Nano Ball-Milling Using Titania Nanoparticles to Anchor Cesium Lead Bromine Nanocrystals and Energy Transfer Characteristics in TiO2 @CsPbBr3 Architecture

Continuous-flow synthesis of CsPbI3/TiO2 nanocomposites with enhanced water and thermal stability

The inherent poor stability of CsPbI3 nanocrystals hinders the practical application of this material. Therefore, it is still a challenge to improve the stability of CsPbI3 nanocrystals and realize their large-scale continuous preparation. In this work, we report the preparation of CsPbI3/TiO2 nanocomposites with high stability by a microfluidic method. After the combination of CsPbI3 nanorods with TiO2, the PL intensity increased by 1.3 times under excitation at 577 nm due to the passivating effect of TiO2 on the surface of CsPbI3 nanorods and its carrier transport characteristics. Meanwhile, due to the coating of TiO2, the surface exposure area of CsPbI3 nanorods is reduced, which blocks external environmental effects to some extent and effectively improves the stability of CsPbI3 nanorods. Finally, an LED with a color gamut of 142% NTSC and a color temperature (CCT) of 3952 K was obtained by combining CsPbI1.5Br1.5/TiO2 and CsPbBr3/TiO2 nanocomposites with a blue light chip (455 nm). This study shows that the continuous and controllable synthesis of all inorganic halide perovskite nanocrystals by a microfluidic method is of great significance in the fabrication of high-performance optoelectronic materials and display devices.

Polymer-Surface-Mediated Mechanochemical Reaction for Rapid and Scalable Manufacture of Perovskite QD Phosphors

Perovskite quantum dots (QDs) have been considered new-generation emitters for lighting and displays due to their high photoluminescence (PL) efficiency, and pure color. However, their commercialization process is currently hindered by the challenge of mass production in a quick and environmentally friendly manner. In this study, a polymer-surface-mediated mechanochemical reaction (PMR) is proposed to prepare perovskite QDs using a high-speed multifunction grinder for the first time. PMR possesses two distinctive features: i) The ultra-high rotating speed (>15 000 rpm) of the grinder facilitates the rapid conversion of the precursor to perovskite; ii) The surface-rich polymer particulate ensures QDs with high dispersity, avoiding QD aggregation-induced PL quenching. Therefore, PMR can successfully manufacture green perovskite QDs with a high PL quantum yield (PLQY) exceeding 90% in a highly material- (100% yield), time- (1 kg min-1), and effort- (solvent-free) efficient manner. Moreover, the PMR demonstrates remarkable versatility, including synthesizing by various polymers and producing diverse colored and Pb-free phosphors. Importantly, these phosphors featuring a combination of polymer and perovskite, are facilely processed into various solid emitters. The proposed rapid, green, and scalable approach has great potential to accelerate the commercialization of perovskite QDs.

Remarkable emission enhancement of CsPbBr3 quantum dots based on an Ag nanoparticle-Ag film plasmonic coupling structure

All-inorganic halide perovskite quantum dots (QDs) have recently received much attention due to their excellent optoelectronic properties. And their emission properties still need to be improved for further applications. Here, we demonstrated a remarkable emission enhancement of the CsPbBr3 QDs based on an Ag nanoparticle-Ag film plasmonic coupling structure. Through precise control of the gap distance between Ag nanoparticle and Ag film, the localized surface plasmon resonance (LSPR) peak was tuned to match the emission wavelength of the CsPbBr3 QDs. We achieved a 30-fold fluorescence intensity enhancement and a lower lasing threshold, which is 25% of that of the CsPbBr3 QDs without plasmonic coupling structure. It is attributed to that the plasmonic coupling structure exhibits an extremely strong local electric field owing to the coupling between LSPR of Ag nanoparticle and surface plasmon polariton of Ag film. This work provides an effective way to enhance the optical emission of perovskite QDs and promotes the further exploration of on-chip light source.

