Revealing the Role of Tin(IV) Halides in the Anisotropic Growth of CsPbX₃ Perovskite Nanoplates

Abstract

CsPbX3 perovskite nanoplates (PNPLs) were formed in a synthesis driven by SnX4 (X=Cl, Br, I) salts. The role played by these hard Lewis acids in directing PNPL formation is addressed. Sn4+ disturbs the acid–base equilibrium of the system, increasing the protonation rate of oleylamine and inducing anisotropic growth of nanocrystals. Sn4+ cations influence the reaction dynamics owing to complexation with oleylamine molecules. By monitoring the photoluminescence excitation and photoluminescence (PL) spectra of the PNPLs grown at different temperatures, the influence of the thickness on their optical properties is mapped. Time‐resolved and spectrally resolved PL for colloidal dispersions with different optical densities reveals that the dependence of the overall PL lifetime on the emission wavelength do not originate from energy transfer between PNPLs but from the contribution of PNPLs with distinct thickness, indicating that thicker PNPLs exhibit longer PL lifetimes.

CsPbI3 Nanocrystals Go with the Flow: From Formation Mechanism to Continuous Nanomanufacturing

“…To preserve a representative population of the different CsPbI 3 NC morphologies synthesized in flow, we used hexane as the antisolvent, which proved to be a better alternative to methyl acetate (washing protocol available in the Note S5, Supporting Information) where all lower PL peaks were preserved post NC washing stage (see Figure S6, Supporting Information). It is worth noting that the antisolvent addition is important to extract the smaller NCs from the crude product mixture, where only centrifugation without any antisolvent addition is not successful in maintaining all CsPbI 3 NC populations of the crude mixture (see Figure S6, Supporting Information), as reported by Bonato et al [31] Figure 5A presents representative TEM images of CsPbI 3 NCs synthesized at four different reaction temperatures and two extreme R p values (2.25 and 9) at the residence time of 4 s. The residence time of 4 s was selected based on the PL and UV-vis absorption spectra shown in Figure 4, where the PL peak reached its equilibrium position (evident from the similar PL peak position between 4 and 16 s). The spectral data (UV-vis absorption, PL, and PLQY) of the CsPbI 3 NC samples presented in Figure 5 along with the TEM images and spectral data of CsPbI 3 NCs synthesized at the residence time of 0.6 s are provided in the Supporting Information (see Figures S7,S8, Table S2, Supporting Information).…”

“…The results shown in Figure 5 reveal a clear morphological difference between CsPbI 3 NCs synthesized at R p of 2.25 versus 9, where the former is dominated by NCubes and the latter by NPLs, that is in agreement with the literature. [20,26,31] In order to better understand the morphological differences of CsPbI 3 NCs obtained at different synthesis conditions, we analyzed the TEM images using the following metrics: NC area, circularity, short side length, and The first contrasting difference is that the circularity for R p of 2.25 has a higher overall relative frequency around 0.785 (perfect square) compared to the more spread-out circularity distribution for CsPbI 3 NCs synthesized with an R p of 9 (Figure 5B). This result is complimented with the trend shown in Figure 5C, where the majority of the CsPbI 3 NCs synthesized at R p of 2.25 has a short edge length of ≈10-12 nm, that is in agreement with the average size of CsPbI 3 NCubes, [1,20] while R p of 9 exhibited a more spread out NPL population with different thicknesses.…”

“…In a different study, Burlakov et al [24] coupled Monte Carlo simulations with experimentation and found that the CsPbBr 3 NPL growth was dictated by the competition between monomer and ligand formation on the NC surface, that is controlled by the temperature and ligand binding energy. The common theme between all proposed hypotheses of LHP NPL formation mechanisms [24,26,28,29,31] is the competition of cesium ions (Cs + ) with oleylammonium ions for the A-site cation in the perovskite NC, where oleylammonium ions impede the growth on the crystalline plane they attach to, leading to the NPL morphology.…”

Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

“…[130] To eliminate some of the complications that arise from changes of OA and OAm ligand interactions as a result of the alteration of ligand ratio or through precursor aging, additives such as metal halide (e.g., ZnBr 2 , FeBr 3 , SnX 4 (X=Cl, Br, I)), alkali metal, or alkaline earth metal salts, or small molecules like thiocyanate, have been incorporated into precursors during synthesis. [90,111,[131][132][133][134][135][136] Some of these additives were shown not only to further stabilize the NCs through inorganic passivation, [111,134] but also to trap the oleate species and promote a pure oleylammonium halide ligand shell. [111] Other studies have focused on altering the concentrations and identities of the alkylamine and alkyl carboxylic acid ligands to understand the effect on NC optical properties, size, morphology, and self-assembly and to target LHP NCs with ideal and controllable properties.…”

ASnX3—Better than Pb‐based Perovskite

“…reconfirms that Sn 4+ disturbs the acid‐base equilibrium of the system (Figure 18), increasing the protonation rate of oleylamine and inducing an anisotropic growth of the nanocrystals due to its complexation with oleylamine molecules. [ 163 ]…”