15243-48-8

Basic information

• Product Name: 2,6-Difluoro-3-hydroxybenzaldehyde
• Synonyms: Benzaldehyde, 2,6-difluoro-3-hydroxy- (9CI);2,4-Difluoro-3-formylphenol
• CAS NO: 15243-48-8
• Molecular Weight: 158.1022664
• Mol File: 15243-48-8.mol
• Article Data: 133

Chemical Properties

• CAS DataBase Reference: 2,6-Difluoro-3-hydroxybenzaldehyde(CAS DataBase Reference)
• NIST Chemistry Reference: 2,6-Difluoro-3-hydroxybenzaldehyde(15243-48-8)
• EPA Substance Registry System: 2,6-Difluoro-3-hydroxybenzaldehyde(15243-48-8)

Safety Data

• Hazardous Substances Data: 15243-48-8(Hazardous Substances Data)

Usage

General Description

2,6-Difluoro-3-hydroxybenzaldehyde is a chemical compound with the molecular formula C7H4F2O2. It is a derivative of benzaldehyde, with two fluorine atoms attached to the 2 and 6 positions, and a hydroxyl group attached to the 3 position. 2,6-Difluoro-3-hydroxybenzaldehyde is commonly used in organic synthesis and pharmaceutical research as a building block for synthesizing various pharmaceuticals and agrochemicals. It possesses important biological activities, including anti-cancer, anti-inflammatory, and anti-microbial properties, making it a valuable compound in drug development. Additionally, it is also used as a starting material in the preparation of various other organic compounds.

Upstream product

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Downstream Products

• 18041-25-3 CsPbI₃ 
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• 7787-69-1 caesium bromide 

Relevant articles and documents

α-Halo Ketone for Polyhedral Perovskite Nanocrystals: Evolutions, Shape Conversions, Ligand Chemistry, and Self-Assembly

Bright lead halide perovskite nanocrystals, which have been extensively studied in the past 5 years, are mostly confined to a six faceted hexahedron (cube/platelet) shape. With variations of ligand, precursor, reaction temperature, and surface modification, their brightness has been enhanced and phase became stable, but ultimate nanocrystals still retained the hexahedron cube or platelet shape in most of the hot injection reactions. In contrast, by exploration of α-halo ketone in amine as a halide precursor, different shaped nanocrystals without compromising the photoluminescence quantum yield (PLQY) are reported. Confining to orthorhombic CsPbBr3, the obtained nanocrystals are stabilized by 12 facets ({200}, {020}, {112}) and led to 12 faceted rhombic dodecahedrons. These facets are absolutely different from six ({110}, {002}) equivalent facets of widely reported orthorhombic cube shaped CsPbBr3 nanocrystals. These also retained the colloidal and phase stability, as well as showed near unity PLQY. With further annealing, these are transformed to 26 faceted rhombicuboctahedrons by dissolving all their vertices. Importantly, these 12 faceted nanocrystals showed wide area self-assembly in most of the reactions. It has also been concluded that primary ammonium ions led to six faceted nanocrystals, but tertiary ammonium ions obtained in this case stabilized different group of facets. While perovskite nanocrystals were broadly confined to only nanocubes, these new nanocrystals with intense emission would certainly provide a new avenue for continuing their further research.

Highly Photoluminescent CsPbBr3/CsPb2Br5NCs@TEOS Nanocomposite in Light-Emitting Diodes

