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

Abstract

High performance CsPbBr 3 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 CsPbBr 3 NCs was modulated by mixing at room temperature with Cs 3 PrCl 6 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.

Surface Ligand Tuning of Coordination Geometry and Pb 6s2 Electronic Pair Stereochemical Activity in MAPbBr3 Perovskite Nanoparticles: A Joint Experimental and Theoretical Insight

“…Figure d shows the Tauc plot obtained from the UV–vis absorption curve, and the band gaps of NPs and MCs are estimated to be 2.58 and 2.29 eV, respectively, indicating a band-gap opening in NPs. These electronic band-edge properties could be contributed to the chemical strain effect of ligands OA and APTES, which agrees with pressure-induced optical and structural changes of perovskite NPs by Cao and Matsuishi et al That is to say, under chemical compression, surface ligands strongly suppressed the grain growth of NPs. With the reduced size in NPs, the perovskite lattice was strained with a jump of the band gap excitonic level to a higher energy.…”

Impact of Molecular Ligands in the Synthesis and Transformation between Metal Halide Perovskite Quantum Dots and Magic Sized Clusters

“…For example, a small amount of different dopants can be added into the A site to change the tolerance factor and electronic properties of the perovskites, while the doping substitution of the B site can reduce the Pb 2+ toxicity, and the X site doping can regulate the band gap of the perovskites. The introduction of dopant elements at specific locations provides an effective solution for improving the stability of the perovskite crystal structure, optimizing luminescence performance, improving nonradiative recombination, and regulating exciton dynamics (Figure a). − Among them, doping different cations at the B site can improve the phase stability, enhance the PL emission intensity, and reduce the toxic Pb content …”

Improvement of Photophysical Properties of CsPbBr3 and Mn2+:CsPb(Br,Cl)3 Perovskite Nanocrystals by Sr2+ Doping for White Light-Emitting Diodes

“…The absence of a systematic shift in the XRD patterns (Figure a) motivated us to investigate the influence of the Sr 2+ -doping concentration on microstrain, which describes local distortions of a crystal lattice. , Microstrain in the studied NCs was calculated from the slope of the WH plot (Figure S4 and Table S3). Figure b shows that microstrain decreases upon Sr 2+ additive until the 2% concentration and then systematically increases at higher concentrations.…”