All-inorganic lead halide perovskites for photocatalysis: a review

Nowadays, environmental pollution and the energy crisis are two significant concerns in the world, and photocatalysis is seen as a key solution to these issues. All-inorganic lead halide perovskites have been extensively utilized in photocatalysis and have become one of the most promising materials in recent years. The superior performance of all-inorganic lead halide perovskites distinguish them from other photocatalysts. Since pure lead halide perovskites typically have shortcomings, such as low stability, poor active sites, and ineffective carrier extraction, that restrict their use in photocatalytic reactions, it is crucial to enhance their photocatalytic activity and stability. Huge progress has been made to deal with these critical issues to enhance the effects of all-inorganic lead halide perovskites as efficient photocatalysts in a wide range of applications. In this manuscript, the synthesis methods of all-inorganic lead halide perovskites are discussed, and promising strategies are proposed for superior photocatalytic performance. Moreover, the research progress of photocatalysis applications are summarized; finally, the issues of all-inorganic lead halide perovskite photocatalytic materials at the current state and future research directions are also analyzed and discussed. We hope that this manuscript will provide novel insights to researchers to further promote the research on photocatalysis based on all-inorganic lead halide perovskites.

Ultrahigh Stability of Perovskite Nanocrystals by Using Semiconducting Molecular Species for Displays

The instability of perovskite nanocrystals (NCs) to moisture, heat, and blue light severely hinders their commercial applications in quantum dot displays. Here, organic semiconducting molecules are introduced onto CsPbBr₃ NCs, and the as-obtained CsPbBr₃ NCs have a high photoluminescent quantum yield (PLQY) of 82% and extremely high stability in harsh commercial accelerated operational stability tests (such as high temperature (85 °C) and high humidity (85%)). The products can survive and maintain more than 80% of the initial PL intensity value under high temperature, high humidity, and long-term blue light irradiation for hundreds to thousands of hours. They are among the most stable perovskite NCs and even superior to those encapsulated by inert shells and commercial green-emissive CdSe@ZnS quantum dots (QDs). The mechanism of the exceptional stability has been proposed, mainly including the strong interaction and moderate photocarrier transfer between the quasi type II heterostructure formed by the molecule and CsPbBr₃. By using these stable CsPbBr₃ NCs, a QD-enhanced liquid crystal display prototype has been successfully fabricated with a wide color gamut. This work provides understandings on the functionality of ligands in perovskite fields and a promising prospect in perovskite-based display technologies.

Facile Uniaxial Electrospinning Strategy To Embed CsPbBr3 Nanocrystals with Enhanced Water/Thermal Stabilities for Reversible Fluorescence Switches

All-inorganic halide perovskite nanocrystals with their fascinating optical properties have drawn increasing attention as promising nanoemitters. However, due to the intrinsic poor colloidal stability against the external environment, the practical applications are greatly limited. Herein, a facile and effective strategy for the in situ encapsulation of CsPbBr₃ NCs into highly dense multichannel polyacrylonitrile (PAN) nanofibers via a uniaxial electrospinning strategy is presented. Such a facile uniaxial electrospinning strategy enables the in situ formation of CsPbBr₃ NCs in PAN nanofibers without the introduction of stabilizers. Significantly, the obtained CsPbBr₃ nanofibers not only display intense fluorescence with a high quantum yield (≈48%) but also present high stability when exposed to water and air owing to the peripheral protecting matrix of PAN. After immersing CsPbBr₃@PAN nanofiber films in water for 100 days, the quantum yield of CsPbBr₃@PAN nanofibers maintained 87.5% of the original value, which was much higher than that using CsPbBr₃ NCs. Furthermore, based on the spectral overlap between the electrochromic material of ruthenium purple and fluorescence of CsPbBr₃@PAN nanofiber films with excellent water stability, a reversible fluorescence switch is constructed with good fatigue resistance, suggesting their promising applications.

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.