All-inorganic halide perovskite (CsPb2Br5) nanocrystals (NCs) have received widespread attention owing to their unique photoelectric properties. This work reports a novel strategy to control the phase transition from CsPbBr3 to CsPb2Br5 and investigates the effects of different treatment times and treatment temperatures on perovskite NCs formation. By controlling the volume of tetraethoxysilane (TEOS) added, the formation of different phases of perovskite powder can be well controlled. In addition, a white light-emitting diode (WLED) device is designed by coupling the CsPbBr3/CsPbBr3-CsPb2Br5 NCs@TEOS nanocomposite and CaAlSiN3:Eu2+ commercial phosphor with a 460 nm InGaN blue chip, exhibiting a high luminous efficiency of 57.65 lm/W, color rendering index (CRI) of 91, and a low CCT of 5334 K. The CIE chromaticity coordinates are (0.3363, 0.3419). This work provides a new strategy for the synthesis of CsPbBr3/CsPbBr3-CsPb2Br5 NCs@TEOS nanocomposite, which can be applied to the field of WLEDs and display devices.

Templated-Assembly of CsPbBr3 Perovskite Nanocrystals into 2D Photonic Supercrystals with Amplified Spontaneous Emission

Perovskite nanocrystals (NCs) have revolutionized optoelectronic devices because of their versatile optical properties. However, controlling and extending these functionalities often requires a light-management strategy involving additional processing steps. Herein, we introduce a simple approach to shape perovskite nanocrystals (NC) into photonic architectures that provide light management by directly shaping the active material. Pre-patterned polydimethylsiloxane (PDMS) templates are used for the template-induced self-assembly of 10 nm CsPbBr3 perovskite NC colloids into large area (1 cm2) 2D photonic crystals with tunable lattice spacing, ranging from 400 nm up to several microns. The photonic crystal arrangement facilitates efficient light coupling to the nanocrystal layer, thereby increasing the electric field intensity within the perovskite film. As a result, CsPbBr3 2D photonic crystals show amplified spontaneous emission (ASE) under lower optical excitation fluences in the near-IR, in contrast to equivalent flat NC films prepared using the same colloidal ink. This improvement is attributed to the enhanced multi-photon absorption caused by light trapping in the photonic crystal.

Time-dependent transformation routes of perovskites CsPbBr3and CsPbCl3under high pressure

All-inorganic halide perovskites are prospective materials for diverse applications in photovoltaic and optoelectronic devices. Their high performance is associated with good operational stability, which is the key problem of hybrid organic-inorganic perovskites. However, for these materials only fragmentary information is available on the mechanical robustness and response to external stress, fundamentally important for strain engineering in multilayers, pressure-assisted technologies, and flexible panels applications. Here we show that all-inorganic perovskites CsPbX3 (where X = Cl, Br) undergo various types of pressure-induced transformations, including reversible phase transitions, irreversible chemical reactions reducing the dimensionality of PbX6 frameworks, and amorphization. The transformation routes depend on the mode of the applied stress and are related to the kinetics of transitions to the most stable phases. The slow-kinetics transformations in a moderate pressure range of technological importance, between 0.5 and 1.5 GPa, can require days or even weeks, depending on the sample quality and external stimuli. The pressure-induced narrowing and widening of energy gaps has been explained by the mechanism combining Pb-X bond lengths and PbX6 octahedra tilts with the electronic structure of the crystals.

CsPbBr3nanowire polarized light-emitting diodes through mechanical rubbing

Anisotropic films composed of aligned CsPbBr3nanowires (NWs) have been successfully fabricated using a mechanical rubbing method. The films with a dense and uniform morphology show polarization photoluminescence (PL) behavior. Combined with an optimal device structure, a polarized light-emitting diode (LED) with a turn-on voltage as low as 6.5 V was obtained.

