Ultrathin, Core-Shell Structured SiO2 Coated Mn2+ -Doped Perovskite Quantum Dots for Bright White Light-Emitting Diodes

Damage-Free Silica Coating for Colloidal Nanocrystals Through a Proactively Water-Generating Amidation Reaction at High Temperature

Silica is a promising shell coating material for colloidal nanoparticles due to its excellent chemical inertness and optical transparency. To encapsulate high-quality colloidal nanocrystals with silica shells, the silane coupling hydrolysis is currently the most effective approach. However, this reaction requires water, which often adversely affects the intrinsic physicochemical properties of nanocrystals. Achieving a damage-free silica encapsulation process to nanocrystals by hydrolysis is a huge challenge. Here, a novel strategy is developed to coat colloidal nanocrystals with a denser silica shell via a proactively water-generating reaction at high temperature. In this work, water molecules are continuously and proactively released into the reaction system through the amidation reaction, followed by in situ hydrolysis of silane, completely avoiding the impacts of water on nanocrystals during the silica coating process. In this work, water sensitive perovskite nanocrystals (CsPbBr3 ) are selected as the typical colloidal nanocrystals for silica coating. Notably, this high-temperature in situ encapsulation technology greatly improves the optical properties of nanocrystals, and the silica shells exhibit a denser structure, providing nanocrystals with better protection. This method overcomes the challenge of the influence of water on nanocrystals during the hydrolysis process, and provides an important reference for the non-destructive encapsulation of colloidal nanocrystals.

Biocompatible Silica-Coated Europium-Doped CsPbBr3 Nanoparticles with Luminescence in Water for Zebrafish Bioimaging

Cesium lead halide (CsPbX3 , X = Br, Cl, and I) nanocrystals (NCs) are widely concerned and applied in many fields due to the excellent photoelectric performance. However, the toxicity of Pb and the loss of luminescence in water limit its application in vivo. A stable perovskite nanomaterial with good bioimaging properties is developed by incorporating europium (Eu) in CsPbX3 NCs followed with the surface coating of silica (SiO2 ) shell (CsPbX3 :Eu@SiO2 ). Through the surface coating of SiO2 , the luminescence stability of CsPbBr3 in water is improved and the leakage of Pb2+ is significantly reduced. In particular, Eu doping inhibits the photoluminescence quantum yield reduction of CsPbBr3 caused by SiO2 coating, and further reduces the release of Pb2+ . CsPbBr3 :Eu@SiO2 nanoparticles (NPs) show efficient luminescence in water and good biocompatibility to achieve cell imaging. More importantly, CsPb(ClBr)3 :Eu@SiO2 NPs are obtained by adjusting the halogen components, and green light and blue light are realized in zebrafish imaging, showing good imaging effect and biosafety. The work provides a strategy for advanced perovskite nanomaterials toward biological practical application.

Improving the stability of perovskite nanocrystals via SiO2 coating and their applications

Lead halide perovskite nanocrystals (LHP NCs) with outstanding optical properties have been regarded as promising alternatives to traditional phosphors for lighting and next-generation display technology. However, the practical applications of LHP NCs are seriously hindered by their poor stability upon exposure to moisture, oxygen, light, and heat. Hence, various strategies have been proposed to solve this issue. In this review, we have focused our attention on improving the stability of LHP NCs via SiO2 coating because it has the advantages of simple operation, less toxicity, and easy repetition. SiO2 coating is classified into four types: (a) in situ hydrolytic coating, (b) mesoporous silica loading, (c) mediated anchoring, and (d) double coating. The potential applications of SiO2-coated LHP NCs in the field of optoelectronics, biology, and catalysis are presented to elucidate the reliability and availability of SiO2 coating. Finally, the future development and challenges in the preparation of SiO2-coated LHP NCs are analyzed in order to promote the commercialization process of LHP NC-related commodities.

Recent Advances and Perspectives of Metal Halide Perovskite Heteronanocrystals

Heteronanocrystals that combine multiple semiconductors into a nanoscale heterostructure possess excellent optical performance and flexibility in property engineering compared with their single-component counterparts. The successes in fabricating lead halide perovskite-based heteronanocrystals (PHNCs) have drastically improved the stability and tunability of the optical and electrical properties. However, the epitaxial growth of semiconductor materials on perovskite nanocrystals remains a fundamental challenge because of the mismatch in their surface structure and crystal growth kinetics. Here, we review recent progress in the development of PHNCs with emphasis on their synthesis methods and surface chemistry that led to new insights and reaction protocols for the design and fabrication of PHNCs. In addition, the optical features of different types of PHNCs and nanocomposites and their application perspectives are summarized. Finally, we conclude with a discussion of the remaining issues, challenges, and opportunities in epitaxial growth of Janus and core-shell structure PHNCs.

Application of a Perovskite NIR-LED with Highly Stable FAPbI3@SiO2 Core-Shell Nanocomposites in a SPR Sensing Platform

In recent years, the demand for detection and diagnostic methods has consistently risen due to the aging of the population and the increase in the number of patients with chronic diseases. Label-free biomedical detection techniques have emerged as indispensable instruments for diagnosing a variety of diseases. The development of label-free and highly sensitive near-infrared (NIR) biomedical detection technology has attracted considerable attention. As a label-free, swift, and cost-effective analytical technique, it has demonstrated immense potential for a wide range of applications. We successfully assembled FAPbI3 near-infrared perovskite quantum dots (NIPQDs) into SiO2 shells using a rapid room-temperature atmospheric synthesis method, obtaining monodisperse FAPbI3@SiO2 nanocomposites (NCs) with a high photoluminescence quantum yield (PLQY) of 72%. Additionally, the incorporation of hydrophobic multi-branched trioctylphosphine oxide effectively passivated the surface defects of FAPbI3 NIPQDs and suppressed the hydrolysis rate of tetraethoxysilane, enabling the formation of a highly stable and high PLQY nanoscale-particle level within the FAPbI3@SiO2 core-shell structure. Notably, we successfully incorporated FAPbI3@SiO2 core-shell NCs onto InGaN blue chip as NIR excitation light sources for surface plasmon resonance sensing platforms, providing a novel platform for bioanalytical detection. With a detection sensitivity of 6302.5 nm/RIU, the system demonstrated high sensitivity, stability, and dependability. This achievement expands the biomedical research field's capacity for diagnosis, monitoring, and treatment.

