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Ion-exchange has been widely employed to modify the composition and structure of glasses. In this work, Cs–K ion-exchange was carried out to facilitate the precipitation of cesium lead halide perovskite nanocrystals in the surface layer of glasses. Both Cs 4 PbBr 6 and CsPbBr 3 perovskite nanocrystals and KBr nanocrystals can be precipitated through ion-exchange in nitrate salt. Content of Cs 4 PbBr 6 and CsPbBr 3 perovskite nanocrystals is strongly dependent on the composition of nitrate salt, ion-exchange conditions, and post-thermal annealing. High concentration of Cs in nitrate salt, long ion-exchange duration, and post-thermal annealing are effective to promote the formation of CsPbBr 3 perovskite nanocrystals. Results reported is valuable for the developing of cesium lead halide perovskite nanocrystals embedded glass for light converters. [ABSTRACT FROM AUTHOR]

Colloidal cesium lead halide (CsPbX3) perovskite nanocrystals (PNCs) have been shown to exhibit very bright tunable photoluminescence (PL) in the entire visible range and narrow emission widths with composition control. However, challenges afflict the stability of PNCs, which limits their usage in practical applications. Surface passivation with an additional ligand could be an excellent, easy, and facile approach to enhance the photoluminescence and stability of PNCs. To address the issue of stability, we introduce the abundantly available ascorbic acid as a surface capping ligand to achieve high photoluminescence and stability of CsPbX3 PNCs via post-treatment. Ascorbic acid helps in improving the photoluminescence (PL) quantum yield of all halide variant PNCs, particularly CsPbBr3 and CsPb-(Br/I)3 PNCs. With ascorbic acid post-treatment, the luminescence decay profiles are improved with a significant increase in the PL lifetime. As a proof-of-concept, we recorded PL data of untreated and ascorbic acid-treated PNCs for a considerable amount of time and found that ascorbic acid-capped PNCs exhibit exceptional ambient stability, photostability, and thermal stability. The pure CsPbI3 PNCs, which are thermodynamically unstable at room temperature, become ultrastable in the presence of ascorbic acid, where they showed the preservation of the luminescent phase for 55 d since the date of synthesis when stored in open atmospheric conditions. The ascorbic acid-treated CsPb-(Br/I)3 PNCs also exhibited excellent stability with no trace of halide segregation, unlike the as-synthesized mixed halide perovskites, wherein a blue shift of PL is observed with a significant loss in emission. Stabilizing CsPbX3 PNCs of different halide compositions via a simple surface treatment with ascorbic acid could form the basis for futuristic light-emitting applications. [ABSTRACT FROM AUTHOR]

Colloidal perovskite nanocrystals comprised of all inorganic cesium lead halide (CsPbX3, X = Cl, Br, I or a mixture thereof) have potential as optical gain materials due to their high luminescence efficiency. In this work, cesium lead halide nanocrystals are continuously synthesized via a microreactor system consisting of poly(tetrafluoroethylene) (PTFE) capillaries. The synthesized nanocrystals possess excellent optical properties, including a full width at half maximum of 19–35 nm, high fluorescence quantum yield of 47.8–90.55%, and photoluminescence emission in the range of 450–700 nm. For the same precursor concentrations, the photoluminescence emission peak generally increases with increasing reaction temperature, revealing a controllable temperature effect on the photoluminescence characteristics of the synthesized nanocrystals. For quantum dots synthesized with a Br/I ratio of 1:3, a slight blue shift was observed for reaction temperatures greater than 100 °C. This PTFE-based microreactor system provides the unique capability of continuously synthesizing high-quality perovskite nanocrystals that emit over the full visible spectrum with applications ranging from displays and optoelectronic devices.

Graphical abstract Highlights • We investigate the photoluminescence properties of the Cs 4 PbBr 6 quantum dots. • They have stable intrinsic luminescence spanning from 340 to 378 nm spectral region. • The studies reveal that there is remarkable quantum confinement effect in these QDs. • The large exciton binding energy explains strong room-temperature exciton emission. Abstract Cesium lead halides are novel and superior optoelectronic materials. Unlike the cases of the widely investigated cubic CsPbXr 3 (X = Cl, Br, or I) nanocrystals, people know little about the optical properties of the "zero-dimensional perovskite" Cs 4 PbX 6 nanocrystals. We study the photoluminescence properties of the Cs 4 PbBr 6 quantum dots (QDs) with sizes of only a few nanometers. They exhibit stable wavelength-tunable (from 340 to 378 nm) luminescence stemming from quasi-self-trapped excitons. The spectral characterizations in conjunction with first-principles calculations reveal there is remarkable quantum confinement effect in the Cs 4 PbBr 6 QDs. The large exciton binding energy obtained from both calculation and experiment explains why the trigonal Cs 4 PbX 6 QDs have strong exciton-related absorption and emission at room temperature. This family of wide-gap trigonal cesium lead halide QDs with intrinsic near-UV luminescence have potential applications in short-wavelength photonic nanodevices. [ABSTRACT FROM AUTHOR]