Universal Oxide Shell Growth Enables in Situ Structural Studies of Perovskite Nanocrystals during the Anion Exchange Reaction

The ability to tune thin oxide coatings by wetchemistry is desirable for many applications, yet it remains a key synthetic challenge. In this work, we introduce a general colloidal atomic layer deposition (c-ALD) synthesis to grow an alumina shell with tunable thickness around nanocrystalline cores of various compositions spanning from ionic semiconductors (i.e., CsPbX3, with X = Br, I, Cl) to metal oxides and metals (i.e., CeO2 and Ag). The distinctive characteristics of each core (i.e., emission, facile surface functionalization, stability) allowed us to optimize and to elucidate the chemistry of the c-ALD process. Compared to gas-phase ALD, this newly developed synthesis has the advantage of preserving the colloidal stability of the nanocrystalline core while controlling the shell thickness from 1 to 6 nm. As one example of the opportunities offered by the growth of a thin oxide shell, we study the anion exchange reaction in the CsPbX3 perovskites nanocrystals by in situ X-ray diffraction, which had been impeded so far by the instability of this class of materials and by the fast exchange kinetics.

Zinc ions doped cesium lead bromide perovskite nanocrystals with enhanced efficiency and stability for white light-emitting diodes

All-inorganic cesium lead halide perovskite nanocrystals (NCs) are considered as an excellent candidate material for light-emitting devices (LED) displays because of their great photo-physical properties. However, the efficiency and stability of these materials are still unsatisfactory, which is the main disadvantage hindering the commercialization of the perovskite NCs based LED displays. On the other hand, the poisonous element lead (Pb) restricted the large-scale application of the perovskite NCs. Here we reported a hot-injection method by doping zinc ions into the CsPbBr3 NCs with enhanced photoluminescence (PL) properties and stability in ambient air. The doped NCs exhibit the highest photoluminescence quantum yield (PLQY) of 91.3% and a narrow full width at half-maximum (FWHM) of 15.5 nm. The improved the optical properties and stability of the doped NCs may result from the enhanced formation energies of perovskite lattices and the surface passivation. Finally, a white light-emitting diode (WLED) was fabricated by combining the green-emitting CsPbBr3:Zn2+ doped NCs and red-emitting K2SiF6:Mn6+ phosphors along with a blue LED chip, which exhibits a luminous efficiency of 36 lm/W, a chromaticity coordinate of (0.327, 0.336), a color temperature (CCT) of 5760 K and a wide color gamut (137% of the National Television System Committee).

Efficient white LEDs with bright green-emitting CsPbBr3 perovskite nanocrystal in mesoporous silica nanoparticles

Metal-halide perovskites have been hailed as remarkable materials for photovoltaic devices and, recently, their star has also been on the rise in optoelectronics and photonics. Nevertheless, challenging issues, such as the thermal/chemical stability and high-performance devices with long-term stability, limit their practical applications. Here, we successfully prepared CsPbBr3 NCs incorporated into mesoporous silica (NCs-MS) by a simple stirred of MS with CsPbBr3 NCs blended in toluene solution. The resultant NCs-MS nanocomposite exhibit excellent optical performance and good thermal and photostability under illumination of UV light for 120 h. Additionally, NCs-MS nanocomposite is resistant to water, which are beneficial for the fabrication of white light-emitting diode (WLED) devices. Thereby a WLED was constructed by combining NCs-MS nanocomposite with Sr2Si5N8:Eu2+ red phosphor on an InGaN blue chip, achieving a highly efficient luminous efficacy of 47.6 lm/W. Moreover, the WLED also demonstrate wonderful color stability under 120 mA current. This work opens up the exciting opportunity of using all-inorganic CsPbBr3 NCs-MS nanocomposite for high performance and low-cost WLEDs applications.

Metal Halide Perovskite Supercrystals: Gold-Bromide Complex Triggered Assembly of CsPbBr3 Nanocubes