Impact of core-shell perovskite nanocrystals for LED applications: successes, challenges, and prospects

Perovskite nanocrystals (PeNCs) synthesized by colloidal solution methods are an outstanding case of study due to their remarkable optical features, different from their bulk counterpart, such as a tuneable band gap and narrower photoluminescence emission, altered by the size and shape. However, the stability of these systems needs to be improved to consolidate their application in optoelectronic devices. Improved PeNC quality is associated with a less defective structure, as it affects negatively the photoluminescence quantum yield (PLQY), due to the essential, but at the same time labile interaction between the colloidal capping ligands and the perovskite core. In this sense, it would be extremely effective to obtain an alternative method to stabilize the PeNC phases and passivate the surface, in order to improve both stability and optical properties. This objective can be reached exploiting the structural benefits of the interaction between the perovskite and other organic or inorganic materials with a compatible structure and optical properties and limiting the optical drawbacks. This perspective contemplates different combinations of core/shell PeNCs and the critical steps during the synthesis, including drawbacks and challenges based on their optical properties. Additionally, it provides insights for future light emitting diode (LED) applications and advanced characterization. Finally, the existing challenges and opportunities for core/shell PeNCs are discussed.

Mitigating halide ion migration by resurfacing lead halide perovskite nanocrystals for stable light-emitting diodes

Lead halide perovskite nanocrystals are promising for next-generation high-definition displays, especially in light of their tunable bandgaps, high color purities, and high carrier mobility. Within the past few years, the external quantum efficiency of perovskite nanocrystal-based light-emitting diodes has progressed rapidly, reaching the standard for commercial applications. However, the low operational stability of these perovskite nanocrystal-based light-emitting diodes remains a crucial issue for their industrial development. Recent experimental evidence indicates that the migration of ionic species is the primary factor giving rise to the performance degradation of perovskite nanocrystal-based light-emitting diodes, and ion migration is closely related to the defects on the surface of perovskite nanocrystals and at the grain boundaries of their thin films. In this review, we focus on the central idea of surface reconstruction of perovskite nanocrystals, discuss the influence of surface defects on halide ion migration, and summarize recent advances in resurfacing perovskite nanocrystal strategies toward mitigating halide ion migration to improve the stability of the as-fabricated light-emitting diode devices. From the perspective of perovskite nanocrystal resurfacing, we set out a promising research direction for improving both the spectral and operational stability of perovskite nanocrystal-based light-emitting diodes.

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.

Intelligent Colorimetric Indicators for Quality Monitoring and Multilevel Anticounterfeiting with Kinetics-Tunable Fluorescence

The spoilage and forgery of perishable products such as food, drugs, and vaccines cause serious health hazards and economic loss every year. Developing highly efficient and convenient time-temperature indicators (TTIs) to realize quality monitoring and anticounterfeiting simultaneously is urgent but remains a challenge. To this end, a kind of colorimetric fluorescent TTI, based on CsPbBr₃@SiO₂ nanoparticles with tunable quenching kinetics, is developed. The kinetics rate of the CsPbBr₃-based TTIs is easily regulated by adjusting temperature, concentration of the nanoparticles, and addition of salts, stemming from the cation exchange effect, common-ion effect, and structural damage by water. Typically, when combined with europium complexes, the developed TTIs show an irreversible dynamic change in fluorescent colors from green to red upon increasing temperature and time. Furthermore, a locking encryption system with multiple logics is also realized by combining TTIs with different kinetics. The correct information only appears at specific ranges of time and temperature under UV light and is irreversibly self-erased afterward. The simple and low-cost composition and the ingenious design of kinetics-tunable fluorescence in this work stimulate more insights and inspiration toward intelligent TTIs, especially for high-security anticounterfeiting and quality monitoring, which is really conducive to ensuring food and medicine safety.

In situ growth of lead-free halide perovskites into SiO2 sub-microcapsules toward water-stable photocatalytic CO2 reduction

Halide perovskites (HPs) are highly susceptible to heat, light, or moisture and are easily decomposed even in an ambient environment, which greatly hinders their practical applications. Herein, an in situ growth strategy is presented for implanting an inorganic lead-free HP, Cs₂AgBiBr₆, into SiO₂ sub-microcapsules to form a Cs₂AgBiBr₆@SiO₂ yolk-shell composite. The SiO₂ sub-microcapsule endows Cs₂AgBiBr₆ with good thermal and light stability, as well as excellent corrosion resistance against polar solvents. Furthermore, when employed as a lead-free perovskite photocatalyst, the composite exhibits a higher visible-light-driven CO₂-to-CO rate (271.76 μmol g^-1 h^-1) and much better stability than Cs₂AgBiBr₆ in water. The formation of a Cs₂AgBiBr₆/SiO₂ heterostructure using an in situ growth method alleviates water binding on the perovskites, supported by density functional theory calculations, which is the key to an improvement in the stability of the composite. The in situ growth strategy developed here sheds light on the design and development of HP-based materials for applications involving polar solvents.

High-Reliability Perovskite Quantum Dots Using Atomic Layer Deposition Passivation for Novel Photonic Applications

In this study, we propose highly stable perovskite quantum dots (PQDs) coated with Al₂O₃ using atomic layer deposition (ALD) passivation technology. This passivation layer effectively protects the QDs from moisture infiltration and oxidation as well as from high temperatures and any changes in the material characteristics. They exhibit excellent wavelength stability and reliability in terms of current variation tests, long-term light aging tests, and temperature/humidity tests (60°/90%). A white-light system has been fabricated by integrating a micro-LED and red phosphor exhibiting a high data transmission rate of 1 Gbit/s. These results suggest that PeQDs treated with ALD passivation protection offer promising prospects in full-color micro-displays and high-speed visible-light communication (VLC) applications.

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.

