Controlled Growth of CH₃NH₃PbBr₃ Perovskite Nanocrystals via a Water–Oil Interfacial Synthesis Method

Abstract

Fundamental insights into the reaction kinetics of organic-inorganic lead halide perovskite nanocrystals (LHP NCs) are still limited due to their ultrafast formation rate. Herein, we develop aw ater-oil interfacial synthesis of MAPbBr 3 NCs (MA = CH 3 NH 3 + ), whichp rolongs the reaction time to tens of minutes.T his method makes it possible to monitor in situ the formation process of MAPbBr 3 NCs and observe successive spectral evolutions from 438 to 534 nm in asingle reaction by extending reaction time.T he implementation of this method depends on reducing the formation rate of PbBr 6 4À octahedra and the diffusion rate of MA. The formation of PbBr 6 4À is ar ate-determining step,a nd the biphasic system offers afavorable reaction condition to control the mass transfer of MA. The effects of temperature and concentration of precursor and ligand are investigated in detail.Lead halide perovskite nanocrystals (LHP NCs) have recently inspired significant interest due to their outstanding photophysical characteristics. [1] Much attention has been devoted to the synthesis chemistry [2] and the optoelectronic properties [3] of LHP NCs,p romoting the rapid development of their related applications. [4] However, understanding of the reaction kinetics of LHP NCs has not kept pace.T he biggest obstacle lies in that LHP NCs have an ultrafast formation rate and their nucleation and growth occurs in afew seconds, [5] in contrast with classical NCs (i.e.C dSe,I nP) that exhibit "molecular-like" elementary steps during the process of formation. [6] Thefirst breakthrough happened in all-inorganic LHP NCs. [7] As eries of approaches are employed to reduce the formation rate of monomers (Cs + and PbBr 6 4À )b y involving rate-limiting steps,t hus reducing the overall reaction rate of CsPbBr 3 NCs.F or instance,t he microfluidic platform is employed to lower the reaction rate of CsPbX 3 (X = Br, Cl, and I) NCs by decreasing the feeding rate of precursors. [7a-c] Am icrowave-assisted wet chemical synthesis of CsPbBr 3 NCs is also designed to slow down the reaction and analyze the intermediate products in the formation process. [7d] Recently,the step-by-step growth of CsPbBr 3 NCs is achieved by using nanocluster as monomers and restricting the ligand concentration in the reaction medium. [7e] Notwithstanding significant progresses in slowing down the reaction rate of all-inorganic LHP NCs,t he reaction control of organic-inorganic LHP NCs still remains ac hallenge,e ven using the microfluidic platform. [8] In addition to the difficulty in size control of MAPbX 3 (MA = CH 3 NH 3 + ) NCs with smaller Bohr radius, [9] them ajor cause of failure is related to the existing synthetic methods.A tp resent, MAPbBr 3 NCs are synthesized by the reprecipitation method. [10] Theu sed precursor solution is prepared by dissolving MABr and PbBr 2 together in DMF,w hich has already contained free-standing constituents of PbX 6 4À and MA. Thef ollowing process of mixing the precursor solution with poor solvent is designed just to induce the cr...

Reversible Ultra‐Slow Crystal Growth of Mixed Lead Bismuth Perovskite Nanocrystals: The Presence of Dynamic Capping

“…Recently, Li et al. have reported a slow crystal growth of CH 3 NH 3 PbBr 3 perovskite NC on oil–water interface . Kostopoulou et al.…”

“…[19] However,w hen these two ligandsa re used together,t hey form the oleate anion and olylammonium cation,w hich are better cappinga gentsd ue to the strong interaction with Pb 2 + and X À ,r espectively. [21] Kostopoulou et al very recently reported as low growth of CsPbBr 3 nanowirei nt oluene and as idet os ide coalescence of the nanocrystals is proposed as the mechanism. Akin to most of the nanomaterials, the properties of perovskite NCs dependh ighly on their size and shape.…”

“…have reported as low crystal growth of CH 3 NH 3 PbBr 3 perovskite NC on oil-water interface. [21] Kostopoulou et al very recently reported as low growth of CsPbBr 3 nanowirei nt oluene and as idet os ide coalescence of the nanocrystals is proposed as the mechanism. [22] However,t ot he best of our knowledge,s uch as low crystal growth in normal antisolvent for hybrid perovskite NC has not been observed yet.…”

One-pot synthesis of CsPbBr3 nanocrystals in methyl methacrylate: a kinetic study, in situ polymerization, and backlighting applications

“…35,36 Previous studies revealed the accelerating effect of polar solvents in ionization and an ion exchanging process during the growth of metal salts, while the nucleation rate largely depends on the diffusion of the precursors and monomers in solvents. [37][38][39][40] ODE possesses high viscosity and low polarity that are negative for the separation of the nucleation and growth of the PNCs at low temperature. We infer that the solvents with low viscosity and appropriate polarity will benefit the homogenous growth of PNCs.…”

Toward the Controlled Synthesis of Lead Halide Perovskite Nanocrystals

“…As illustrated in Figure b, by dispersing various ion sources in immiscible two-phase solvents, precursors will slowly diffuse to the interface and initiate reactions. This approach has demonstrated continuous size tuning . Despite its merits, challenges persist in enhancing the stability and optical properties of the resulting NCs due to the use of polar solvents.…”