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

Herein, we report a new X-type ligand, i.e., organic sulfonium bromide, for high-efficiency CsPbBr₃ and MAPbBr₃ (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 CsPbBr₃ and MAPbBr₃ 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 CsPbBr₃ PNCs with higher thermal/light stability arising from the cross-linkable or bidentate ligand structure. Further, DSM-CsPbBr₃ PNCs can be incorporated into polystyrene through in situ thermal polymerization and the composite shows a record-high PLQY of 93.8 %.