Using nanocrystals as "artificial atoms" to construct supercrystals is an interesting process to explore the stacking style of nanoscale building blocks and corresponding collective properties. Various types of semiconducting supercrystals have been constructed via the assembly of nanocrystals driven by the entropic, electrostatic, or van der Waals interactions. We report a new type of metal halide perovskite supercrystals via the gold-bromide complex triggered assembly of newly emerged attractive CsPbBr3 nanocubes. Through introducing gold-bromide (Au-Br) complexes into CsPbBr3 nanocubes suspension, the self-assembly process of CsPbBr3 nanocubes to form supercrystals was investigated with the different amount of Au-Br complexes added to the suspensions, which indicates that the driven force of the formation of CsPbBr3 supercrystals included the van der Waals interactions among carbon chains and electrostatic interactions between Au-Br complexes and surfactants. Accordingly, the optical properties change with the assembly of CsPbBr3 nanocubes and the variation of mesoscale structures of supercrystals with heating treatment was revealed as well, demonstrating the ionic characteristics of CsPbBr3 nanocrystals. The fabricated CsPbBr3 supercrystal presents a novel type of semiconducting supercrystals that will open an avenue for the assembly of ionic nanocrystals.

Mechanochemical synthesis of a processable halide perovskite quantum dot-MOF composite by post-synthetic metalation

Perovskite quantum dots (PQDs) are some of the most sought after materials for optoelectronic and photovoltaic applications. We report the mechanochemical, solvent-free synthesis of a PQD?MOF composite using a post-synthetically PbII metalated

Engineering Sensitized Photon Upconversion Efficiency via Nanocrystal Wavefunction and Molecular Geometry

Triplet energy transfer from inorganic nanocrystals to molecular acceptors has attracted strong attention for high-efficiency photon upconversion. Here we study this problem using CsPbBr3 and CdSe nanocrystals as triplet donors and carboxylated anthracene isomers as acceptors. We find that the position of the carboxyl anchoring group on the molecule dictates the donor-acceptor coupling to be either through-bond or through-space, while the relative strength of the two coupling pathways is controlled by the wavefunction leakage of nanocrystals that can be quantitatively tuned by nanocrystal sizes or shell thicknesses. By simultaneously engineering molecular geometry and nanocrystal wavefunction, energy transfer and photon upconversion efficiencies of a nanocrystal/molecule system can be improved by orders of magnitude.

Highly Luminescent Copper Iodide Cluster Based Inks with Photoluminescence Quantum Efficiency Exceeding 98%

Highly luminescent inks are desirable for various applications such as decorative coating, art painting, and anticounterfeiting, to name a few. However, present inks display low photoluminescent efficiency requiring a strong excitation light to make them glow. Here, we report a highly luminescent ink based on the copper-iodide/1-Propyl-1,4-diazabicyclo[2.2.2]octan-1-ium (Cu4I6(pr-ted)2) hybrid cluster with a quantum efficiency exceeding 98%. Under the interaction between the Cu4I6(pr-ted)2 hybrid cluster and polyvinylpyrrolidone (PVP), the highly luminescent Cu4I6(pr-ted)2/PVP ink can be facilely prepared via the one-pot solution synthesis. The obtained ink exhibits strong green light emission that originates from the efficient phosphorescence of Cu4I6(pr-ted)2 nanocrystals. Attractively, the ink displays high conversion efficiency for the ultraviolet light to bright green light emission due to its wide Stokes shift, implying great potential for anticounterfeiting and luminescent solar concentrator coating.

High-quality CsPbBr3 perovskite nanocrystals for quantum dot light-emitting diodes

Metal halide perovskites, such as CsPbX3 (X = Cl, Br, and I), have gained extensive attention due to their increasing demand in optoelectronic applications such as solar cells and lighting-emitting devices. Herein, we report a versatile approach to synthesize high-quality CsPbBr3 perovskite nanocrystals (sized 5-15 nm) by ligand-assisted reprecipitation at room temperature. The monodispersed CsPbBr3 nanocube perovskites displayed relatively high photoluminescence quantum yields of 50-80%. By virtue of the quantum size effects, the bandgap energies were manipulated from blue to green spectral regions (410-530 nm). In addition, through compositional modulations of the anion exchange technique, the bright photoluminescence could be almost tuned over the entire visible spectral region (450-650 nm). Furthermore, the photoluminescence of the CsPbBr3 nanocrystals was characterized by narrow emission line widths of 15-50 nm and radiative lifetimes of 5-15 ns. Finally, by taking advantage of these outstanding merits, the CsPbBr3 perovskites were successfully utilized in the application of highly fluorescent patterning and color-purity light-emitting diodes.