Progress of Backlight Devices: Emergence of Halide Perovskite Quantum Dots/Nanomaterials

The technology behind the display is becoming ever more prevalent in our daily lives. It has many applications, including smartphones, tablets, desktop monitors, TVs, and augmented reality/virtual reality devices. The display technology has progressed drastically over the past decade, from the bulky cathode ray tube to the flat panel displays. In the flat panel displays, the liquid crystal display (LCD) and organic light-emitting diodes (OLEDs) are the two dominant technologies. Nevertheless, due to low stability and color tunability, OLEDs remain behind the LCDs. The LCD screen has a backlight, usually a white LED, which comprises a blue LED covered with a red and green enhanced layer (color-converting layers). Although InP/CdSe QDs attracted more attention due to their solution processability and better color gamut than the previous technologies, the complexity of their synthesis was still an obstacle to their commercialization. Later, the emergence of perovskite with highly intense and tunable PL emission, high color purity, and low-cost synthesis route attracted the attention of display researchers. Owing to the relatively higher performance of perovskite quantum dots (PQDs) than that of bulk (3D) perovskite in backlit display devices, these PQDs are being used for high color contrast and bright display devices. Furthermore, the color gamut for PQDs was observed as 140% of the NTSC standard, that is, close to that of the commercial OLED devices. In this review, we have discussed the progress of display technologies with a clear classification of the pros and cons of each technology. Also, the application of perovskite QD/nanomaterials in LCD backlit devices has been discussed, and the future direction of further improvement in their stability and performance has been listed.

Experimental and theoretical study of europium-doped organometal halide perovskite nanoplatelets for UV photodetection with high responsivity and fast response

Herein, we investigate the role of Eu³⁺ doping on CH₃NH₃PbBr₃ nanoplatelets (NPLs) in terms of their optoelectronic properties and photodetection application through a combined experimental and theoretical approach. The introduction of EuCl₃ in the CH₃NH₃PbBr₃ crystal structure by a facile solvothermal method enabled the tuning of the lateral and vertical dimensions of the NSs to form large-area NPLs and finally monolayer nanocrystals. The appearance of low-angle diffraction peaks with Eu doping, which are observed in layered perovskite structures, confirms the formation of quasi-2D NPLs. The bandgap of the Eu-doped mixed halide perovskite systematically increases from 2.39 eV to 2.94 eV with increasing doping concentration. Interestingly, 10 mol% EuCl₃ doping in the pure CH₃NH₃PbBr₃ crystal dramatically enhances its absorbance and photosensitivity, resulting in high-performance photodetection. Under 405 nm excitation, the CH₃NH₃Pb_0.9Eu_0.1Br_2.7Cl_0.3 photodetector exhibits self-biased behavior with an on/off ratio >10³, which is very significant. The planar device achieves a responsivity as high as 5.29 A W^- and a detectivity of 1.06 × 10¹² Jones under 405 nm with a power density of 0.14 mW cm^-2 at 5 V. In addition, the device exhibits very fast response time with a rise/fall time of 17.5/38.5 μs, which is ∼4 times faster than the pristine CH₃NH₃PbBr₃ counterpart. A linear relationship of photocurrent with light intensity in the CH₃NH₃Pb_0.9Eu_0.1Br_2.7Cl_0.3 photodetector signifies low recombination or charge trapping loss. High-performance photodetection in the Eu-doped device is ascribed to the elimination of trap states and the fast charge transfer process. To obtain better insight into the doped system, DFT analysis of the electronic structure of EuCl₃-doped CH₃NH₃PbBr₃ was performed and the results are fully consistent with the experimental findings. It was revealed that EuCl₃ doping increases the density of states near the conduction band along with a blue shift in the bandgap as compared to that of the pristine perovskite, which in turn increases the built-in potential of the fabricated device, resulting in self-biased photodetection. This work paves the way for deeper understanding of lanthanide doping in perovskites and self-biased photodetection applications of a new family of Eu-doped mixed halide perovskite nanostructures.

Highly Luminescent, Stable, and Red-Emitting CsMgxPb1-xI3 Quantum Dots for Dual-Modal Imaging-Guided Photodynamic Therapy and Photocatalytic Activity

In this study, for the first time, red-emitting CsMg_xPb_1-xI₃ quantum dots (QDs) are prepared by doping with magnesium (Mg) ions via the one-pot microwave pyrolysis technique. The X-ray diffraction and X-ray photoelectron spectroscopy results have confirmed partial substitution of Pb²⁺ by Mg²⁺ inside the CsPbI₃ framework. The as-synthesized CsMg_xPb_1-xI₃ QDs have exhibited excellent morphology, higher quantum yield (upto ∼89%), better photostability and storage stability than undoped CsPbI₃. Next, the bioavailability of as-synthesized hydrophobic CsMg_xPb_1-xI₃ QDs is improved by encapsulating them into gadolinium-conjugated pluronic 127 (PF127-Gd) micelles through hydrophobic interactions (PQD@Gd). The optical properties of perovskite quantum dots (PQDs) and the presence of Gd could endow the PQD@Gd with fluorescence imaging, magnetic resonance imaging (MRI), and phototherapeutic properties. Accordingly, the MRI contrasting effects of PQD@Gd nanoagents are demonstrated by employing T₁ and T₂ studies, which validated that PQD@Gd nanoagents had superior MR contrasting effect with a r₂/r₁ ratio of 1.38. In vitro MRI and fluorescence imaging analyses have shown that the PQD@Gd nanoagents are internalized into the cancer cells via a caveolae-mediated endocytosis pathway. The PQD@Gd nanoagents have exhibited excellent biocompatibility even at concentrations as high as 450 ppm. Interestingly, the as-prepared PQD@Gd nanoagents have efficiently produced cytotoxic reactive oxygen species in the cancer cells under 671 nm laser illumination and thereby induced cell death. Moreover, the PQD@Gd nanoagent also demonstrated excellent photocatalytic activity toward organic pollutants under visible light irradiation. The organic pollutants rhodamine b, methyl orange, and methylene blue were degraded by 92.11, 89.21, and 76.21%, respectively, under 60, 80, and 100 min, respectively, irradiation time. The plausible mechanism for the photocatalytic activity is also elucidated. Overall, this work proposes a novel strategy to enhance the optical properties, stability, and bioapplicability of PQDs. The multifunctional PQD@Gd nanoagents developed in this study could be the potential choice of components not only for cancer therapy due to dual-modal imaging and photodynamic therapeutic properties but also for organic pollutant or bacterial removal due to excellent photocatalytic properties.

