Colloidal Synthesis of Air-Stable CH₃NH₃PbI₃ Quantum Dots by Gaining Chemical Insight into the Solvent Effects

Abstract

Because of the superior optical properties and potential applications in display technology, colloidal synthesis of halide perovskite quantum dots has been intensively studied. Although great successes have been made in the fabrication of green emissive CH 3 NH 3 PbBr 3 quantum dots, the fabrication of stable iodide-based CH 3 NH 3 PbI 3 quantum dots remains a great challenge because of their sensitivity to moisture in the open air. Even in a glovebox, the colloidal CH 3 NH 3 PbI 3 quantum dots obtained from N,N-dimethylformamide suffer from instability caused by fast degradation within days to weeks. In this work, we investigated the interactions between perovskite precursors and various polar solvents as well as their influence on the crystallization of CH 3 NH 3 PbI 3 in reprecipitation synthesis. By gaining chemical insight into the coordination effects, we can explain the degradation of CH 3 NH 3 PbI 3 to the defective crystals with coordinated solvents on the surface and/or intrinsic inner iodine vacancies. On the basis of this understanding, we fabricated air-stable CH 3 NH 3 PbI 3 quantum dots with a tunable size from 6.6 to 13.3 nm by selecting noncoordinated acetonitrile as a good solvent through ligand-assisted precipitation synthesis. The fabrication can be processed under ambient conditions, and the resulting CH 3 NH 3 PbI 3 quantum dots exhibit tunable emission with high photoluminescence quantum yields (maximum of ∼46%) as well as good stability. Moreover, the quantum confinement effects in CH 3 NH 3 PbI 3 quantum dots were discussed by correlating the size-dependent photoluminescence properties with theoretical calculations, which can be described by the infinite quantum well approximation model.

Highly Luminescent Lead Halide Perovskite Quantum Dots in Hierarchical CaF2 Matrices with Enhanced Stability as Phosphors for White Light‐Emitting Diodes

“…Here, a perovskite white LED device was fabricated by mixing the green CaF 2 -CsPbBr 3 with emission peak of 522 nm and red CaF 2 -CsPbBr 1.2 I 1.8 with emission peak of 624 nm on a blue chip. [58] Similarly, even with the presence of the protecting CaF 2 shielding, the luminescence of red PQDs still quenched within a few days in the ambient air (results not shown here). Figure 4b shows the CIE chromaticity coordinates of three primary colors for the blue chip, green nanocomposites, red PQDs, and the optimized WLED at (0.158, 0.018), (0.116, 0.772), (0.666, 0.333), and (0.358, 0.276).…”

Unconventional solution-phase epitaxial growth of organic-inorganic hybrid perovskite nanocrystals on metal sulfide nanosheets

“…Based on previous reports, colloidal organic-inorganic hybrid perovskite NCs are usually prepared through ligand-assisted reprecipitation (LARP) methods [38,39], which began with the dissolution of lead halide and alkylammonium halide in a polar solvent like DMF together with surfactants such as OA and OLA. This precursor solution was then injected into a nonpolar solvent (e.g., toluene or hexane) under stirring, during which perovskite NCs were precipitated due to the decrease of solubility.…”

“…However, such heterojunctions have been realized mostly via solid-state methods typically involving chemical vapor deposition (CVD), [35] mechanical exfoliation [36] and/or dry transfer [33], which are difficult to scale-up for practical applications. Direct growth of perovskite crystals on dispersible 2D materials in solution is expected to enable the scalable production of solution-processible heterostructures, but has not been realized, because a non-polar solvent is usually needed for the precipitation of perovskite crystals [38,39] which is incompatible with most solvation conditions for 2D materials.…”

Lead Halide Perovskite Nanocrystals in the Research Spotlight: Stability and Defect Tolerance

“…44 Soon after that first publication, Zhong’s group introduced a ligand-assisted reprecipitation (LARP) technique (as shown in Figure 2a) in a mixture of a good and a poor solvent to produce MAPbX 3 (X = Cl, Br, I) NCs with a tunable bandgap by varying halide elements; the same group also reported improved LARP and in situ fabrication later. 39,45−47 Later in Huang’s related report, 40 bandgap tunability of MAPbBr 3 NCs while controlling the LARP process by modifying the poor solvent’s temperature was demonstrated (Figure 2b), and NCs with high PL QYs of up to 93% and high crystallinity (Figure 2c) were obtained. 1D and 2D perovskite NCs have also been explored, and quantum confinement has been completely verified and quantified in the 2D case.…”