Stable and Efficient Blue-Emitting CsPbBr3 Nanoplatelets with Potassium Bromide Surface Passivation

Colloidal all-inorganic perovskites nanocrystals (NCs) have emerged as a promising material for display and lighting due to their excellent optical properties. However, blue emissive NCs usually suffer from low photoluminescence quantum yields (PLQYs) and poor stability, rendering them the bottleneck for full-color all-perovskite optoelectronic applications. Herein, a facile approach is reported to enhance the emission efficiency and stability of blue emissive perovskite nano-structures via surface passivation with potassium bromide. By adding potassium oleate and excess PbBr2 to the perovskite precursor solutions, potassium bromide-passivated (KBr-passivated) blue-emitting (≈450 nm) CsPbBr3 nanoplatelets (NPLs) is successfully synthesized with a respectably high PLQY of 87%. In sharp contrast to most reported perovskite NPLs, no shifting in emission wavelength is observed in these passivated NPLs even after prolonged exposures to intense irradiations and elevated temperature, clearly revealing their excellent photo- and thermal-stabilities. The enhancements are attributed to the formation of K-Br bonding on the surface which suppresses ion migration and formation of Br-vacancies, thus improving both the PL emission and stability of CsPbBr3 NPLs. Furthermore, all-perovskite white light-emitting diodes (WLEDs) are successfully constructed, suggesting that the proposed KBr-passivated strategy can promote the development of the perovskite family for a wider range of optoelectronic applications.

Stable Blue Luminescent CsPbBr3 Perovskite Nanocrystals Confined in Mesoporous Thin Films

Creating CsPbBr3 perovskite nanocrystals with bright blue emission is challenging because their optical properties depend sensitively on structure. Growing perovskites in mesoporous templates bypasses some of these purification issues because the size of the nanocrystal is governed by the dimensions of the pores. Mesoporous silica consisting of aligned channels with tunable diameter can be easily synthesized and used as a template. When the perovskite solution evaporates and retreats, some of the liquid remains trapped in the interconnecting pores by discontinuous dewetting. The precursor crystallizes, generating stable ca. 3.1 nm blue-emitting perovskite nanocrystals. The mesoporous template also serves as a protective barrier to preserve the optical properties of the CsPbBr3 from atmospheric conditions. Compared to the bulk crystals and the powder composite, the strong blue-shift of the emission peak in the film is accompanied by a decrease in the longer lifetime component and an 8-fold increase in the external quantum efficiency.

Microwave-Enhanced Chemistry at Solid-Liquid Interfaces: Synthesis of All-Inorganic CsPbX3 Nanocrystals and Unveiling the Anion-Induced Evolution of Structural and Optical Properties

We demonstrate how microwaves could enhance the chemistry at interfaces of heterogeneous reactions involved in the microwave-solvothermal (MW-ST) synthesis of all-inorganic CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (PNCs) within 6 min, unlike a conventional hot-injection method that requires 3 h. The enhanced MW-ST reaction rate was quantitatively analyzed by the Eyring equation, and it has been observed that the decreased activation free energy (ΔG?) and increased activation entropy (ΔS?) are caused by changes in the relative energies of reactants at their solid-liquid interfaces, leading to the formation of hot spots , where microwave energy absorption is at its maximum. This rapid and homogeneous microwave heating could facilitate the self-assembly of uniformly distributed CsPbX3 nanocubes with precise control over the stoichiometric ratio, as confirmed by high-resolution transmission electron microscopy and energy-dispersive X-ray analyses. X-ray diffraction and Raman results indicate that lattice contraction and expansion in CsPbBr3-yXy have occurred because of an increase in the metal-halide bond length upon moving down the groups Cl → Br → I, as further ascertained by the Rietveld refinement studies. These anion-induced structural variations accordingly affected the electronic properties of MW-ST-synthesized CsPbX3 PNCs, which is apparent from the shifts in their conduction-band (CB) and valence-band (VB) positions. Consequently, the optical properties were also altered, resulting in a color-tuned emission from blue to red, with excellent photoluminescence quantum yields (up to 92%) and narrow emission line widths, as is evident from UV-vis and photoluminescence spectroscopy. The MW-ST-synthesized CsPbX3 PNCs were used as color-conversion layers for the fabrication of light-emitting diodes (LEDs) with commercial 456 nm UV-LED chips.

