Near-unity quantum yield and long-term emission stability in halide perovskite nanocrystal glass composite

Metal halide perovskites are promising optoelectronic materials due to their outstanding luminescent properties. However, the instability of perovskites has long been the bottleneck to their practical applications. Here Cs4PbBr6 nanocrystals based glass composite (Cs4PbBr6 NCs@glass) are successfully prepared, which displays green emission color (520 nm), narrow bandwidth (23 nm) and a near-unity photoluminescence quantum yield (PLQY). The H2O molecules permeating in the lattice of Cs4PbBr6 were found to be a crucial role in the subband energy emission. The Cs4PbBr6 NCs@glass has excellent emission stability; maintains 93 % of initial PL intensity after ultraviolet light irradiation for over 5000 h. In addition, by adjusting the halogen content, we have achieved tunable emission color from blue (450 nm) to green (520 nm) and red (670 nm) on Cs4PbX6 NCs@glass (X = Cl, Br, I), which covers up to 127 % of the National Television Systems Board (NTSC) standard system. Our finding indicates the commercial applications of perovskite materials in lighting and display.

Encapsulation engineering of porous crystalline frameworks for delayed luminescence and circularly polarized luminescence

Delayed luminescence (DF), including phosphorescence and thermally activated delayed fluorescence (TADF), and circularly polarized luminescence (CPL) exhibit common and broad application prospects in optoelectronic displays, biological imaging, and encryption. Thus, the combination of delayed luminescence and circularly polarized luminescence is attracting increasing attention. The encapsulation of guest emitters in various host matrices to form host-guest systems has been demonstrated to be an appealing strategy to further enhance and/or modulate their delayed luminescence and circularly polarized luminescence. Compared with conventional liquid crystals, polymers, and supramolecular matrices, porous crystalline frameworks (PCFs) including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), zeolites and hydrogen-bonded organic frameworks (HOFs) can not only overcome shortcomings such as flexibility and disorder but also achieve the ordered encapsulation of guests and long-term stability of chiral structures, providing new promising host platforms for the development of DF and CPL. In this review, we provide a comprehensive and critical summary of the recent progress in host-guest photochemistry via the encapsulation engineering of guest emitters in PCFs, particularly focusing on delayed luminescence and circularly polarized luminescence. Initially, the general principle of phosphorescence, TADF and CPL, the combination of DF and CPL, and energy transfer processes between host and guests are introduced. Subsequently, we comprehensively discuss the critical factors affecting the encapsulation engineering of guest emitters in PCFs, such as pore structures, the confinement effect, charge and energy transfer between the host and guest, conformational dynamics, and aggregation model of guest emitters. Thereafter, we summarize the effective methods for the preparation of host-guest systems, especially single-crystal-to-single-crystal (SC-SC) transformation and epitaxial growth, which are distinct from conventional methods based on amorphous materials. Then, the recent advancements in host-guest systems based on PCFs for delayed luminescence and circularly polarized luminescence are highlighted. Finally, we present our personal insights into the challenges and future opportunities in this promising field.

Hydrogen-Bonded Cocrystals Encapsulating CsPbBr3 Perovskite Nanocrystals with Enhancement of Charge Transport for Photocatalytic Reduction of Uranium

At present, poor stability and carrier transfer efficiency are the main problems that limit the development of perovskite-based photoelectric technologies. In this work, hydrogen-bonded cocrystal-coated perovskite composite (PeNCs@NHS-M) is easily obtained by inducing rapid crystallization of melamine (M) and N-hydroxysuccinimide (NHS) with PeNCs as the nuclei. The outer NHS-M cocrystal passivates the undercoordinated lead atoms by forming covalent bonds, thereby greatly reducing the trap density while maintaining good structure stability for perovskite nanocrystals. Moreover, benefiting from the interfacial covalent band linkage and long-range ordered structures of cocrystals, the charge transfer efficiency is effectively enhanced and PeNCs@NHS-M displays superior photoelectric performance. Based on the excellent photoelectric performance and abundant active sites of PeNCs@NHS-M, photocatalytic reduction of uranium is realized. PeNCs@NHS-M exhibits U(VI) reduction removal capability of up to 810.1 mg g-1 in the presence of light. The strategy of cocrystals trapping perovskite nanocrystals provides a simple synthesis method for composites and opens up a new idea for simultaneously improving the stability and photovoltaic performance of perovskite.