Encapsulation of lead halide perovskite nanocrystals (NCs) at the single-particle level: strategies and properties

Lead halide perovskite NCs (APbX₃, A = formamidinium (FA), methylammonium (MA) or Cs; X = Cl, Br, I or their mixture) have attracted unprecedented attention due to their excellent photophysical properties and wide application prospects. However, the inherent ionic structure of APbX₃ NCs makes them very sensitive to external conditions such as water and oxygen, resulting in poor stability. As a feasible strategy, encapsulation is considered to be effective in improving the stability. In this minireview, we focus on single-particle-level coating, which not only can improve the stability but also maintain the nano effect of the original NCs. This review summarizes the fundamental information on APbX₃ NCs and the necessity of single-particle-level coating. Subsequently, a variety of heterostructures at the single-particle level are introduced in detail. Then, their applications are summarized. Moreover, we discuss the challenges and prospects of the single-particle-level heterostructures based on APbX₃ NCs.

Enhanced Photoluminescence of All-Inorganic Manganese Halide Perovskite-Analogue Nanocrystals by Lead Ion Incorporation

Herein, we develop an effective approach for incorporating lead (Pb) ions into manganese (Mn) halide perovskite-analogue nanocrystals (PA NCs) of CsMn(Cl/Br)₃·2H₂O via room-temperature supersaturation recrystallization. Pb²⁺-incorporated Mn-PA NCs exhibit strong orange emission upon UV light illumination, a peak centered at 600 nm assigned to Mn²⁺ transition (⁴T_1g → ⁶A_1g) with a photoluminescence quantum yield (PLQY) of 41.8% compared to the pristine Mn-PA NCs with very weak PL (PLQY = 0.10%). The significant enhancement of PLQY is attributed to the formation of [Mn(Cl/Br)₄(OH)₂]^4--[Pb(Cl/Br)₄(OH)₂]^4--[Mn(Cl/Br)₄(OH)₂]^4- chain network structure, in which Pb²⁺ effectively dilutes the Mn²⁺ concentration to reduce magnetic coupling between Mn²⁺ pairs to relax the spin and parity selection rules. In addition, excited energy can effectively transfer from the [Pb(Cl/Br)₄(OH)₂]^4- unit to Mn²⁺ luminescence centers owing to the low activation energy. Pb²⁺-incorporated PA NCs also exhibit excellent stability. The combined strong PL and high stability make Pb²⁺-incorporated Mn-based PA NCs an excellent candidate for potential optronic applications.

Luminescence enhancement of lead halide perovskite light-emitting diodes with plasmonic metal nanostructures

Metal halide perovskites, as newly emerging light emitters, have been attracting considerable attention on luminescent materials and devices, due to their superior optoelectronic properties and potential practical applications. Recently, perovskite light-emitting diodes (PeLEDs) based on lead halide perovskites (LHPs) have been largely designed and intensively studied in laboratory platforms. However, to satisfy demand and promote their commercialization, it is crucial to improve the efficiency and stability of PeLEDs. Accordingly, the surface-plasmon (SP) effect provides a promising approach to enhance their luminescence, which is realized by incorporating plasmonic metal nanostructures (NSs) into PeLEDs. This review presents a comprehensive overview of the research status and prospect on LHP-based plasmonic PeLEDs together with the corresponding perovskite light-emission films (PeLEFs). Firstly, the recent development of the PeLEDs is briefly introduced. Secondly, the mechanisms and photophysics of the PeLEDs by SP manipulation are simply illustrated and analyzed. Then, the recent progress and achievements on the theoretical and experimental results of SP effect applications in the PeLEDs together with PeLEFs are presented in detail and systematically reviewed. Next, the current challenges and future directions of the PeLEDs are shown and discussed. Finally, a critical summary and outlook of the PeLEDs are summarized and proposed. Our results indicate that this new class of LHP-based plasmonic PeLEDs presents future research fields and demonstrates promising applications in lighting and displays, and further luminescence enhancement in exciton radiation processes and light extraction techniques are a hopeful route to obtain high-performance PeLEDs.

Effect of PbSO4-Oleate Coverage on Cesium Lead Halide Perovskite Quantum Dots to Control Halide Exchange Kinetics

The selective control of halide ion exchange in metal halide perovskite quantum dots (PQDs) plays an important role in determining their band gap and composition. In this study, CsPbX₃ (X = Cl⁻, Br⁻, and I⁻) PQDs were self-assembled with PbSO₄-oleate to form a peapod-like morphology to selectively control halide ion exchange. Considering the distinct absorption and bright luminescence characteristics of these PQDs, in situ UV-Vis. absorption and fluorescence spectroscopies were employed to monitor the time-dependent band gap and compositional changes of the PQDs. We determined that the halide exchange in the capped PQDs is hindered—unlike the rapid anion exchange in noncapped PQDs—by a reduction in the halide exchange kinetic rate depending on the extent of coverage of the PQDs. Thus, we tracked the halide ion exchange kinetics between CsPbBr₃ and CsPbI₃ PQDs, depending on the coverage, using in situ UV-Vis. absorption/photoluminescence spectroscopy. We regulated the halide exchange reaction rate by varying the capping reaction temperature of the PQDs. The capping hindered the halide exchange kinetics and increased the activation energy. These results will enable the development of white LEDs, photovoltaic cells, and photocatalysts with alternative structural designs based on the divalent composition of CsPbX₃ PQDs.

Perovskite Quantum Dots with Ultrahigh Solid-State Photoluminescence Quantum Efficiency, Superior Stability, and Uncompromised Electrical Conductivity

All-inorganic perovskite quantum dots (PQDs), potentially applicable to high-performance display technologies, are facing challenges when the superior luminescence properties with high stability and uncompromised electrical conductivity are combined. Here, by introducing hexylamine sulfate and reducing the reaction rate, we managed to optimize the surface sacrificial coating of CsPbBr₃ QDs. As a result, the colloidal PQDs show a photoluminescence quantum efficiency (PLQE) of 95.8% in solution, and an internal PLQE as high as 97.8% in solid-state films. As far as stability is concerned, the PQDs not only show excellent resistance to polar solvent but also can retain over 84% of the initial PL intensity after continuous heating at 100 °C for 60 min. More importantly, the superior stability is achieved without compromising electrical conductivity. The light-emitting diodes made from these PQDs show a current efficiency of 8.9 cd A^-1 with excellent thermal stability.