Triplet Energy Transfer from Perovskite Nanocrystals Mediated by Electron Transfer

Triplet energy transfer from colloidal nanocrystals is a novel approach to sensitizing molecular triplets that are important for many applications. Recent studies suggest that this triplet transfer can be mediated by a hole transfer process when it is energetically allowed. In contrast, electron-transfer-mediated triplet transfer has not been observed yet, which is likely due to hole-trapping in typical II-VI group nanocrystals inhibiting the hole transfer step following initial electron transfer and hence disrupting a complete triplet exciton transfer. Here we report electron-transfer-mediated triplet energy transfer from CsPbCl3 and CsPbBr3 perovskite nanocrystals to surface-anchored rhodamine molecules. The mechanism was unambiguously established by ultrafast spectroscopy; control experiments using CdS nanocrystals also confirmed the role of hole-trapping in inhibiting this mechanism. The sensitized rhodamine triplets engaged in a variety of applications such as photon upconversion and singlet oxygen generation. Compared to conventional one-step triplet transfer, the electron-transfer-mediated mechanism is less demanding in terms of interfacial electronic coupling and hence is more generally implementable. Overall, this study not only establishes a complete framework of triplet energy transfer across nanocrystal/molecule interfaces but also greatly expands the scope of molecular triplet sensitization using nanocrystals.

Depressed Phase Transitions and Thermally Persistent Local Distortions in CsPbBr3 Quantum Dots

The optoelectronic properties of CsPbX3 quantum dots (where X = Cl, Br, or I) are influenced by both their local and average structures. Variable-temperature synchrotron X-ray diffraction measurements of CsPbBr3 quantum dots show tha

Room-temperature and gram-scale synthesis of CsPbX3 (X = Cl, Br, I) perovskite nanocrystals with 50-85% photoluminescence quantum yields

All inorganic CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (PNCs) with 50-85% photoluminescence quantum yields and tunable emission in the range of 440-682 nm have been successfully synthesized at room temperature in open air. This facile strategy enables us to prepare gram-scale CsPbBr3 NCs with a PLQY approaching 80%.

Growth and characterization of all-inorganic lead halide perovskite semiconductor CsPbBr3 single crystals

As a typical representative of all-inorganic lead halide perovskites, cesium lead bromide (CsPbBr3) has attracted significant attention in the context of photovoltaics and other optoelectronic applications in recent years. In this paper, CsPbBr3 single crystal growth was conducted by a creative electronic dynamic gradient (EDG) method. The crystal structure was systematically investigated using scientific instruments and equipment. X-ray diffraction techniques, including X-ray diffraction (XRD), temperature-dependent X-ray powder diffraction and the X-ray rocking curve, were used to identify the phase and to investigate phase transition rules. Electron diffraction techniques, including high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and electron backscatter diffraction (EBSD), were used to investigate the crystal micro-structure. The final results indicated that the grown CsPbBr3 crystal was a perfect single crystal preferentially orienting in the (110) direction and met the basic demand of its applications.