Confinement of CsPbBr3 Perovskite Nanocrystals into Extra-large-pore Zeolite for Efficient and Stable Photocatalytic Hydrogen Evolution

Metal halide perovskites (MHPs), renowned for their outstanding optoelectronic properties, hold significant promise as photocatalysts for hydrogen evolution reaction (HER). However, the low stability and insufficient exposure of catalytically active sites of bulky MHPs seriously impair their catalytic efficiency. Herein, we utilized an extra-large-pore zeolite ZEO-1 (JZO) as a host to confine and stabilize the CsPbBr3 nanocrystals (3.4 nm) for boosting hydrogen iodide (HI) splitting. The as-prepared CsPbBr3@ZEO-1 featured sufficiently exposed active sites, superior stability in acidic media, along with intrinsic extra-large pores of ZEO-1 that were favorable for molecule/ion adsorption and diffusion. Most importantly, the unique nanoconfinement effect of ZEO-1 led to the narrowing of the band gap of CsPbBr3, allowing for more efficient light utilization. As a result, the photocatalytic HER rate of the as-prepared CsPbBr3@ZEO-1 photocatalyst was increased to 1734 μmol ⋅ h-1 ⋅ g-1 (CsPbBr3) under visible light irradiation compared with bulk CsPbBr3 (11 μmol ⋅ h-1 ⋅ g-1 (CsPbBr3)), and the long-term durability (36 h) can be achieved. Furthermore, Pt was incorporated with well-dispersed CsPbBr3 nanocrystals into ZEO-1, resulting in a significant enhancement in activity (4826 μmol ⋅ h-1 ⋅ g-1 (CsPbBr3)), surpassing most of the Pt-integrated perovskite-based photocatalysts. Density functional theory (DFT) calculations and charge-carrier dynamics investigation revealed that the dramatically boosted photocatalytic performance of Pt/CsPbBr3@ZEO-1 could be attributed to the promotion of charge separation and transfer, as well as to the substantially lowered energy barrier for HER. This work highlights the advantage of extra-large-pore zeolites as the nanoscale platform to accommodate multiple photoactive components, opening up promising prospects in the design and exploitation of novel zeolite-confined photocatalysts for energy harvesting and storage.

Alkali-Metal-Assisted Green-Solvent Synthesis for In Situ Growth of Perovskite Nanocrystals in Porous Materials

Inorganic metal halide perovskite CsPbX3 (X = I, Br, and Cl) nanocrystals (NCs) are rapidly developed due to their excellent photophysical properties and potential applications in lighting, lasers, and scintillators. However, the materials for growing perovskite NCs are insoluble or hydrolyzed in most green solvents, limiting their further development. Based on rational chemical analysis, an alkali-metal-assisted green-solvent synthesis method for in situ growth of CsPbBr3 NCs within SAPO-34 zeolite with bright luminescence is developed. Water is the only solvent used in the whole process. Surprisingly, by the synergistic effect of the channel structure of SAPO-34 and alkali-metal ions crystallization regulation, the CsPbBr3 NCs embedded in SAPO-34 assisted by Na+ emit bright blue light under ultraviolet illumination, with a 30 nm blue shift comparing to the CsPbBr3 NCs assisted by K+. Moreover, CsPbBr3 NCs can also be grown in mesoporous SiO2 SBA-15 and zeolites including ZSM-5, AlPO-5, and SOD, indicating that the method is universal for in situ growth of luminescent perovskite NCs in porous materials. This alkali-metal-assisted green-solvent synthesis provides a new strategy for developing high-quantum-yield, tunable-emission, and stable perovskite luminescent materials.

Hydrogen-Bonded Organic Cocrystal-Encapsulated Perovskite Nanocrystals as Coreactant-Free Electrochemiluminescent Luminophore for the Detection of Uranium

Lead halide perovskite nanocrystals with excellent photophysical properties are promising electrochemiluminescence (ECL) candidates, but their poor stability greatly restricts ECL applications. Herein, hydrogen-bonded cocrystal-encapsulated CsPbBr3 perovskite nanocrystals (PeNCs@NHS-M) were synthesized by using PeNCs as nuclei for inducing the crystallization of melamine (M) and N-hydroxysuccinimide (NHS). The as-synthesized composite exhibits multiplicative ECL efficiencies (up to 24-fold that of PeNCs) without exogenous coreactants and with excellent stability in the aqueous phase. The enhanced stability can be attributed to the well-designed heterostructure of the PeNCs@NHS-M composite, which benefits from both moiety passivation and protection of the peripheral cocrystal matrix. Moreover, the heterostructure with covalent linkage facilitates charge transfer between PeNCs and NHS-M cocrystals, realizing effective ECL emission. Meanwhile, the NHS and M components act as coreactants for PeNCs, shortening the electron-transport distance and resulting in a significant increase in the ECL signal. Furthermore, by taking advantage of the specific binding effect between NHS-M and uranyl (UO22+), an ECL system with both a low detection limit (1 nM) and high selectivity for monitoring UO22+ in mining wastewater is established. The presence of UO22+ disrupted the charge-transfer effect within PeNCs@NHS-M, weakening the ECL signals. This work provides an efficient design strategy for obtaining stable and efficient ECLs from perovskite nanocrystals, offering a new perspective for the discovery and application of perovskite-based ECL systems.