State of the Art and Prospects for Halide Perovskite Nanocrystals

Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.

Near-unity blue-orange dual-emitting Mn-doped perovskite nanocrystals with metal alloying for efficient white light-emitting diodes

The tunable dual-color emitting Mn²⁺ doped CsPbCl_3-xBr_x nanocrystals (NCs) with near-unity photoluminescence quantum yield (PL QY) were synthesized through post-treatment of metal bromide at room temperature for fabrication of efficient warm white light-emitting diodes (WLEDs). Especially, the CdBr₂ treated blue-orange emitting Mn doped NCs with various Mn/Pb molar feed ratios exhibit higher PL QY of 97% and longer Mn²⁺ PL lifetime of 0.9 ms. It is surprisingly found that the X-ray diffraction peak at 31.9° is almost not changed with increasing Br composition, meaning formation of metal alloying due to incorporation of amount of divalent cation in NCs. The strong and stable Mn²⁺ PL at temperature ranging from 80 K to 360 K are revealed and the temperature-dependent energy transfer efficiencies in Mn²⁺ doped CsPbCl_1.5Br_1.5 NCs are obtained. The enhancement mechanism of Mn²⁺ PL QY was attributed to improved energy transfer from exciton to Mn²⁺ d-d transition and suppressed defect state density after post-treatment. The efficient warm WLEDs with color rendering index of 90 and luminous efficacy of 92 lm/W at 10 mA were fabricated by combining blue-orange dual-emitting Mn²⁺ doped CsPbCl_3-xBr_x@SiO₂ and green emissive CsPbBr₃@SiO₂ NCs with violet GaN chips.

Synthesis of Chemically Stable Ultrathin SiO2-Coated Core-Shell Perovskite QDs via Modulation of Ligand Binding Energy for All-Solution-Processed Light-Emitting Diodes

Recently, perovskite quantum dots (QDs) have attracted intensive interest due to their outstanding optical properties, but their extremely poor chemical stability hinders the development of the high-performance perovskite QD-based light-emitting diodes (PeLEDs). In this study, chemically stable SiO₂-coated core-shell perovskite QDs are prepared to fabricate all-solution-processed PeLEDs. When the SiO₂ shell thickness increases, the chemical stability of perovskite QDs is dramatically improved, while the charge injection efficiency is significantly decreased, which becomes the biggest obstacle for PeLED applications. Thus, controlling the SiO₂ thickness is essential to obtain core-shell perovskite QDs optimal for PeLEDs in an aspect of chemical and optoelectrical properties. The 3-aminopropyl-triethoxysilane (APTES)/oleylamine (OAm) volume ratio is found to be a critical factor for obtaining an ultrathin SiO₂ shell. Optimization of the APTES/OAm ratio affords A-site-doped CsPbBr₃ QDs with an ultrathin SiO₂ shell (A-CsPbBr₃@SiO₂ QDs) that exhibit longer radiative lifetimes and smaller shallow trap fraction than those without A-site doping, resulting in a higher photoluminescence quantum yield. A-CsPbBr₃@SiO₂ QDs also demonstrate long-term superior chemical stability in polar solvents without loss of optical properties due to passivation by the SiO₂ shell and less defects via A-site doping. Consequently, all-solution-processed PeLED is successfully fabricated under ambient conditions, facilitating perovskite QD utilization in low-cost, large-area, flexible next-generation displays.

A universal synthesis strategy for stable CsPbX3@oxide core-shell nanoparticles through bridging ligands

CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) have shown great potential in various optoelectronic devices due to their excellent photophysical properties. However, the poor stability has severely impeded their practical applications. Much effort has been devoted to the preparation of monodisperse core-shell NCs to improve the stability of CsPbX3 NCs. However, it is still challenging to develop a general method to coat CsPbX3 NCs with oxides at the single-particle level. In this work, we report a simple way to prepare monodisperse CsPbX3@SiO2/Ta2O5/ZrO2 core-shell structure NCs using 3-aminopropyl triethoxysilane (APTES) as a bridging ligand. It has been found that careful control of the hydrolysis and condensation process of oxide precursors is critical for the successful preparation of CsPbX3@oxide core-shell NCs. The stability of CsPbI3 NCs upon attack of water, UV-light irradiation, and heating before and after the oxide shell growth has been investigated, demonstrating the efficient protective effect of oxide shells. This work not only provides a novel and universal approach for coating the individual CsPbX3 nanocrystal with various oxide shells but also paves the way for potential practical applications of CsPbX3 NCs because of the enhanced stability.

Multicolor Output from 2D Hybrid Perovskites with Wide Band Gap: Highly Efficient White Emission, Dual-Color Afterglow, and Switch between Fluorescence and Phosphorescence

Herein, an organic fluorophore termed NLAC is introduced into 2D hybrid perovskites with wide band gap (>3.54 eV) to give a green emission with quantum yield up to 81%. The highly efficient luminescence is ascribed to avoiding the aggregation of NLAC and formation of an inorganic free exciton which is easy to thermally quench. On this basis, a new strategy to generate efficient white emission with afterglow has been proposed by codoping a short-wavelength fluorophore and long-wavelength phosphor into 2D organic-inorganic hybrid perovskites (OIHPs). As a result, a single-component white-light-emitting material PEPC-3N based on NLAC with CIE of (0.33, 0.36) and quantum yield up to 43% can be obtained. Interestingly, PEPC-3N shows a dual-color organic afterglow and excitation-wavelength-dependent emission, consequently forming a switch between green fluorescence and yellow afterglow. This unique performance indicates PEPC-3N has huge potential in afterglow WLEDs and information storage.

