and nanorods, for the first time. Combining experiments with density functional theory calculations, factors that govern the ligand binding on the different surface facets of LHP‐NCs are revealed, including the steric bulkiness of the ligand, the number of binding sites, and the charge distance between binding moieties. This study provides guidance for the further exploration of anisotropic LHP‐NCs.

Surface engineering in CsPbX3 quantum dots: from materials to solar cells

“…Other short ligands with stronger interactions with PQDs should be explored. For example, the zwitterionic ligand 92–94 can tightly bound with the PQDs via the chelate effect, while the co-occurrences of cationic and anionic groups can prevent the external neutralization surroundings of PQDs, and thus enhance the structural durability of PQD films. Therefore, zwitterionic ligands should be further explored for application in solar cells.…”

“…Another family of X-type ligands that has received much attention is zwitterionic (or bidentate) ligands, in which the two functional groups with negative and positive charges simultaneously bind to the X-site and A-site, respectively. 61,62,92–94 The long-chain zwitterionic ligands include sulfabetaine, phosphocholine, and γ-amino acid92 (Fig. 8c).…”

“…PbBr 2 and ZnBr 2 are the most effective among several metal bromide salts (PbBr 2 , ZnBr 2 , InBr 3 , CuBr 2 , AgBr) as an excellent bromide donor in enhancing the PLQY of CsPbBr 3 PQDs. 61,89,105–111 The Konstantatos group 94 obtained a near-unity PLQY for CsPbBr 3 QD films post-treated with PbBr 2 . The addition of PbBr 2 which dissolved in both an amine and a carboxylic acid to the as-prepared PQDs induced strong ligand binding at the surface and introduced an excess of Br − .…”

Influence of Binary Ligands in Designing Cesium Lead Halide (CsPbX3, X = Cl, Br, I) Perovskite Nanocrystals-Oleic Acid and Oleylamine

“…This highlights the need for the molecular engineering of zwitterionic ligands. Various kinds of zwitterionic ligands such as aromatic [141], polymeric [150][151][152], photo-crosslinkable [153], amino acids [154], modular zwitterion functionalized polymers [155], carbazole [156], and quaternary ammonium halide-based zwitterionic ligands [157] show an important role in stabilizing highly luminescent Cs LHP NCs are explored. Interestingly, Zhu et al have proposed that both surface-selective and non-selective ligands are necessary to control the morphology and stability of CsPbBr 3 NCs [157].…”

“…Various kinds of zwitterionic ligands such as aromatic [141], polymeric [150][151][152], photo-crosslinkable [153], amino acids [154], modular zwitterion functionalized polymers [155], carbazole [156], and quaternary ammonium halide-based zwitterionic ligands [157] show an important role in stabilizing highly luminescent Cs LHP NCs are explored. Interestingly, Zhu et al have proposed that both surface-selective and non-selective ligands are necessary to control the morphology and stability of CsPbBr 3 NCs [157]. The authors have demonstrated that zwitterionic ligands are surface-selective to achieve anisotropic nanostructures (nanocubes, NPLs and NRs), and didecylamine (DDA)-based surface non-selective ligands could assist for it along with stability.…”