Metal Clusters Confined in Chiral Zeolitic Imidazolate Framework for Circularly Polarized-Luminescence Inks

Chiroptical activities arising in nanoclusters (NCs) are emerging as one of the most dynamic areas of modern science. However, devising an overarching strategy that is capable of concurrently enhancing the photoluminescence (PL) and circularly polarized luminescence (CPL) of metal NCs remains a formidable challenge. Herein, gold and silver nanoclusters (AuNCs, AgNCs) are endowed with CPL, for the first time, through a universal host-guest approach─centered around perturbing a chiral microenvironment within chiral hosts, simultaneously enhancing emissions. Remarkably, the photoluminescence quantum yield (PLQY) of AuNCs has undergone an increase of over 200 times upon confinement, escalating from 0.05% to 12%, and demonstrates a CPL response. Moreover, a three-dimensional (3D) model termed "NCs@CMOF" featuring CPL activity is created using metal cluster-based assembly inks through the process of 3D printing. This work introduces a potentially straightforward and versatile approach for achieving both PL enhancement and CPL activities in metal clusters.

Halide Perovskites and Their Derivatives for Efficient, High-Resolution Direct Radiation Detection: Design Strategies and Applications

The past decade has witnessed a rapid rise in the performance of optoelectronic devices based on lead-halide perovskites (LHPs). The large mobility-lifetime products and defect tolerance of these materials, essential for optoelectronics, also make them well-suited for radiation detectors, especially given the heavy elements present, which is essential for strong X-ray and γ-ray attenuation. Over the past decade, LHP thick films, wafers, and single crystals have given rise to direct radiation detectors that have outperformed incumbent technologies in terms of sensitivity (reported values up to 3.5 × 106 µC Gyair -1 cm-2 ), limit of detection (directly measured values down to 1.5 nGyair s-1 ), along with competitive energy and imaging resolution at room temperature. At the same time, lead-free perovskite-inspired materials (e.g., methylammonium bismuth iodide), which have underperformed in solar cells, have recently matched and, in some areas (e.g., in polarization stability), surpassed the performance of LHP detectors. These advances open up opportunities to achieve devices for safer medical imaging, as well as more effective non-invasive analysis for security, nuclear safety, or product inspection applications. Herein, the principles behind the rapid rises in performance of LHP and perovskite-inspired material detectors, and how their properties and performance link with critical applications in non-invasive diagnostics are discussed. The key strategies to engineer the performance of these materials, and the important challenges to overcome to commercialize these new technologies are also discussed.

Interfacial alloying between lead halide perovskite crystals and hybrid glasses

The stellar optoelectronic properties of metal halide perovskites provide enormous promise for next-generation optical devices with excellent conversion efficiencies and lower manufacturing costs. However, there is a long-standing ambiguity as to whether the perovskite surface/interface (e.g. structure, charge transfer or source of off-target recombination) or bulk properties are the more determining factor in device performance. Here we fabricate an array of CsPbI3 crystal and hybrid glass composites by sintering and globally visualise the property-performance landscape. Our findings reveal that the interface is the primary determinant of the crystal phases, optoelectronic quality, and stability of CsPbI3. In particular, the presence of a diffusion "alloying" layer is discovered to be critical for passivating surface traps, and beneficially altering the energy landscape of crystal phases. However, high-temperature sintering results in the promotion of a non-stoichiometric perovskite and excess traps at the interface, despite the short-range structure of halide is retained within the alloying layer. By shedding light on functional hetero-interfaces, our research offers the key factors for engineering high-performance perovskite devices.