Interface Chemical Modification between All-Inorganic Perovskite Nanocrystals and Porous Silica Microspheres for Composite Materials with Improved Emission

In recent years, there has been rapid progress in the development of photonic devices based on lead halide perovskite nanocrystals since they possess a set of unique optical and charge transport properties. However, the main limiting factor for their subsequent application is poor stability against exposure to adverse environmental conditions. In this work, a study of a composite material based on perovskite CsPbBr3 nanocrystals embedded in porous silica microspheres is presented. We developed two different approaches to change the interface between nanocrystals and the surface of the microsphere pores: surface treatment of (i) nanocrystals or (ii) microspheres. The surface modification with tetraethylorthosilicate molecules not only increased stability but also improved the optical responses of the composite material. The position of the emission band remained almost unchanged, but its lifetime increased significantly compared to the initial value. The improvement of the optical performance via surface modification with tetraethylorthosilicate molecules also works for the lead-free Bi-doped Cs2AgInCl6 double perovskite nanocrystals leading to increased stability of their optical responses at ambient conditions. These results clearly demonstrate the advantage of a composite material that can be used in novel photonic devices with improved performance.

Lead-free bright blue light-emitting cesium halide nanocrystals by zinc doping

Cesium lead halide perovskite nanocrystals (NCs) have attracted extensive attention for photoelectric device application due to their excellent optoelectronic properties. However, the toxicity of lead has hindered their commercialization. Consequently, lead free cesium metal halide NCs have been developed, but these materials suffer from low photoluminescence quantum yield (PLQY) and poor stability. Here, a new class of lead-free non-perovskite blue-emitting cesium bromine (CsBr) and cesium iodine (CsI) halide NCs are realized by zinc doping. High PLQYs of 79.05% and 78.95% are achieved by CsBr:Zn and CsI:Zn NCs, respectively, attributed to the improved local structural order and reduced strain between the lattices of the NCs after storing under ambient conditions for 20 to 30 days. Moreover, zinc doped cesium halide NCs show excellent air stability for at least 50 days. Our results for zinc doped cesium halide NCs have shown a new avenue to fabricate lead-free halide NCs for blue lighting and display applications.

Photon management to reduce energy loss in perovskite solar cells

Despite the rapid development of perovskite solar cells (PSCs) over the past few years, the conversion of solar energy into electricity is not efficient enough or cost-competitive yet. The principal energy loss in the conversion of solar energy to electricity fundamentally originates from the non-absorption of low-energy photons ascribed to Shockley-Queisser limits and thermalization losses of high-energy photons. Enhancing the light-harvesting efficiency of the perovskite photoactive layer by developing efficient photo management strategies with functional materials and arrays remains a long-standing challenge. Here, we briefly review the historical research trials and future research trends to overcome the fundamental loss mechanisms in PSCs, including upconversion, downconversion, scattering, tandem/graded structures, texturing, anti-reflection, and luminescent solar concentrators. We will deeply emphasize the availability and analyze the importance of a fine device structure, fluorescence efficiency, material proportion, and integration position for performance improvement. The unique energy level structure arising from the 4fn inner shell configuration of the trivalent rare-earth ions gives multifarious options for efficient light-harvesting by upconversion and downconversion. Tandem or graded PSCs by combining a series of subcells with varying bandgaps seek to rectify the spectral mismatch. Plasmonic nanostructures function as a secondary light source to augment the light-trapping within the perovskite layer and carrier transporting layer, enabling enhanced carrier generation. Texturing the interior using controllable micro/nanoarrays can realize light-matter interactions. Anti-reflective coatings on the top glass cover of the PSCs bring about better transmission and glare reduction. Photon concentration through perovskite-based luminescent solar concentrators offers a path to increase efficiency at reduced cost and plays a role in building-integrated photovoltaics. Distinct from other published reviews, we here systematically and hierarchically present all of the photon management strategies in PSCs by presenting the theoretical possibilities and summarizing the experimental results, expecting to inspire future research in the field of photovoltaics, phototransistors, photoelectrochemical sensors, photocatalysis, and especially light-emitting diodes. We further assess the overall possibilities of the strategies based on ultimate efficiency prospects, material requirements, and developmental outlook.

Strong upconverting and downshifting emission of Mn2+ ions in a Yb,Tm:NaYF4@NaLuF4/Mn:CsPbCl3 core/shell heterostructure towards dual-model anti-counterfeiting

Herein, a Yb,Tm:NaYF₄@NaLuF₄/Mn:CsPbCl₃ quasi-core/shell heterostructure is synthesized with the assistance of silica. The strong upconverting and downshifting emission of Mn²⁺ ions was observed in the nanocomposite with a quasi-core/shell structure. The FRET process further improves the energy utilization efficiency of PQDs for UCNPs, which depends on the quasi-core/shell heterostructure. Considering the dual-model fluorescence emission behavior of Mn²⁺ ions, the stable Yb,Tm:NaYF₄@NaLuF₄/Mn:CsPbCl₃ nanocomposite is used in anti-counterfeiting applications.

Chemical synthesis and optical, structural, and surface characterization of InP-In2O3 quantum dots

InP-In₂O₃ colloidal quantum dots (QDs) synthesized by a single-step chemical method without injection of hot precursors (one-pot) were investigated. Specifically, the effect of the tris(trimethylsilyl)phosphine, P(TMS)₃, precursor concentration on the QDs properties was studied to effectively control the size and shape of the samples with a minimum size dispersion. The effect of the P(TMS)₃ precursor concentration on the optical, structural, chemical surface, and electronic properties of InP-In₂O₃ QDs is discussed. The absorption spectra of InP-In₂O₃ colloids, obtained by both UV-Vis spectrophotometry and photoacoustic spectroscopy, showed a red-shift in the high-energy regime as the concentration of the P(TMS)₃ increased. In addition, these results were used to determine the band-gap energy of the InP-In₂O₃ nanoparticles, which changed between 2.0 and 2.9 eV. This was confirmed by Photoluminescence spectroscopy, where a broad-band emission displayed from 2.0 to 2.9 eV is associated with the excitonic transition of the InP and In₂O₃ QDs. In₂O₃ and InP QDs with diameters ranging approximately from 8 to 10 nm and 6 to 9 nm were respectively found by HR-TEM. The formation of the InP and In₂O₃ phases was confirmed by X-ray Photoelectron Spectroscopy.