Visible-light driven boosting electron-hole separation in CsPbBr3 QDs@2D Cu-TCPP heterojunction and the efficient photoreduction of CO2

CsPbBr₃ quantum dots (CPB QDs) have great potential in photoreduction of CO₂ to chemical fuels. However, the low charge transportation efficiency and chemical instability of CPB QDs presents a considerable challenge. Herein, we describe the electrostatic assemblies of negatively charged colloidal two dimensional (2D) Cu-Tetrakis(4-carboxyphenyl) porphyrins (Cu-TCPP) nanosheets and positively CPB QDs to construct the hydride heterojunction. The photogenerated electron migration from CPB QDs to Cu-TCPP nanosheets has been witnessed, providing the supply of long-lived electrons for the reduction of CO₂ molecules adsorbed on Cu-TCPP matrix. As a direct result, The CPB@Cu-TCPP-x (x wt% of CPB QDs) photocatalysts exhibit significantly enhanced photocatalytic conversion of CO₂, compared to the parent Cu-TCPP nanosheets or single CPB QDs. Especially, when with 20% CPB QDs, the heterostruture system achieves an evolution yield of 287.08 µmol g^-1 in 4 h with highly CO selectivity (99%) under visible light irradiation, which is equivalent to a 3.87-fold improvement compared to the pristine CPB QDs. Meanwhile, the CH₄ generation rate can be up to 3.25 µmol g^-1. This optimized construction of heterostructure could provide a platform to funnel photoinduced electrons to the reaction center, which can both act as a crucial capture and the reaction actives of CO₂.

Large-scale continuous preparation of highly stable α-CsPbI3/m-SiO2 nanocomposites by a microfluidics reactor for solid state lighting application

CsPbI3-Mesoporous SiO2 nanocomposites with ultrahigh chemical stability were fabricated by the microfluidic technology for large-scale continuous production.

Mechanochemical syntheses of all-inorganic iodide perovskites from layered cesium titanate and bismuth (and antimony) iodide

All-inorganic iodide perovskites were prepared by a mechanochemical reaction between a layered cesium titanate and bismuth (or antimony) triiodide under ambient conditions. The layered cesium titanate was a sacrificial template and also acted as a milling media for the formation of the perovskite nanoparticles with the size of a few nanometres.

Thermal and photo stability of all inorganic lead halide perovskite nanocrystals

Inorganic lead halide perovskite (ILHP) nanocrystals (NCs) show great potential in solid state lighting and next generation display technology due to their excellent optical properties. However, almost all ILHP NCs are still facing the problem of unstable luminescence properties caused by heating and/or UV illumination. Further improving the thermal and photo stability of ILHP NCs has become the most urgent challenge for their practical application. This Perspective review specifically focuses on the thermal and photo stability of ILHP NCs, discusses and analyzes the factors that affect the thermal and photo stability of ILHP NCs from the perspective of surface ligands and structure composition, summarizes the current strategies to improve the thermal and photo stability of ILHP NCs, and presents the key challenges and perspectives on the research for the improvement of thermal and photo stability of ILHP NCs.

Trioctylphosphine-Assisted Pre-protection Low-Temperature Solvothermal Synthesis of Highly Stable CsPbBr3/TiO2 Nanocomposites

Lead halide perovskite quantum dots (PQDs) are reported as a promising branch of perovskites, which have recently emerged as a field in luminescent materials research. However, before the practical applications of PQDs can be realized, the problem of poor stability has not yet been solved. Herein, we propose a trioctylphosphine (TOP)-assisted pre-protection low-temperature solvothermal synthesis of highly stable CsPbBr₃/TiO₂ nanocomposites. Due to the protection of branched ligands and the lower temperature of shell formation, these TOP-modified CsPbBr₃ PQDs are successfully incorporated into a TiO₂ monolith without a loss of fluorescence intensity. Because the excellent nature of both parent materials is preserved in CsPbBr₃/TiO₂ nanocomposites, it is found that the as-prepared CsPbBr₃/TiO₂ nanocomposites not only display excellent photocatalytic activity but also yield improved PL stability, enabling us to build highly stable white light-emitting diodes and to photodegrade rhodamine B.