Stabilizing Metal Halide Perovskites for Solar Fuel Production: Challenges, Solutions, and Future Prospects

Metal halide perovskites (MHPs) are emerging photocatalyst materials that can enable sustainable solar-to-chemical energy conversion by virtue of their broad absorption spectra, effective separation/transport of photogenerated carriers, and solution processability. Although preliminary studies show the excellent photocatalytic activities of MHPs, their intrinsic structural instability due to the low formation energy and soft ionic nature is an open challenge for their practical applications. This review discusses the latest understanding of the stability issue and strategies to overcome this issue for MHP-based photocatalysis. First, the origin of the instability issue at atomic levels and the design rules for robust structures are analyzed and elucidated. This is then followed by presenting several different material design strategies for stability enhancement, including reaction medium modification, material surface protection, structural dimensionality engineering, and chemical composition engineering. Emphases are placed on understanding the effects of these strategies on photocatalytic stability as well as the possible structure-performance correlation. Finally, the possible future research directions for pursuing stable and efficient MHP photocatalysts in order to accelerate their technological maturity on a practical scale are outlined. With that, it is hoped to provide readers a valuable snapshot of this rapidly developing and exciting field.

Ultrasmall water-stable CsPbBr3 quantum dots with high intensity blue emission enabled by zeolite confinement engineering

Ultrasmall CsPbBr3 perovskite quantum dots (PQDs) as promising blue-emitting materials are highly desired for full-color display and lighting applications, but their inferior efficiency and poor ambient stability hinder extensive applications. Herein, a "break-and-repair" strategy has been developed to tightly confine monodispersed ultrasmall CsPbBr3 PQDs in a zeolite. In this strategy, the CsPbBr3 PQDs are introduced into the zeolite via a high temperature evaporation method, wherein the perovskite precursors break the zeolite framework, and amino acids and silane are then used to fix the damaged framework and lock the perovskite QDs within the matrix. By modulating the synthetic conditions to control the growth of CsPbBr3, PQDs with ultrasmall size of 2 nm have been obtained in the zeolite, giving emission centered at 460 nm with a high quantum yield of 76.93%. Strikingly, the PQDs@zeolite composite exhibits water-induced reversible photoluminescence promoted by the coordination between the amino acids and PQDs in a dynamic manner, achieving enhanced water stability (14 days in aqueous solution). This work provides a new perspective for the synthesis of water-stable blue-emitting perovskite composites for potential applications in lighting fields.

Strategies to Extend the Lifetime of Perovskite Downconversion Films for Display Applications

Metal halide perovskite nanocrystals (PeNCs) have outstanding luminescent properties that are suitable for displays that have high color purity and high absorption coefficient; so they are evaluated for application as light emitters for organic light-emitting diodes, light-converters for downconversion displays, and future near-eye augmented reality/virtual reality displays. However, PeNCs are chemically vulnerable to heat, light, and moisture, and these weaknesses must be overcome before devices that use PeNCs can be commercialized. This review examines strategies to overcome the low stability of PeNCs and thereby permit the fabrication of stable downconversion films, and summarizes downconversion-type display applications and future prospects. First, methods to increase the chemical stability of PeNCs are examined. Second, methods to encapsulate PeNC downconversion films to increase their lifetime are reviewed. Third, methods to increase the long-term compatibility of resin with PeNCs, and finally, how to secure stability using fillers added to the resin are summarized. Fourth, the method to manufacture downconversion films and the procedure to evaluate their reliability for commercialization is then described. Finally, the prospects of a downconversion system that exploits the properties of PeNCs and can be employed to fabricate fine pixels for high-resolution displays and for near-eye augmented reality/virtual reality devices are explored.

Effective Suppressing Phase Segregation of Mixed-Halide Perovskite by Glassy Metal-Organic Frameworks

Lead mixed-halide perovskites offer tunable bandgaps for optoelectronic applications, but illumination-induced phase segregation can quickly lead to changes in their crystal structure, bandgaps, and optoelectronic properties, especially for the Br-I mixed system because CsPbI3 tends to form a non-perovskite phase under ambient conditions. These behaviors can impact their performance in practical applications. By embedding such mixed-halide perovskites in a glassy metal-organic framework, a family of stable nanocomposites with tunable emission is created. Combining cathodoluminescence with elemental mapping under a transmission electron microscope, this research identifies a direct relationship between the halide composition and emission energy at the nanoscale. The composite effectively inhibits halide ion migration, and consequently, phase segregation even under high-energy illumination. The detailed mechanism, studied using a combination of spectroscopic characterizations and theoretical modeling, shows that the interfacial binding, instead of the nanoconfinement effect, is the main contributor to the inhibition of phase segregation. These findings pave the way to suppress the phase segregation in mixed-halide perovskites toward stable and high-performance optoelectronics.

