Inducing Isotropic Growth in Multidimensional Cesium Lead Halide Perovskite Nanocrystals

Abstract

A new two‐step synthetic protocol to yield monodisperse spherical zero‐dimensional (0D) Cs4PbX6 nanocrystals (NCs) and three‐dimensional (3D) CsPbX3 NCs is described. The first step of the reaction involves the colloidal synthesis of spherical PbX2 seed NCs, which are subsequently converted to Cs4PbX6 and CsPbX3 NCs through hot injection of a Cs precursor at the desired reaction temperatures. By employing less reactive Pb and halide precursors, the reaction time was extended from several seconds to about five minutes, thereby allowing greater control during the crystallization and growth stages. The adjustment of halide ratios allows color tuning over a wide spectral range (411–669 nm) for CsPbX3 NCs, with high photoluminescence quantum yields (6–65 %) and narrow emission line widths (ca. 13–30 nm). We envisage our spherical NCs to become a starting point for shell growth (e.g., ZnS, CdS, PbS) by overcoming the difficulty of shell growth around thermodynamically unfavorable (i.e., high surface free energy) cuboid‐shaped NCs.

Exciton Relaxation Dynamics in Perovskite Cs4PbBr6 Nanocrystals

“…We have synthesized Cs 4 PbBr 6 NCs via a hot injection method following the reported route (see the details in Section 4 ). 20 In short, lead oxide (PbO) powder was first dissolved in 1-octadecene (ODE) in the presence of oleic acid (OAc) and oleylamine (OAm) at 150 °C in a nitrogen atmosphere. Then, the solution was cooled down to 80 °C and the tetrabutylammonium bromide (TBABr) precursor solution was injected into a PbO mixed solution.…”

“…Cs 2 CO 3 (2.5 mmol, 814 mg) powder was mixed in OAc (2.5 mL) and ODE (40 mL) in a 100 mL three-necked round-bottom glass flask. 20 At first, the solution was dried under vacuum for 1 h at 120 °C. Then, the reaction was heated under a nitrogen atmosphere for another 1 h at 150 °C until all Cs 2 CO 3 reacted with OAc and a transparent solution was obtained.…”

“…TBABr (2 mmol) powder was mixed in OAm (7 mL) and ODE (3 mL) in a 100 mL round-bottom flask. 20 The mixture was kept under vacuum conditions for 1.5 h at 150 °C and then subsequently heated at 200 °C for 1 h under a nitrogen atmosphere. A pale-yellow colored solution was obtained.…”

Oriented Attachment of Perovskite Cesium Lead Bromide Nanocrystals

“…These lower dimensional NCs may offer a great platform for creation of futuristic devices. Recently Mathews group has synthesized spherical shaped CsPbX 3 NCs that can be beneficial for formation of comparatively stable core‐shell nanostructures …”

“…al., and spherical shaped CsPbBr 3 NCs synthesis was followed from the synthesis protocol invented by Mathews et. al . Figure a denotes the absorption (black line) and photoluminescence (PL) spectra (green line) of cubic CsPbBr 3 NCs in hexane solvent.…”