The formation of cesium lead halide perovskite nanocrystals are very effortless due to its extremely fast reaction kinetics. Herein, we present simple hot-inject approach and anion exchange reaction to fabricate all inorganic colloidal CsPbX 3 perovskite nanocrystals (NCs). The colloidal CsPbX 3 NCs with controlling-size exhibit the characteristics of the high luminescent intensity, superior quantum yields (QY, above 69%) and the narrow-band emission tuning, the bandgap energies and emission spectra are readily tunable over the entire visible spectral region of 425–710 nm. Moreover, the third-order nonlinear optical properties of all inorganic colloidal perovskite nanocrystals (CsPbCl 3 , CsPbBr 3 , CsPbI 3 ) were measured using the Z-scan technique, indicating excellent third-order optical nonlinearities. Nonlinear optical susceptibilities reaching to 3.78 × 10 −11 esu for CsPbBr 3 NCs, figure of merit is achieving above 5 for CsPbI 3 NCs. These interesting results demonstrate that the as-prepared all inorganic colloidal CsPbX 3 perovskite nanocrystals are expected to hold great promise for application on nonlinear optoelectronic devices. [ABSTRACT FROM AUTHOR]

We report a novel CsX-stripping mechanism that enables the efficient chemical transformation of nonluminescent Cs4PbX6 (X = Cl, Br, I) nanocrystals (NCs) to highly luminescent CsPbX3 NCs. During the transformation, Cs4PbX6 NCs dispersed in a nonpolar solvent are converted into CsPbX3 NCs by stripping CsX through an interfacial reaction with water in a different phase. This process takes advantage of the high solubility of CsX in water as well as the ionic nature and high ion diffusion property of Cs4PbX6 NCs, and produces monodisperse and air-stable CsPbX3 NCs with controllable halide composition, tunable emission wavelength covering the full visible range, narrow emission width, and high photoluminescent quantum yield (up to 75%). An additional advantage is that this is a clean synthesis as Cs4PbX6 NCs are converted into CsPbX3 NCs in the nonpolar phase while the byproduct of CsX is formed in water that could be easily separated from the organic phase. The as-prepared CsPbX3 NCs show enhanced stability against moisture because of the passivated surface. Our finding not only provides a new pathway for the preparation of highly luminescent CsPbX3 NCs but also adds insights into the chemical transformation behavior and stabilization mechanism of these emerging perovskite nanocrystals. [ABSTRACT FROM AUTHOR]

Recently, all-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals have drawn much attention because of their outstanding photophysical properties and potential applications. In this work, a simple and efficient solvothermal approach to prepare CsPbX3 nanocrystals with tunable and bright photoluminescent (PL) properties, controllable composition, and morphology is presented. CsPbX3 nanocubes are successfully prepared with bright emission high PL quantum yield up to 80% covering the full visible range and narrow emission line widths (from 12 to 36 nm). More importantly, ultrathin CsPbX3 (X = Cl/Br, Br, and Br/I) nanowires (with diameter as small as ≈2.6 nm) can be prepared in a very high morphological yield (almost 100%). A strong quantum confinement effect is observed in the ultrathin nanowires, in which both the absorption and emission peaks shift to shorter wavelength range compared to their bulk bandgap. The reaction parameters, such as temperature and precursors, are varied to investigate the growth process. A white light-emitting device prototype device with wide color gamut covering up to 120% of the National Television System Committee standard has been demonstrated by using CsPbBr3 nanocrystals as the green light source. The method in this study provides a simple and efficient way to prepare high-quality CsPbX3 nanocrystals. [ABSTRACT FROM AUTHOR]

All inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals (PNCs) exhibit promising applications in light-emitting devices due to their excellent photophysical properties. Herein, we developed a low-cost and convenient method for the preparation of CsPbX3 PNCs in a multiligand-assisted reaction system where peanut oil is applied as a ligand source. The mixed-halide PNCs with tunable optical-band gap were prepared by mixing the single-halide perovskite solutions at room temperature. The resulting PNCs had good monodispersity, with dimensions of 8–10 nm, high photoluminescence quantum yield (96.9%), narrow emission widths (15–34 nm), and tunable emission wavelength (408–694 nm), covering the entire visible spectrum. Additionally, various morphologies of PNCs, such as nanospheres, nanocubes, and nanowires, were obtained by controlling reaction temperature and time, and the amount of oleamine with multiple ligands in peanut oil potentially playing a dominant role in the nucleation/growth processes of our PNCs. Finally, the resulting CsPbBr3 PNCs were employed to develop a white light-emitting diode (WLED), demonstrating the potential lighting applications for our method. [ABSTRACT FROM AUTHOR]