Recent advances in nanoscale materials for antibody-based cancer theranostics

The quest for advanced management tools or options of various cancers has been on the rise to efficiently reduce their risks of mortality without the demerits of conventional treatments (e.g., undesirable side effects of the medications on non-target tissues, non-targeted distribution, slow clearance of the administered drugs, and the development of drug resistance over the duration of therapy). In this context, nanomaterials-antibody conjugates can offer numerous advantages in the development of cancer theranostics over conventional delivery systems (e.g., highly specific and enhanced biodistribution of the drug in targeted tissues, prolonged systemic circulation, low toxicity, and minimally invasive molecular imaging). This review comprehensively discusses and evaluates recent advances in the application of nanomaterial-antibody bioconjugates for cancer theranostics for the further advancement in the control of diverse cancerous diseases. Further, discussion is expanded to cover the various challenges and limitations associated with the design and development of nanomaterial-antibody conjugates applicable towards better management of cancer.

Highly luminescent biocompatible CsPbBr3@SiO2 core-shell nanoprobes for bioimaging and drug delivery

The encapsulation of lead halide perovskite nanocrystals (PNCs) with an inert protective layer against moisture and the environment is a promising approach to overcome hinderances for their practical use in optoelectronic and biomedical applications. Herein, a facile method for synthesizing highly luminescent and biocompatible CsPbBr₃@SiO₂ core-shell PNCs with a controlled SiO₂ thickness, which are suitable for both cell imaging and drug delivery, is reported. The synthesized CsPbBr₃@SiO₂ core-shell PNCs exhibit bright green emission at 518 nm upon excitation of 374 nm. Interestingly, a significant increase in the photoluminescence intensity is observed with an increase in the SiO₂ shell thickness, which varies with the increasing reaction time. Cytotoxicity results indicate that the CsPbBr₃@SiO₂ core-shell PNCs are nontoxic, making them suitable for in vitro cell imaging using HeLa cells. Furthermore, doxorubicin physically adsorbed on the surface of CsPbBr₃@SiO₂ core-shell PNCs is efficiently released in cells when the drug-loaded perovskite nanoprobes are injected in the cells, indicating that these core-shell nanoparticles can be used for drug loading and delivery. The results of this study suggest that the CsPbBr₃@SiO₂ core-shell PNCs can pave the way for new biomedical applications and processes.

Nonvolatile Multilevel Photomemory Based on Lead-Free Double Perovskite Cs2AgBiBr6 Nanocrystals Wrapped Within SiO2 as a Charge Trapping Layer

Floating gate transistor photomemory (FGTPM) has been regarded as one of the most prospective nonvolatile photomemory devices because of its compatibility with transistor-based circuits, nondestructive reading, and multilevel storage. Until now, owing to the excellent photoelectric properties, lead-based perovskite nanocrystals (PNCs) have been applied in most of the perovskite-based FGTPM devices and embedded in the polymer matrix as the charge trapping layer. However, the polymer matrix and its solvent would degrade the structure of the PNCs, resulting in the loss of their unique photoresponse ability. In addition, lead-based perovskites have environmental unfriendliness and poor stability. Hence, a novel nonvolatile FGTPM based on oligomeric silica (OS) wrapped lead-free double perovskite Cs₂AgBiBr₆ NCs was demonstrated for the first time. Acting synchronously as the protection layer for the discrete Cs₂AgBiBr₆ NCs and charge tunneling layer for the FGTPM device, the OS layer can achieve controllable thickness by adjusting the process parameters, leading to an adjustment of storage properties with a larger memory window (58 V). Owing to the excellent photoresponse ability of the Cs₂AgBiBr₆@OS composite layer, the FGTPM device exhibited high-performance with repeatable multilevel nonvolatile photomemory and precise photoresponse ability of wavelength/time/power-dependent photoirradiation without extra gate biasing.

Correlation of Photoluminescence and Structural Morphologies at the Individual Nanoparticle Level

Single-particle spectroscopy has demonstrated great potential for analyzing the microscopic behavior of various nanoparticles (NPs). However, high-resolution optical imaging of these materials at the nanoscale is still very challenging. Here, we present an experimental setup that combines high sensitivity of time-correlated single-photon counting (TCSPC) techniques with atomic force microscopy (AFM). This system enables single-photon detection with a time resolution of 120 ps and a spatial resolution of 5 nm. We utilize the setup to investigate the photoluminescence (PL) characteristics of both zero-dimensional (0D) and three-dimensional (3D) perovskite nanocrystals and establish a correlation between the particles’ sizes, their PL blinking, and the lifetime behavior. Our system demonstrates an unprecedented level of information, opening the door to understanding the morphology–luminescence correlation of various nanosystems.

Methanol-induced fast CsBr release results in phase-pure CsPbBr3 perovskite nanoplatelets

Formation of a non-emissive wide bandgap CsPb₂Br₅ component often accompanies the synthesis of CsPbBr₃ perovskites, introducing undesired energy states and impeding the charge transport. Here, we demonstrate that a small amount of a methanol additive can promote the CsBr release rate, facilitating CsPbBr₃ formation and suppressing CsPb₂Br₅ formation. Some of the methanol ionizes into CH₅O⁺ and CH₃O^-, which act as surface ligands and change the crystallization environment, inducing shape evolution from spherical nanocrystals to rectangular nanoplatelets (NPLs), leading to monodispersed and phase-pure 8 unit-cell-thick CsPbBr₃ NPLs. Meanwhile, nonradiative recombination processes are inhibited as a result of NPL surface passivation. Bright CsPbBr₃ NPLs with a photoluminescence quantum yield reaching 90% were employed as emitters for electroluminescent light-emitting devices.

Highly stable Na: CsPb(Br,I)3@Al2O3 nanocomposites prepared by a pre-protection strategy

Among the leading energy materials, metal tri-halide perovskite quantum dots (PQDs) with outstanding optoelectronic properties are at the forefront of current research. However, enormous challenges remain to be addressed, including hazardous components and poor stability, before achieving practical applications of PQDs. Although there are diverse methods to improve the stability of PQDs, it is of central importance to avoid damage during operation. Herein, we develop a pre-protected strategy in which the coating combines the advantages of doping with sodium ions to jointly improve stability. Because the stable Na-rich surface acts as a defence, it protects the PQDs from damage during the coating process; therefore, they retain their initial fluorescence. When employing these Na-rich PQDs as core materials of a coating, the highly fluorescent Na: CsPb(Br,I)3@Al2O3 nanocomposites can maintain good stability even when directly immersed in water or exposed to illumination. Clearly, the combination of these features sheds light on the stabilization and applications of PQDs.