From Precursor Powders to CsPbX3 Perovskite Nanowires: One-Pot Synthesis, Growth Mechanism, and Oriented Self-Assembly

The colloidal synthesis and assembly of semiconductor nanowires continues to attract a great deal of interest. Herein, we describe the single-step ligand-mediated synthesis of single-crystalline CsPbBr3 perovskite nanowires (NWs) directly from the precursor powders. Studies of the reaction process and the morphological evolution revealed that the initially formed CsPbBr3 nanocubes are transformed into NWs through an oriented-attachment mechanism. The optical properties of the NWs can be tuned across the entire visible range by varying the halide (Cl, Br, and I) composition through subsequent halide ion exchange. Single-particle studies showed that these NWs exhibit strongly polarized emission with a polarization anisotropy of 0.36. More importantly, the NWs can self-assemble in a quasi-oriented fashion at an air/liquid interface. This process should also be easily applicable to perovskite nanocrystals of different morphologies for their integration into nanoscale optoelectronic devices.

Mesoporous Silica Particles Integrated with All-Inorganic CsPbBr3Perovskite Quantum-Dot Nanocomposites (MP-PQDs) with High Stability and Wide Color Gamut Used for Backlight Display

All-inorganic CsPbX3(X=I, Br, Cl) perovskite quantum dots (PQDs) have been investigated because of their optical properties, such as tunable wavelength, narrow band, and high quantum efficiency. These features have been used in light emitting diode (LED) devices. LED on-chip fabrication uses mixed green and red quantum dots with silicone gel. However, the ion-exchange effect widens the narrow emission spectrum. Quantum dots cannot be mixed because of anion exchange. We address this issue with a mesoporous PQD nanocomposite that can prevent ion exchange and increase stability. We mixed green quantum-dot-containing mesoporous silica nanocomposites with red PQDs, which can prevent the anion-exchange effect and increase thermal and photo stability. We applied the new PQD-based LEDs for backlight displays. We also used PQDs in an on-chip LED device. Our white LED device for backlight display passed through a color filter with an NTSC value of 113 % and Rec. 2020 of 85 %.

Environmentally-friendly synthesis of highly luminescent cesium lead halide perovskite nanocrystals using Sn-based halide precursors

In the last several years, cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) nanocrystals (NCs) have attracted much attention as promising kinds of optoelectronic and photonic materials. Via anion exchange reactions, the photoluminescence spectra of the CsPbX3 NCs can be tuned over nearly the entire visible spectral region. However, the preparation of the anion-exchange sources, mainly Pb-based halide precursors or oleylammonium halide precursors, would use large amounts of PbX2 (X = Cl, Br, I), trioetylphosphine (TOP) and HX (X = Cl, Br, I). These chemicals are toxic and environmentally-hazardous. To solve this problem, we report the synthesis of CsPbX3 (X = Cl, Br, I or mixed halides) NCs through modified anion exchange reactions. Using two kinds of Sn-based halide precursors as the anion-exchange sources, we can finely tune the chemical compositions and optical properties of pre-synthesized CsPbX3 NCs. Considering no PbX2, TOP and HX have been used in the preparation of the Sn-based halide precursors, we can determine this two-pot synthetic scheme as a step toward a green-chemistry approach for synthesizing high quality CsPbX3 NCs.

Solution-Phase Synthesis of Cesium Lead Halide Perovskite Nanowires

Halide perovskites have attracted much attention over the past 5 years as a promising class of materials for optoelectronic applications. However, compared to hybrid organic-inorganic perovskites, the study of their pure inorganic counterparts, like cesium lead halides (CsPbX3), lags far behind. Here, a catalyst-free, solution-phase synthesis of CsPbX3 nanowires (NWs) is reported. These NWs are single-crystalline, with uniform growth direction, and crystallize in the orthorhombic phase. Both CsPbBr3 and CsPbI3 are photoluminescence active, with composition-dependent temperature and self-trapping behavior. These NWs with a well-defined morphology could serve as an ideal platform for the investigation of fundamental properties and the development of future applications in nanoscale optoelectronic devices based on all-inorganic perovskites.

