Shape and dimensionality control by ligands is an efficient way to fabricate high-quality perovskite nanocrystals (NCs) with optoelectronic properties. Herein, to realize oriented transformations between different morphologies of CsPbBr3nanocrystals, we conceived of the use of defects and bidentate ligands to synergistically drive the reorientation of CsPbBr3nanocrystals into CsPbBr3nanowires (NWs). By employing aminocaproic acid as the bidentate ligand, CsPbBr3NWs were reconstructed from the CsPbBr3NCs (∼7 nm) with 20-60 nm in width and several micrometers in length, as well as a 527 nm photoluminescence (PL) peak, 59% PL quantum yield, and 98.5 ns PL lifetime. The bidentate ligand-directed anisotropic shape evolution and growth of perovskite NWs from NCs was elucidated by transmission electronmicroscopy and PL studies. The photodetectors fabricated with the reconstructed CsPbBr3NWs displayed a photocurrent enhancement (2.75 × 10-11A) compared with that of the devices based on solution-synthesized NWs (2.28 × 10-11A). The device also showed a short response time, indicating its more sensitive photoelectric response. This process provides a viable approach to engineering diverse morphologies of perovskite nanocrystals for optoelectronic applications.

Inorganic perovskite (CsPbX 3 , X = Cl, Br and I) nanocrystals (NCs) have received great attention for their fascinating optoelectronic properties. However, their potential applications are primarily limited by the instability arising from their mobile ionic nature. Herein, we demonstrate extremely stable CsPbX 3 nanocomposites (denoted as CsPbX 3 @CA-SiO 2 ) using a facile and effective templated synthetic strategy, by the in situ anchoring of CsPbX 3 NCs onto octadecyl-/propylamine-capped silica particles (SiO 2 NPs). The two-step synthesis involves first the preparation of amino-group-capped silica NPs from a mixed 3-aminopropyltriethoxysilane (APTES) and trimethoxy(octadecyl)silane (TMODS) precursor, which were utilized to induce the nucleation and growth of CsPbX 3 nanocrystals to produce CsPbX 3 @CA-SiO 2 composites with monodispersed CsPbX 3 NCs (∼6 nm). The emission wavelength of the resulting composite can be tuned between 400 nm and 650 nm by controlling the halide composition, while maintaining a high photoluminescence quantum yield (PLQY = 76%). The as-fabricated composites exhibited remarkable photostability and water stability, both uncommon in these materials. The CsPbX 3 @CA-SiO 2 composite can also be used to create an anti-counterfeit ink and down-converting white light emitting diode (WLED). This work provides a valuable approach for the production of future optoelectronic devices, catalysts and sensors based on perovskite NCs.

The potential optoelectronic applications of perovskite nanocrystals (NCs) are primarily limited by major material instability arising from the ionic nature of the NC lattice. Herein, we introduce a facile and effective strategy to prepare extremely stable CsPbX3 NC-polymer composites. NC surfaces are passivated with reactive methacrylic acid (MA) ligands, resulting in the formation of homogeneous nanocubes (abbreviated as MA-NCs) with a size of 14-17 nm and a photoluminescence quantum yield above 80%. The free double bonds on the surface then serve as chemically addressable synthetic handles, enabling UV-induced radical polymerization. Critically, a bromide-rich environment is developed to prevent NC sintering. The composites obtained from copolymerizing MA-NCs with hydrophobic methyl methacrylate and methacrylisobutyl polyhedral oligomeric silsesquioxane monomers exhibit enhanced properties compared to previously reported encapsulated NCs, including higher quantum yields, remarkable chemical stability toward water, and much enhanced thermal stability. The good solubility of the composite in organic solvent further enables its use as a solution-processable luminescent ink, used here for fabrication of white-light-emitting diodes with high luminous efficiency and excellent color-rendering index. The resulting fluorescent and stable NC ink opens the door to potential scalable and robust optoelectronic applications.