All-inorganic lead halide perovskite nanocrystals applied in advanced display devices

Advanced display devices are in greater demand due to their large color gamut, high color purity, ultrahigh visual resolution, and small size pixels. All-inorganic lead halide perovskite (AILHP) nanocrystals (NCs) possess inherent advantages such as narrow emission width, saturated color, and flexible integration, and have been developed as functional films, light sources, backlight components, and display panels. However, some drawbacks still restrict the practical application of advanced display devices based on AILHP NCs, including working stability, large-scale synthesis, and cost. In this review, we focus on AILHP NCs, review the recent progress in materials synthesis, stability improvement, patterning techniques, and device application. We also highlight the important role of materials systems in creating advanced display devices, followed by the challenges and opportunities in industrial processes. This review provides beneficial inspiration for the future development of AILHP NCs in colorful and white backlight, as well as high resolution full-color displays.

In situgrowth strategy to construct perovskite quantum dot@covalent organic framework composites with enhanced water stability

Metal halide perovskite quantum dots (QDs) have excellent optoelectronic properties; however, their poor stability under water or thermal conditions remains an obstacle to commercialization. Here, we used a carboxyl functional group (-COOH) to enhance the ability of a covalent organic framework (COF) to adsorb lead ions and grow CH₃NH₃PbBr₃(MAPbBr₃) QDsin situinto a mesoporous carboxyl-functionalized COF to construct MAPbBr₃QDs@COF core-shell-like composites to improve the stability of perovskites. Owing to the protection of the COF, the as-prepared composites exhibited enhanced water stability, and the characteristic fluorescence was maintained for more than 15 d. These MAPbBr₃QDs@COF composites can be used to fabricate white light-emitting diodes with a color comparable to natural white emission. This work demonstrates the importance of functional groups for thein situgrowth of perovskite QDs, and coating with a porous structure is an effective way to improve the stability of metal halide perovskites.

CsPbBr3 perovskite quantum dots grown within Fe-doped zeolite X with improved stability for sensitive NH3 detection

All-inorganic cesium lead halide (CsPbX₃, X = Cl, Br and I) perovskite quantum dots (QDs) have received enormous research interest because of their exceptional optoelectronic properties, but their low chemical stability under ambient conditions from inevitable defects restricts their practical applications. In an effort to enhance the stability of QDs, in this study, novel functional nanocomposites were fabricated by encapsulating perovskite QDs with zeolite X doped with iron ions. Focusing on the as-obtained nanocomposites labeled with QDs@Fe/X-n, doping a reasonable amount of Fe³⁺ ions can tremendously improve the order of perovskite lattices and reduce the halide vacancies. The results of stability improvement in nanocomposites with an optimal Fe³⁺ load (QDs@Fe/X-3) are presented. After storage in air for 100 days, the emission-peak position of the composites can remain almost unchanged, and the photoluminescence (PL) intensity can reach ∼98% of the original intensity. Additionally, the PL intensity of QDs@Fe/X-3 can decrease immediately when exposing it to a NH₃ atmosphere at room temperature. The PL intensity can be linearly varied with a change in the NH₃ concentration. The original value of the PL can be rapidly recovered by separating the sample from the NH₃ environment. This work enables the QDs@Fe/X composite to be an ideal active material for ammonia sensing.

Interfacial engineering of halide perovskites and two-dimensional materials

Recently, halide perovskites (HPs) and layered two-dimensional (2D) materials have received significant attention from industry and academia alike. HPs are emerging materials that have exciting photoelectric properties, such as a high absorption coefficient, rapid carrier mobility and high photoluminescence quantum yields, making them excellent candidates for various optoelectronic applications. 2D materials possess confined carrier mobility in 2D planes and are widely employed in nanostructures to achieve interfacial modification. HP/2D material interfaces could potentially reveal unprecedented interfacial properties, including light absorbance with desired spectral overlap, tunable carrier dynamics and modified stability, which may lead to several practical applications. In this review, we attempt to provide a comprehensive perspective on the development of interfacial engineering of HP/2D material interfaces. Specifically, we highlight the recent progress in HP/2D material interfaces considering their architectures, electronic energetics tuning and interfacial properties, discuss the potential applications of these interfaces and analyze the challenges and future research directions of interfacial engineering of HP/2D material interfaces. This review links the fields of HPs and 2D materials through interfacial engineering to provide insights into future innovations and their great potential applications in optoelectronic devices.