Amorphization-induced strong localization of electronic states in CsPbBr3 and CsPbCl3 studied by optical absorption measurements

Optical absorption spectra of amorphous CsPbX3 films (X=Br,Cl) are characterized by two Gaussian bands near the fundamental edge, with the optical energy gap largely blueshifted and the absorption intensity strongly reduced as compared with the crystalline films. The peak energies of the bands are close to those of the A and C bands of Pb-doped alkali halides. The spectral features are discussed in terms of a molecular orbital theory based on a quasicomplex Pb2+(X-)6 model similar to the complex model for the doped alkali halides. It is shown that not only Pb2+ 6s and 6p extended states near the band edges but also X- p states contributing to upper valence bands are localized by amorphization. The transitions from the localized Pb2+ 6s to 6p states produce the spin-orbit allowed 3P1 and dipole allowed 1P1 states responsible for the two Gaussians. The localized X- p states lie deeper in energy than the localized Pb2+ 6s state and only contribute to higher-energy absorption above the Gaussian bands, giving the reason for the reduced absorption near the fundamental edge. The blueshift of the optical energy gap is attributed to the disappearance of k dispersions for these one-electron states.

Perovskite as Recyclable Photocatalyst for Annulation Reaction of N-Sulfonyl Ketimines

A sustainable and cost-effective manner for the photocatalytic annulation reaction of N-sulfonyl ketimines with N-arylglycines to synthesize imidazolidine-fused sulfamidates (31 examples) by employing CsPbBr3 as a heterogeneous photocatalyst has been developed. The catalyst CsPbBr3 can be simply recovered from the reaction mixture and reused at least five times without an obvious reduction in its photocatalytic reactivity, exhibiting a high catalyst economic feature.

Photogeneration of thiyl radicals using metal-halide perovskite for highly efficient synthesis of thioethers

Recently, the use of metal-halide perovskite (MHP) for photoinduced organics transformation has attracted much attention. We report herein the development of photoinduced thiol-ene reaction using inorganic MHP of CsPbBr3 nanocrystal that is visible light-responsive, easy-to-prepare, and cost-effective. Under blue light-emitting diode (LED), a series of thiol substrates are demonstrated to be highly efficient reaction partners to couple with alkenes tolerated with various functional groups, affording diverse thioethers containing C–S bonds. The CsPbBr3-mediated thiol-ene reaction is characterized by high efficiency, broad substrate applicability, excellent yields, and mild conditions. Mechanism investigation shows that the visible light-excited CsPbBr3 induces the generation of thiyl radicals via hole oxidation to initiate the reaction, followed by redox neutral pathway and/or chain transfer pathway to accomplish thiol–olefin coupling. It is notable that CsPbBr3 exhibits advanced thiol-ene performance than that using MHP analogs and others. The work presents a new exploration of MHP-mediated transformation and shows great potential of MHPs for radical chemistry.

Performance enhancement of CsPbBr3 thin film-based light-emitting diodes by CsF-induced surface modification

Metal halide perovskites have been an attractive optoelectronic material for light-emitting diodes (LEDs) and display applications as well as photovoltaic devices. However, poor device performance and operation stability still impede their development and application. This paper reports a facile surface modification method to enhance the performance of CsPbBr3 thin film-based LEDs using CsF with various molar contents. Structural and chemical investigations showed that the CsF treatment removes the surface pinhole defects and fluorinates the CsPbBr3 surface simultaneously, which resulted in the enhanced photoluminescence intensity compared to the pristine one. The CsF treatment enhanced the LED performance by increasing the electroluminescence intensity while mitigating the saturation behavior, even under high applied bias. These outcomes were attributed to the advantageous roles of the CsF treatment, i.e., removal of surface pinhole defects, passivation of surface non-radiative defects, and the formation of an electron blocking layer.