All-inorganic metal halide perovskite CsPbX3(X = Cl, Br, I) nanocrystals (NCs) have demonstrated attractive optoelectronic characteristics. However, their photocatalytic properties are limited by their poor stability and easy recombination of photogenerated carriers. Herein, we introduced a CsPbBr3@MSNs nanocomposite (CsPbBr3NCs embedded in dendritic mesoporous silica nanospheres (MSNs)) as photocatalysts for photoinduced electron transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The CsPbBr3nanocrystals (∼8.1 nm; PLQY of 62 ± 2.1%) were embedded in dendritic MSNs using a nanoconfinement strategy. PET-RAFT polymerization was successfully initiated using the CsPbBr3@MSNs nanocomposite as the photocatalyst. Reaction variables, such as catalyst loading, monomer composition, and excitation light wavelengths, were varied to yield polymers with the desired control of molecular weight and dispersity as well as block copolymers with high chain-end fidelity. In addition, the perovskite-based photocatalysts could be readily separated and purified, which allowed effective and rapid recycling of the nanocomposites for multiple polymerization cycles.

CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals (NCs) are known for their exceptional optoelectronic properties, yet the material's instability toward polar solvents, heat, or UV irradiation greatly limits its further applications. Herein, an efficient in situ growing strategy has been developed to give highly stable perovskite NC composites (abbreviated CsPbX3@CA-SiO2) by anchoring CsPbX3 NCs onto silica nanowires (NWs), which effectively depresses the optical degradation of their photoluminescence (PL) and enhances stability. The preparation of surface-functionalized serpentine silica NWs is realized by a sol-gel process involving hydrolysis of a mixture of tetraethyl orthosilicate (TEOS), 3-aminopropyltriethoxysilane (APTES), and trimethoxy(octadecyl)silane (TMODS) in a water/oil emulsion. The serpentine NWs are formed via an anisotropic growth with lengths up to 8 μm. The free amino groups are employed as surface ligands for growing perovskite NCs, yielding distributed monodisperse NCs (∼8 nm) around the NW matrix. The emission wavelength is tunable by simple variation of the halide compositions (CsPbX3, X = Cl, Br, or I), and the composites demonstrate a high photoluminescence quantum yield (PLQY 32-69%). Additionally, we have demonstrated the composites CsPbX3@CA-SiO2 can be self-woven to form a porous 3D hierarchical NWs membrane, giving rise to a superhydrophobic surface with hierarchical micro/nano structural features. The resulting composites exhibit high stability toward water, heat, and UV irradiation. This work elucidates an effective strategy to incorporate perovskite nanocrystals onto functional matrices as multifunctional stable light sources.

While convenient solution-based procedures have been realized for the synthesis of colloidal perovskite nanocrystals, the impact of surfactant ligands on the shape, size, and surface properties still remains poorly understood, which calls for a more detailed structure-morphology study. Herein we have systematically varied the hydrocarbon chain composition of carboxylic acids and amines to investigate the surface chemistry and the independent impact of acid and amine on the size and shape of perovskite nanocrystals. Solution phase studies on purified nanocrystal samples by (1)H NMR and IR spectroscopies have confirmed the presence of both carboxylate and alkylammonium ligands on surfaces, with the alkylammonium ligand being much more mobile and susceptible to detachment from the nanocrystal surfaces during polar solvent washes. Moreover, the chain length variation of carboxylic acids and amines, ranging from 18 carbons down to two carbons, has shown independent correlation to the size and shape of nanocrystals in addition to the temperature effect. We have additionally demonstrated that employing a more soluble cesium acetate precursor in place of the universally used Cs2CO3 results in enhanced processability without sacrificing optical properties, thus offering a more versatile recipe for perovskite nanocrystal synthesis that allows the use of organic acids and amines bearing chains shorter than eight carbon atoms. Overall our studies have shed light on the influence of ligand chemistry on crystal growth and stabilization of the nanocrystals, which opens the door to functionalizable perovskite nanocrsytals through surface ligand manipulation.

Ordered self-assembled arrays or superstructures of nanocrystals (NCs) have attracted intense research interest due to their ability to translate valuable nanoscale properties to larger length scales. Numerous techniques have been explored to induce self-assembly into various superstructures. Here we investigated a simple kinetic approach to form self-assembled one-dimensional perovskite CsPbX₃ (X: halides) nanocrystal arrays templated inside a pod shaped inert lead sulfate (PbSO₄) scaffold. Both the solvent effects, and the self-assembly process and mechanism, are systematically studied based on a uniform procedure developed to generate CsPbX₃ nanocrystal superlattices with different sizes and compositions. The formation of one-dimensional (1D) chains of NCs within a half-cylindrical pod of PbSO₄ reflects a balance between solvophobicity and solvophilicity of the components. By reducing the size of NCs, we successfully realized 2D superlattices with two or three rows of close-packed CsPbBr₃ NCs, in addition to single string-of-pearl type 1D assemblies. The superlattices can be assembled both inside and outside of the half-cylindrical shells by regulating the reaction conditions. The self-assembly behavior is reminiscent of the host-guest systems of organic molecular species where supramolecular recognition rules apply to give well-defined complexes. The current study opens a door for controlling self-assembled nanostructures of CsPbX₃ NCs, and provides an attainable platform for future optoelectronic devices.