Weakening Ligand-Liquid Affinity to Suppress the Desorption of Surface-Passivated Ligands from Perovskite Nanocrystals

The interfacial migration of surface-bound ligands highly affects the colloidal stability and optical quality of semiconductor nanocrystals, of which the underlying mechanism is not fully understood. Herein, colloidal CsPbBr₃ perovskite nanocrystals (PNCs) with fragile dynamic equilibrium of ligands are taken as the examples to reveal the important role of balancing ligand-solid/solvent affinity in suppressing the desorption of ligands. As a micellar surfactant, glycyrrhizic acid (GA) with bulky hydrophobic and hydrophilic groups exhibits a relatively smaller diffusion coefficient (∼440 μm²/s in methanol) and weaker ligand-liquid affinity than that of conventional alkyl amine and carboxy ligands. Consequently, hydrophilic GA-passivated PNCs (PNCs-GA) show excellent colloidal stability in various polar solvents with dielectric constant ranging from 2.2 to 32.6 and efficient photoluminescence with a quantum yield of 85.3%. Due to the suppressed desorption of GA, the morphological and optical properties of PNCs-GA are well maintained after five rounds purification and two months long-term storage. At last, hydrophilic PNCs-GA are successfully patterned through inkjet- and screen-printing technology. These findings offer deep insights into the interfacial chemistry of colloidal NCs and provide a universal strategy for preparing high-quality hydrophilic PNCs.

Multiple Interpenetrating Metal-Organic Frameworks with Channel-Size-Dependent Behavior for Selective Gossypol Detection and Perovskite Quantum Dot Encapsulation

An interpenetrating structure endows metal-organic frameworks (MOFs) with many exciting applications, such as fluorescence detection and host-guest chemistry. Herein, two unique structure-interpenetrating In-MOFs (In-pdda-1 and In-pdda-2; H2pdda = 4,4'-(pyridine-2,5-diyl)dibenzoic acid) are constructed by different coordination configurations. The four-connected In3+ center shows a triangular-pyramidal configuration or a 2D rectangle, forming an unc topology for In-pdda-1 and a sql network for In-pdda-2, respectively. Two different interpenetrating modes created by linear rigid ligands and metal clusters are observed in the two MOFs (In-pdda-1, 8-fold interpenetrating mode; In-pdda-2, [2D + 2D] interpenetrating mode), which determine the channel-size-dependent properties in fluorescence applications. During the quantitative detection process of gossypol, the small rhombic channels divided by interpenetrating molecular planes of In-pdda-2 greatly limit the distance between the analyte and the probe, promoting electron transfer and energy transfer processes and thus resulting in a low detection limit (28.6 nM). In addition, the pore size effect of In-pdda-1 encouraged us to explore an in situ perovskite quantum dot encapsulation strategy to obtain a MAPbBr3@MOF material with tunable and stable luminescence properties. Both of the above channel-size-dependent fluorescence properties may provide inspiration for the structural design and specialized applications of MOF materials.

Spontaneous Formation of Lead-Free Cs3 Cu2 I5 Quantum Dots in Metal-Organic-Frameworks with Deep-Blue Emission

All-inorganic lead-free Cs₃ Cu₂ I₅  perovskite-derivant quantum dots (QDs) have attracted tremendous attention due to their nontoxicity and unique optoelectronic properties. However, the traditional hot-injection method requires high temperatures and multiple ligands to confine the growth of QDs. Herein, a strategy is reported to spontaneously synthesize ultrasmall Cs₃ Cu₂ I₅  QDs within metal-organic-frameworks (MOFs) MOF-74 at room temperature (RT) with an average diameter of 4.33 nm. The obtained Cs₃ Cu₂ I₅  QDs exhibit an evident deep-blue emission with Commission Internationale de L'Eclairage coordinates of (0.17, 0.07), owing to the strong quantum confinement effect. Due to the protection of MOF-74, the Cs₃ Cu₂ I₅  QDs demonstrate superior stability, and the photoluminescence quantum yield retains 89% of the initial value after the storage of 1440 h under the environment with relative humidity exceeding 70%. Besides, triplet-triplet annihilation upconversion emission is observed within the composite of Cs₃ Cu₂ I₅ @MOF-74, which brings out apparent temperature-dependent photoluminescence. This study reveals a facile method for fabricating ultrasmall lead-free perovskite-derivant QDs at RT without multiple ligands. Besides, the temperature-dependent photoluminescence of Cs₃ Cu₂ I₅ @MOF-74 may open up a new way to develop the applications of temperature sensors or other related optoelectronic devices.

