Organic Sulfonium‐Stabilized High‐Efficiency Cesium or Methylammonium Lead Bromide Perovskite Nanocrystals

Abstract

Herein, we report a new X-type ligand, i.e., organic sulfonium bromide, for high-efficiency CsPbBr 3 and MAPbBr 3 (MA = methylammonium) perovskite nanocrystals (PNCs). We first confirmed the facile synthesis of the titled ligands in N,N-dimethylformamide at room temperature. By reacting dodecylmethylsulfide with allyl bromide, (3-bromopropyl)trimethoxysilane, and 1,4-dibromobutane, respectively, three representative ligands (named DAM, DSM, and DMM) are acquired. All of them result in CsPbBr 3 and MAPbBr 3 PNCs with near-unity photoluminescence quantum yield (PLQY) and decent ambient stability (no less than 90 % PLQY after 2 months) using a room-temperature ligand-assisted reprecipitation technique. Among them, DSM and DMM endow CsPbBr 3 PNCs with higher thermal/light stability arising from the cross-linkable or bidentate ligand structure. Further, DSM-CsPbBr 3 PNCs can be incorporated into polystyrene through in situ thermal polymerization and the composite shows a record-high PLQY of 93.8 %.

Ligand Chemistry of Inorganic Lead Halide Perovskite Nanocrystals

“…Additionally, the 207 Pb spin-echo spectrum (Figure 1d) shows a single peak at 200 nm similar to that reported for bulk MAPbBr 3 (400 ppm) and CsPbBr 3 (250 ppm). 54,55 Surfaceselective 207 Pb NMR spectra obtained through 207 Pb → 1 H CP-HETCOR experiments enabled the detection of the lead atoms proximate to the surface. 56 The similarity in the Pb projection of the surface selective 2D 207 Pb → 1 H CP-HETCOR spectrum and the 207 Pb spin-echo spectrum suggests that most of the lead atoms are present in a bulk environment, which corresponds to the complete PbBr 6 octahedra.…”

“…54,55 Surfaceselective 207 Pb NMR spectra obtained through 207 Pb → 1 H CP-HETCOR experiments enabled the detection of the lead atoms proximate to the surface. 56 The similarity in the Pb projection of the surface selective 2D 207 Pb → 1 H CP-HETCOR spectrum and the 207 Pb spin-echo spectrum suggests that most of the lead atoms are present in a bulk environment, which corresponds to the complete PbBr 6 octahedra. 53 In addition, the 1 H → 133 Cs and the 207 Pb → 1 H 2D NMR correlation experiment spectra indicate the presence of −NH 3 + and α-CH 2 protons of the oleate and alkylammonium surface ligands.…”

Weakening Ligand–Liquid Affinity to Suppress the Desorption of Surface-Passivated Ligands from Perovskite Nanocrystals

“…To retard the migration, a series of ligands such as multidentate, , zwitterionic, , chelating, , phosphonic, − and sulfonic molecules , with stronger binding strength are extensively exploited to improve the colloidal stability via lowering μ solid . As another alternative approach, increasing μ liquid is also feasible in principle to suppress the migration of ligands by weakening ligand–solvent affinity (Scheme ).…”

Halide-Driven Halogen–Hydrogen Bonding versus Chelation in Perovskite Nanocrystals: A Concept of Charge Transfer Bridging

“…The recent reports on using zwitterionic molecules, e.g., lecithin, during the postsynthetic process shows enhanced surface adhesion along with precise size and shape control of perovskite NCs and may open a new direction for enhancing the stability of NCs colloids. − While such zwitterionic molecules are promising for enhancement in the surface coupling, they still form an insulating layer around perovskite NCs and therefore may affect the charge transfer properties. In this regard, it is essential to comprehend the nature of surface coupling of such bidentate ligands on the NCs surface. − Stronger surface coupling of these capping ligands may translate to the inherent lattice vibrations of perovskite NCs and may alter the optical properties of the coupled system. The dependence of size, shape, and composition of such coupling on the perovskite NCs also needs to be understood for tailoring their synthesis as well as their usage in optoelectronics.…”