Precise Tuning of the Thickness and Optical Properties of Highly Stable 2D Organometal Halide Perovskite Nanosheets through a Solvothermal Process and Their Applications as a White LED and a Fast Photodetector

Precise control of the thickness of large-area two-dimensional (2D) organometal halide perovskite layers is extremely challenging owing to the inherent instability of the organic component. Herein, a novel, highly reproducible, and facile solvothermal route is reported to synthesize and tailor the thickness and optical band gap of the organic-inorganic halide perovskite nanosheets (NSs). Our study reveals that self-assembly of randomly oriented perovskite nanorods leads to the growth of multilayered perovskite NSs at ∼100 °C, while at higher temperature, large-area few-layer to bilayer 2D NSs (CH₃NH₃PbBr₃) are obtained through lattice expansion and layer separation depending precisely on the temperature. Interestingly, the thickness of the 2D NSs shows a linear dependence on the reaction temperature and thus enables precise tuning of the thickness from 14 layers to 2 layers, giving rise to a systematic increase in the band gap and appearance of excitonic absorption bands. Quantitative analysis of the change in the band gap with thickness revealed a strong quantum confinement effect in the 2D layers. The perovskite 2D NSs exhibit tunable color and a high photoluminescence (PL) quantum yield (QY) up to 84%. Through a careful analysis of the steady-state and time-resolved PL spectra, the origin of the lower PL QY in thinner NSs is traced to surface defects in the 2D layers, for the first time. A white light converter was fabricated using the composition-tuned 2D CH₃NH₃PbBrI₂ NS on a blue light-emitting diode chip. The 2D perovskite photodetector exhibits a stable and very fast rise/fall time (24 μs/103 μs) along with high responsivity and detectivity of ∼1.93 A/W and 1.04 × 10¹² Jones, respectively. Storage, operational, and temperature-dependent stability studies reveal high stability of the 2D perovskite NSs under the ambient condition with high humidity. The reported method is highly promising for the development of large-area stable 2D perovskite layers for various cutting-edge optoelectronic applications.

CH3NH3Br solution as a novel platform for the selective fluorescence detection of Pb2+ ions

The development of a simple fluorescent sensor for detecting the Pb²⁺ heavy metal is fundamentally important. The CH₃NH₃PbBr₃ perovskite material exhibits excellent photoluminescence properties that are related to Pb²⁺. Based on the effects of Pb²⁺ on the luminescent properties of CH₃NH₃PbBr₃, we design a novel platform for the selective fluorescence detection of Pb²⁺ ions. Herein, we use a CH₃NH₃Br solution at a high concentration as the fluorescent probe. Incorporation of PbBr₂ into the CH₃NH₃Br solution results in a rapid chemical reaction to form CH₃NH₃PbBr₃. Hence, the nonfluorescent CH₃NH₃Br material displays a sensitive and selective luminescent response to Pb²⁺ under UV light illumination. Moreover, the reaction between CH₃NH₃Br and PbBr₂ could transform Pb²⁺ into CH₃NH₃PbBr₃, and therefore, CH₃NH₃Br may also be used to extract Pb²⁺ from liquid waste in recycling applications.

Glass stabilized ultra-stable dual-emitting Mn-doped cesium lead halide perovskite quantum dots for cryogenic temperature sensing

Mn-Doped CsPb(Cl/Br)3 quantum dots possess multi-functional optical, electronic and magnetic characteristics. However, they usually suffer from decomposition in air, and Mn2+ dopants will be gradually expelled from the perovskite host due to a radius mismatch between Pb2+ and Mn2+. To solve these crucial issues, the synthesis of glass stabilized Mn-doped quantum dots via an appropriate glass composition design and in situ glass crystallization is reported. Mn2+ dopants act as nucleating agents to promote the nucleation/growth of CsPb(Cl/Br)3 from B-P-Zn-Cs-Pb based oxyhalide glass and partition into the perovskite host to produce dual-color luminescence via efficient exciton-to-dopant energy transfer. Benefitting from the effective protection of robust glass, Mn-doped CsPb(Cl/Br)3 quantum dots exhibit superior water resistance and thermal stability. Particularly, almost 100% luminescence is retained after immersing the composite in water for 30 days. Interestingly, rapid thermal quenching for exciton recombination relative to Mn2+ d-d transition at cryogenic temperatures enables its promising applications as a ratiometric temperature sensing medium.

Improved Doping and Emission Efficiencies of Mn-Doped CsPbCl3 Perovskite Nanocrystals via Nickel Chloride

It is challenging to improve the emission efficiency of Mn-doped CsPbCl₃ (Mn:CsPbCl₃) nanocrystals (NCs) because the excellent optical performances are dependent on high doping efficiency and few defects and traps. Steady-state and time-resolved photoluminescence (PL) spectroscopies were used to investigate the luminescence properties of Mn:CsPbCl₃ NCs with different Mn doping levels synthesized in the presence of nickel chloride. The doping efficiency of Mn ions in Mn:CsPbCl₃ NCs was greatly enhanced in the presence of NiCl₂, and the PL wavelength of Mn²⁺ ions was tuned from 594 to 638 nm by varying the concentration of dopant Mn from 0.11% to 15.25%. The high emission quantum yields of Mn:CsPbCl₃ NCs with orange and red emissions peaked at 600 and 620 nm in hexane were 70% and 39%, respectively. The improvement in doping and emission efficiencies of Mn²⁺ was attributed to the enhanced formation energies of the Mn doping under the Mn and Ni codoped configuration and the resulting reduction of defects and traps in Mn:CsPbCl₃ NCs with incorporation of Ni²⁺ ions.

Improved ultraviolet radiation stability of Mn2+-doped CsPbCl3 nanocrystals via B-site Sn doping

A facile and effective B-site Sn doping strategy is used to grow Mn²⁺-doped CsPbCl₃ (Mn:CsPbCl₃) nanocrystals with enhanced ultraviolet irradiation stability and luminescence properties.