Acid–Amine Equilibria for Formation and Long-Range Self-Organization of Ultrathin CsPbBr₃ Perovskite Platelets

Abstract

Impact of acid–amine equilibrium for triggering the formation of CsPbBr3 platelets and subsequent long-range self-assembly as a function of acid concentration is reported. The study was performed by treating Cs precursor followed by oleic acid to the ongoing process of L2PbBr4 layered perovskites formation at room temperature, and this led to the thinnest possible platelets of CsPbBr3 with one atomic layer of Cs insertion. These platelets form self-assembly in the micrometer range, and this ordering was tuned as a function of oleic acid concentration and reaction time. With evidence obtained from in situ live monitoring by optical microscopy of these assemblies during the ongoing reaction in solution and analyzing the collected samples ex situ by electron microscopy, it was established that these long-range 1D organizations of platelets took place in solution. Details of the insights of the formation, self-assembly, and impact of different reaction parameters in the formation of these platelets are investigated and reported in this Letter.

Seed‐Mediated Synthesis of Colloidal 2D Halide Perovskite Nanoplatelets

“…In addition, the growth of Cs‐based LHP NPL can be accelerated by heating. Similarly, in a previous study, slow reaction kinetics in CsPbBr 3 NPLs were observed by Mehetor et al [35] . The narrowest emission linewidth was observed in L 2 [FAPbX 3 ]PbX 4 NPLs as shown in Figure 4c.…”

“…Additionally, powder XRD patterns of L 2 [APbX 3 ]PbX 4 samples were shown in Figure S3. Periodic peaks in the XRD pattern indicate 4.3 nm stacking distance between NPL superstructure [18,35,44] . The STEM images in Figure 2f and g reveal that the nanoparticles are of platelet morphology.…”

“…combined PbBr 2 , oleic acid, and oleylamine at elevated temperatures, and then cooled the reaction mixture down to room temperature. Subsequently, the prepared reaction mixture was reacted with Cs‐oleate at room temperature and nanoplatelets were generated [35–36] . In another study, Udayabhaskararao et al.…”

Unusual Temperature Dependence of Bandgap in 2D Inorganic Lead‐Halide Perovskite Nanoplatelets

“…Note that the interplanar spacing equals the NPLs thickness plus the two times length of the oleic acid ligand (≈1.5 nm) on each side of the single NPL, and the NPLs thickness can be approximated as n × 0.6 nm, where n represents the layer number of 2D arrangement of corner‐sharing [PbBr 6 ] 4− octahedra with a thickness of ≈0.6 nm. [ 13 ] Therefore, the measured stacking distance of ≈4.1 nm manifests an average NPL thickness of ≈1.1 nm, corresponding to approximately two monolayers of [PbBr 6 ] 4− octahedra. Consistently, the TEM images showing stacked CsPbBr 3 NPLs standing on their edges give an estimated thickness of a single NPL as ≈1.4 nm (Figure S1, Supporting Information).…”

Colloidal synthesis of lead-free all-inorganic Cs3Sb2BrxI9-x nanocrystals

“…Specifically, OnA can form a chelate with Sb 3+ metal ions whereas OAm can stabilize the resulting NC and NW formation. The morphology of Cs 3 Sb 2 Br 9 NCs in terms of NCs and NWs can be tuned by varying the proportion of ligands and the selective precipitation [19]. FTIR spectroscopy showed the presence of OAm, OnA, and OA on the surfaces of the Cs 3 Sb 2 Br 9 NCs (Figure 1c).…”