Ultra-Thermostability of Spatially Confined and Fully Protected Perovskite Nanocrystals by In Situ Crystallization

Although all-inorganic perovskite materials present multiple fascinating optical properties, their poor stability undermines their potential application in the field of multi-color display. Herein, spatially confined CsPbBr₃ nanocrystals are in situ crystallized within uniform mesoporous SiO₂ nanospheres (MSNs) to regulate their size distribution, passivate their surface defects, shield them from water/oxygen, and more importantly, enhance their thermotolerance. As a result, the remnant PL intensity of the prepared spatially confined perovskite (CsPbBr₃ ) nanocrystals by in situ crystallization within uniform mesoporous SiO₂ nanospheres (SCP@MSNs) powders can be maintained over 98% of its initial value even after being immersed in harsh conditions (0.1 m HCl or 0.1 m NaOH) for 60 days. Furthermore, the prepared SCP@MSNs-PDMS film demonstrates astonishing thermostability by maintaining almost consistent room temperature PL intensities after continuous heating-cooling cycles between 200 and 25 °C, which would greatly improve its processability during potential industrial manufacturing. The fabricated LCD backlit based on SCP@MSNs covers 124% of NTSC standard and 95.6% of Rec. 2020 standard, indicating its great potential in practical display field.

Ultra-Stable CsPbX3 @Pyrophosphate Nanoparticles in Water over One Year

All-inorganic lead halide perovskite (CsPbX₃ , X = Cl, Br, I, or their mixture) nanocrystals (NCs) have achieved inspiring advancements in optoelectronic fields but still suffer from poor durability when exposed to environmental stimuli such as water, irradiation and heat. Herein, a strategy of employing pyrophosphate as the inert shell for CsPbX₃ NCs is reported. The strong binding between pyrophosphate and CsPbBr₃ surface can stabilize the perovskite structure well. The as-obtained core@shell CsPbBr₃ @NH₄ AlP₂ O₇ NCs exhibit impressive stability against water and maintain the initial optical properties with negligible change in 400 days. Furthermore, significant improvement of irradiation/thermal resistance is realized due to the protecting role of pyrophosphate. The NCs can retain 100% and ≈90% of the original PL after hundreds of heating/cooling cycles and several hundred hours of UV light irradiation, respectively. As a result, the core@shell products can be directly used for high-resolution inkjet printing, enabling the printed fluorescent information to be resistant under harsh environmental conditions. This work provides a promising way for the synthesis of highly stable encapsulated perovskite NCs and demonstrates a great potential in practical applications.

Multiple Responsive CPL Switches in an Enantiomeric Pair of Perovskite Confined in Lanthanide MOFs

Circularly polarized luminescence (CPL) switches have attracted widespread attention due to their potential applications in advanced information technologies. However, the design and fabrication of solid-state multiple-responsive CPL switches remain challenging. Here, through self-assembly of chiral metal-organic frameworks (MOFs) and perovskite nanocrystals (NCs), a pair of crystalline enantiomeric (P)-(+)/(M)-(-)-EuMOF⊃MAPbX₃ (MA = CH₃ NH₃ ⁺ , X = Cl^- , Br^- , I^- ) adducts is prepared, where the achiral MAPbBr₃ perovskite NCs embedded into chiral MOFs inherit the chirality of host MOFs by host-guest EuBr and PbO coordination bonds, which is demonstrated by synchrotron-radiation-based X-ray absorption spectroscopy. The chiral adducts show enhanced photoluminescence quantum yield (PLQY), good thermal stability of CPL in air, and photoswitchable CPL properties upon altering different UV irradiation. Based on two chiral emission centers and their different characteristics, reversible CPL switches are realized upon a diversity of external stimuli, for example, chemicals (water /CH₃ NH₃ Br solution) or temperatures (room temperature/high temperature). Benefiting from the extraordinary stimuli-responsive and highly reversible switchable CPL, multiple information encryptions and decryptions integrated with CPL, together with a chiroptical logic gate are successfully designed. This work opens a new avenue to generally fabricate solid-state CPL composite materials and develops new applications based on switchable CPL.

Understanding the Energy Barriers of the Reversible Ion Exchange Process in CsPbBr1.5Cl1.5@Y2O3:Eu3+ Macroporous Composites and Their Application in Anti-Counterfeiting Codes

The photoinduced reversible ion exchanges in mixed halide perovskites and the resulting luminescent variations make them promising for constructing anti-counterfeiting patterns; however, its understanding in an interfacial view is lacking. In this work, nominal CsPbBr_1.5Cl_1.5 (CPBC) nanocrystals (NCs) were introduced into macroporous Y₂O₃:Eu³⁺ (MYE) to realize emission color variations from red emission of MYE to green emission of halide NCs. The large surface area of MYE helps the formation of Y-Cl/Br bonds which induces fluctuation in the halide composition, while water and intrinsic halogen defects have also been proved to be essential in the reversible ion segregation process. The PL variations of several samples with different pore sizes were investigated upon irradiation of light with different photon energies and excitation power at certain temperatures. According to combined results of density functional theory calculation, the research reveals the presence of two energy barriers that would be overcome correspondingly by the excitation photon and the concentration difference in the ion exchange and recovery process. A photochromic anti-counterfeiting quick response (QR) code was constructed facilely with the perovskite composites. This work provides a deeper understanding from the interfacial aspect and also proposes a feasible strategy to realize reversible PL variation for anti-counterfeiting applications.

