Ligand Dependent Growth and Optical Properties of Hybrid Organo-metal Halide Perovskite Magic Sized Clusters

Abstract

Magic sized clusters (MSCs), small nanoparticles with a single size or narrow size distribution, possess unique chemical and physical properties. CH3NH3PbBr3 perovskite MSCs (PMSCs) were synthesized using butylamine (BTYA) and valeric acid (VA) as well as 3,3-diphenylpropylamine (DPPA) and VA as capping ligands in an excess amount. The PMSCs were characterized using UV–vis and photoluminescence (PL) spectroscopy. For BTYA-VA PMSCs, there is an excitonic absorption peak at 424 nm and PL peak at 434 nm, while the DPPA-VA PMSCs exhibit an absorption peak at 428 nm and PL peak at 451 nm. The size and optical properties of the PMSCs are found to be dependent on the ligands used for passivation. Additionally, in a series dilution of DPPA-VA PMSCs in toluene, it was discovered that different sized perovskite quantum dots (PQDs) can be synthesized with tunable PL emission with peaks ranging between 451 and 525 nm. This phenomenon was not observed for BTYA-VA PMSCs. This contrast indicates the unique interaction between the DPPA ligand and the toluene solvent for the dilution-induced PQD formation. These findings provide new insights into the mechanism of growth and stability of PMSCs that are useful for generating and understanding the formation of larger nanostructures such as QDs.

Interplay between Perovskite Magic-Sized Clusters and Amino Lead Halide Molecular Clusters

“…Detail of the MAPbBr 3 -VA-BTYA PMSC synthesis is described in the supporting information (SI). The UV-vis absorption and PL spectra of MAPbBr 3 -VA-BTYA PMSC solution are shown in Figure 1(a) , with the major absorption peak at 424 nm and PL peak at 434 nm, as we reported previously [ 20 ]. Interestingly, these optical peaks decrease in intensity, and simultaneously, a new absorption peak at 402 nm and PL peak at 410 nm appear with intensity increasing over time.…”

“…MAPbBr 3 PMSCs with BTYA and VA passivating ligands were synthesized using the reprecipitation method, as described in our previous report [ 20 ]. Detail of the MAPbBr 3 -VA-BTYA PMSC synthesis is described in the supporting information (SI).…”

Synergetic effect of the surface ligand and SiO2 driven photoluminescence stabilization of the CH3NH3PbBr3 perovskite magic-sized clusters

“…The metastability behaviour of PMSCs owing to the abundant charging defects in perovskite surface, including positive-charge defect (i.e., halide ion vacancy) and negative-charge defects (i.e., cation vacancy and PbX 4 2− anti-site defects) 8 . The surface passivation MSCs by various capping ligands, including organic acid and amines have been reported 9 , 10 . It was demonstrated that the PMSCs and PQD structure could be tunning by adjusting the ligand concentration ratio between acid and amines-based ligands implying the crucial role of the ligands to the MSCs formation 9 , 10 .…”

“…The surface passivation MSCs by various capping ligands, including organic acid and amines have been reported 9 , 10 . It was demonstrated that the PMSCs and PQD structure could be tunning by adjusting the ligand concentration ratio between acid and amines-based ligands implying the crucial role of the ligands to the MSCs formation 9 , 10 . Unfortunately, the dynamic nature of the interaction between PMSCs surface and capping ligands permits the ligand detachment from the PMSCs surface under various conditions 11 .…”

“…Unfortunately, the dynamic nature of the interaction between PMSCs surface and capping ligands permits the ligand detachment from the PMSCs surface under various conditions 11 . A sample preparation 9 , including vacuum conditioning 10 , 12 , drying process 13 , or even simple purification steps that alter the samples' ligand concentrations 14 , may disrupt the initial PMCS structure concerning the reliability characterization. The ligand's highly dynamic binding state that strongly correlated to their concentration might result in various complex problems in those sample preparation.…”