Optical Properties of Colloidal CH₃NH₃PbBr₃ Nanocrystals by Controlled Growth of Lateral Dimension

Abstract

Organometal halide perovskites become important in the photovoltaic and light emitting devices due to the compositional flexibility with AMX 3 formula (A is a monovalent organic ammonium cation; M is a metal ion; X is a halogen atom), imposing a significant demand to develop a synthetic route toward new types of nanocrystals. Although chemical pathways for perovskites nanoparticles were developed on the basis of the reprecipitation method, poor control of the nucleation and growth process results in a large size polydispersity that induces the ambiguities associated with a quantum confinement effect depending on their size. Here, a modified reprecipitation method is presented for the synthesis of CH 3 NH 3 PbBr 3 perovskite nanoparticles with a controlled nanoparticle size by systematically tuning the feed ratio of the precursors. Fine control of the nanocrystal size provides new insights into the quantum confinement effect observed in microscale and nanoscale perovskite materials, where their energy bandgap is associated with the thickness of nanoparticles and invariant to preferential growth in a lateral dimension.

Ligand Assisted Control of Photoluminescence in Organometal Perovskite Nanocrystals

“…As a result, smaller nanocrystals emit shorter wavelength photoluminescence. According to the dependence of the energy of exciton transitions in MAPBr nanocrystals on the nanocrystal diameter known from the literature [16] the synthesized nanocrystals have a size less than 20 nm:…”

Solubility‐Controlled Room‐Temperature Synthesis of Cesium Lead Halide Perovskite Nanocrystals

“…In addition, their chemical and thermal stability, [4][5][6] owing to the replacement of weaklybonded organic components such as methylammonium (MA + ) and formamidinium (FA + ) with the inorganic cation (Cs + ) in their crystal structure, are favorable for practical application compared to those of organic-inorganic hybrid lead halide perovskites. [7][8][9][10] For the synthesis of IHP NCs, the hot-injection method has been commonly utilized by adopting the presynthesized cesium oleate (CsOL) soluble in organic solvent (i. e., octadecene) at high temperature (above 120°C) due to the limited solubility of inorganic Cs precursors. [6,11,12] Although great success to control their chemical composition, size, and morphology have been achieved in hot-injection method, more practical approach for scalable synthesis with a higher reaction or production yield still remains a challenge due to an inhomogeneous nucleation arising from a drop in the temperature by the injection of large quantities of the precursor solution.…”

“…[16,17] Alternative routes to overcome these limitations were reported such as the solvothermal, [18] ultrasonication, [19] and ligand-assisted reprecipitation (LARP) method. [20,21] In particular, the LARP technique has been widely used to synthesize the organic-inorganic hybrid lead halide perovskites NCs, [9,10,17,22] which does not require heating and inert atmosphere. [20,21] The recrystallization of the precursors (dissolved in a good solvent) can be induced by their supersaturation in a poor solvent (e. g. toluene), resulting in the formation of colloidal NCs in the presence of ligands (mainly carboxylic acids and primary amines).…”

“…Inorganic lead halide perovskite (IHP) quantum dots with the general formula of CsPbX 3 (X=Cl, Br, I) have attracted great attention as promising candidates for high‐performance light‐emitting diodes (LEDs), [1–3] owing to their high photoluminescence quantum yield (PL QY), narrow PL emission bandwidths, and tunable bandgap energy. In addition, their chemical and thermal stability, [4–6] owing to the replacement of weakly‐bonded organic components such as methylammonium (MA + ) and formamidinium (FA + ) with the inorganic cation (Cs + ) in their crystal structure, are favorable for practical application compared to those of organic‐inorganic hybrid lead halide perovskites [7–10] . For the synthesis of IHP NCs, the hot‐injection method has been commonly utilized by adopting the pre‐synthesized cesium oleate (CsOL) soluble in organic solvent (i. e., octadecene) at high temperature (above 120 °C) due to the limited solubility of inorganic Cs precursors [6,11,12] .…”

A Paper‐Based Platform for Long‐Term Deposition of Nanoparticles with Exceptional Redispersibility, Stability, and Functionality

“…Colloidal nanoparticles (NPs) have been widely investigated for the last several decades because of their unique quantum‐confinement‐effect‐driven optical, electronic, magnetic, and chemical properties . Coupled with their nanometer‐scale size, extremely high surface area to volume ratio, and high reactivity, NPs are actively used for diverse applications in biological, environmental, analytical, medicinal, and energy‐related fields …”