Clusters of Cesium-Lead-Iodide Perovskites in the Zeolite Matrix

Small clusters of cesium-lead-iodide perovskites (CLIPs) have been prepared in the Na-X zeolite matrix and studied by means of spectroscopy and quantum chemical modeling. Regularity of pores in single crystals of zeolite assures the formation of clusters of a certain size. By the first-principles quantum chemical calculations, we have determined that clusters Cs₄PbI₆, Cs₅Pb₂I₉, and probably Cs₇Pb₅I₁₆ with a size of 0.74, 1.29, and 1.36 nm, respectively, have elevated stability compared to other species, and they fit into the pores of Na-X zeolite. Electronic energy spectra of these clusters have been calculated and compared with experimentally measured ones.

In Situ Synthesis of Robust Polyvinylpyrrolidone-Based Perovskite Nanocrystal Powders by the Fiber-Spinning Chemistry Method and Their Versatile 3D Printing Patterns

All-inorganic halide perovskite nanocrystals (PNCs) have received increasing attention due to their excellent optical properties. However, the inherent instability and the large amount of volatile organic compounds during the production process have severely limited their applications. In this research, we employed the microfluidic electrostatic spinning method to synthesize polyvinylpyrrolidone (PVP)-based PNC (CsPbBr₃/PVP) powders directly by spinning chemistry, where the fibers serve as reactors. Thus, 20.1 g of CsPbBr₃/PVP powders was obtained, which exhibits good fluorescent properties and high stability. Based on these excellent properties, several new applications were explored, including 3D printing, direct encapsulants for light-emitting diodes, and fluorescent coatings. It should be noted that the powder showed distinct advantages in 3D printing, allowing the fabrication of a series of fluorescent patterns, which offers a new candidate for fluorescent 3D printable materials. This work not only opens up an optimal way for facile production of fluorescent powders by the spinning chemistry strategy, but also provides a new perspective for various application directions, especially for 3D printing.

Strong Self-Trapped Exciton Emissions in Two-Dimensional Na-In Halide Perovskites Triggered by Antimony Doping

Soft lattice and strong exciton-phonon coupling have been demonstrated in layered double perovskites (LDPs) recently; therefore, LDPs represents a promising class of compounds as excellent self-trapped exciton (STE) emitters for applications in solid-state lighting. However, few LDPs with outstanding STE emissions have been discovered, and their optoelectronic properties are still unclear. Based on the three-dimensional (3D) Cs₂ NaInCl₆ , we synthesized two 2D derivatives (PEA)₄ NaInCl₈ :Sb (PEA=phenethylamine) and (PEA)₂ CsNaInCl₇ :Sb with monolayer and bilayer inorganic sheets by a combination of dimensional reduction and Sb-doping. Bright broadband emissions were obtained for the first time under ambient temperature and pressure, with photoluminescence quantum efficiency (PLQE) of 48.7 % (monolayer) and 29.3 % (bilayer), superior to current known LDPs. Spectroscopic characterizations and first-principles calculations of excited state indicate the broadband emissions originate from STEs trapped at the introduced [SbCl₆ ]^3- octahedron.

Electron transfers in graphitized HZSM-5 zeolites

In the present work, we report the electron transfers occurring after ionization of the guest molecules of t-stilbene incorporated in graphitized HZSM-5 zeolites and we compare these results with the data obtained previously for graphite-free zeolites. Complementary diffuse reflectance UV-vis and Raman scattering spectroscopies provide evidence for stabilization of long lived charge separated states as observed in non-graphitized ZSM-5. The spectral features indicate that these species are located in the channels of the zeolite structure. However, the pulsed EPR technique shows strong coupling between unpaired electrons and the 13C atoms in the case of graphitized zeolites while this interaction is not observed in normal zeolites. This is assigned to the presence of charge transfer complexes in the close vicinity of graphite areas and to the possible electron transfer to the graphitized domain. Using cyclic voltammetry, an electrochemical response is observed for the first time in such systems demonstrating the role played by graphite in the electron transfers.

Enormous passivation effects of a surrounding zeolitic framework on Pt clusters for the catalytic dehydrogenation of propane

The significant passivation effect of the zeolitic framework on the catalytic performance of Pt clusters for dehydrogenation of propane to propylene is displayed. Pt/NaX shows 1100% enhanced TOFs and largely improved selectivity compared with Pt@NaX.