Strain Modulation for High Brightness Blue Luminescence of Pr³⁺-Doped Perovskite Nanocrystals via Siloxane Passivation

High performance CsPbBr3 nanocrystals (NCs) were synthesized via a hot injection method followed by a room-temperature ligand exchange modification using 3-mercaptopropyltrimethoxysilane (MPTMS). The ligand exchange promotes crystal growth and enhances the photoluminescence quantum yield (PLQY) of the NCs to near unity. The oscillator strength of the interband transition based on UV–vis absorption was surprisingly amplified by a factor of 2.5. The NC’s surface was passivated via S–Pb polar covalent bonding, which shifts the thermodynamic equilibrium and favors NC growth with a higher Br-to-Pb atomic ratio on the surface. Moreover, the perovskite lattice was strained by a cross-linked polymeric network of self-condensed siloxane. The strain within CsPbBr3 NCs was modulated by mixing at room temperature with Cs3PrCl6 NCs for controlled halide exchange and Pr doping; thereby blue emission from the Pr-doped CsPb(Cl/Br)3 NCs was achieved with optimized brightness (PLQY = 88%) at 464 nm.