Despite the exceptional optoelectronic characteristics of the emergent perovskite nanocrystals, the ionic nature greatly limits their stability, and thus restricts their potential applications. Here we have adapted a self-assembly strategy to access a rarely reported nanorod suprastructure that provide excellent encapsulation of perovskite nanocrystals by polymer-grafted graphene oxide layers. Polyacrylic acid-grafted graphene oxide (GO-g-PAA) was used as a surface ligand during the synthesis of the CsPbX₃ perovskite nanocrystals (NCs), yielding particles (5-12 nm) with tunable halide compositions that were homogeneously embedded in the GO-g-PAA matrix. The resulting NC-GO-g-PAA exhibits a higher photoluminescence quantum yield than previously reported encapsulated NCs while maintaining an easily tunable bandgap, allowing for emission spanning the visible spectrum. The NC-GO-g-PAA hybrid further self-assembles into well-defined nanorods upon solvent treatment. The resulting nanorod morphology imparts extraordinary chemical stability toward protic solvents such as methanol and water and much enhanced thermal stability. The introduction of barrier layers by embedding the perovskite NCs in the GO-g-PAA matrix, together with its unique assembly into nanorods, provides a novel strategy to afford robust perovskite emissive materials with environmental stability that may meet or exceed the requirement for optoelectronic applications.

All-inorganic CsPbX₃ (X = Cl, Br or I) perovskite nanocrystals have attracted extensive interest recently due to their exceptional optoelectronic properties. In an effort to improve the charge separation and transfer following efficient exciton generation in such nanocrystals, novel functional nanocomposites were synthesized by the in situ growth of CsPbBr₃ perovskite nanocrystals on two-dimensional MXene nanosheets. Efficient excited state charge transfer occurs between CsPbBr₃ NCs and MXene nanosheets, as indicated by significant photoluminescence (PL) quenching and much shorter PL decay lifetimes compared with pure CsPbBr₃ NCs. The as-obtained CsPbBr₃/MXene nanocomposites demonstrated increased photocurrent generation in response to visible light and X-ray illumination, attesting to the potential application of these heterostructure nanocomposites for photoelectric detection. The efficient charge transfer also renders the CsPbBr₃/MXene nanocomposite an active photocatalyst for the reduction of CO₂ to CO and CH₄. This work provides a guide for exploration of perovskite materials in next-generation optoelectronics, such as photoelectric detectors or photocatalyst.

Creating highly stable inorganic perovskite nanocrystals (CsPbX₃, where X = Cl, Br, and I) with excellent optical performance is challenging because their optical properties depend on their ionic structure and its inherent defects. Here, we present a facile and effective synthesis using a nanoconfinement strategy to grow Mn²⁺-doped CsPbCl₃ nanocrystals embedded in dendritic mesoporous silica nanospheres (MSNs). The resulting nanocomposite is abbreviated as Cs(Pb _x/Mn_{1- x})Cl₃@MSNs and can serve as the orange emitter for white light-emitting diodes (WLEDs). The MSN matrix was prepared via a templated sol-gel technique as monodispersed center-radial dendritic porous particles, with a diamater of ∼105 nm and an inner pore size of ∼13 nm. The MSN was then utilized as the matrix to initiate the growth of Mn-doped perovskite nanocrystals (NCs). The NCs in the resulting composite have an average diameter of 8 nm and a photoluminescence quantum yield of >30%. In addition, the optical properties of the Cs(Pb _x/Mn_{1- x})Cl₃@MSNs can be tuned by varying the Mn²⁺ doping level. The resulting composites presented a significantly improved resistance to ultraviolet (UV) light, temperature, and moisture compared to that of bare Cs(Pb_0.72/Mn_0.28)Cl₃. Finally, we fabricated down-converting WLEDs by using Cs(Pb _x/Mn_{1- x})Cl₃@MSNs as the orange-emitting phosphor deposited onto UV-emitting chips, demonstrating their promising applications in solid-state lighting. This work provides a valuable approach to fabricating stable orange luminophores as replacements for traditional emitters in light-emitting diode devices.