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The instability of halide perovskite nanocrystals (PNCs) and related composite polymer films posed considerable challenges for application in flexible optoelectronic devices. Herein, perovskite nanocrystal‐polymethyltrifluoropropylsiloxane (PNCs‐PMFS) composites are developed that exhibit outstanding optical stability and irradiation resistance through a mutually reinforcing strategy. The photoluminescence (PL) intensity of PNCs‐PMFS remained stable after four heating cycles, whereas perovskite nanocrystal‐polydimethylsiloxane (PNCs‐PDMS) composites exhibited a 31% decrease in PL intensity. Moreover, PNCs‐PMFS demonstrated superior luminescence stability under UV and X‐ray irradiation due to strong ion‐dipole interactions between PNCs and trifluoromethyl (CF3) dipoles. Under γ‐ray irradiation (300 kGy), PNCs‐PMFS retained 73% (2.86 MPa) of the initial mechanical strength, while PMFS without PNCs retained only 51%. This enhancement is attributed to the effective reduction of free radical concentration in the system by PNCs, as confirmed by electron spin resonance (ESR) and curing curve. Density‐functional theory (DFT) calculations further indicated that PNCs adsorbed free radicals, thereby facilitating interfacial charge transfer and forming a stable resonance structure. These advancements enabled PNCs‐PMFS to serve as scintillation screens for X‐ray detection and imaging, achieving a spatial resolution of 19.0 lp mm−1 and a detection limit of 3.78 µGy s−1, offering novel insights for designing of X‐ray detectors in high‐energy radiation environments. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Inorganic lead halide perovskite (LHP) nanostructures, represented by formula CsPbX3 (X = Cl, Br, I), have garnered considerable interest for their exceptional optical properties and diverse applications. Despite their potential, challenges such as environmental degradation persist. In‐situ synthesis within protective materials pores is a promising way to address this issue. However, confining perovskite nanostructures into porous matrices during the synthesis can limit their photoluminescence quantum yield (PL QY) and tunability of optical properties. Various post‐treatment approaches exist to improve the properties of LHP and achieve their desired functionalities, but these strategies have not been explored for LHP confined in mesoporous matrices. Here, we demonstrate the efficacy of in‐situ post‐synthetic treatments to improve the optical properties of CsPbBr3 nanocrystals grown in nanoporous silica microspheres. Surface passivation with Br– ion‐containing precursors boosts PL QY, while anion‐assisted cation doping with Mn2+ ions introduces a new PL band. The adjustment of precursor amount and doping duration enables precise control over the optical properties of LHP, while additional coating with a SiO2 shell enhances their stability in polar solvents, expanding the potential applications of these composites. [ABSTRACT FROM AUTHOR]

Perovskite CsPbBr3 nanocrystals show excellent optical properties. However, the nanocrystals encounter a major challenge of poor stability. In this study, an effective approach is proposed for enhancing the stability of CsPbBr3 nanocrystals via a dual passivation strategy, where the dual passivation layer is composed of alumina (Al2O3) and polymer ethylene‐vinyl acetate (EVA). The Al2O3 coating on the CsPbBr3 surface is realized by in situ oxidation of trimethyl aluminum (TMA), which passivated the surface defects while blocking the intrusion of water and oxygen. The EVA film is formed by a solution method, which can further block the water and oxygen, and form the flexible composite with perovskite CsPbBr3 nanocrystals with enhanced stability toward water and heat. After soaking for 360 h and heating for 5 h, the photoluminescence (PL) intensity is higher than that without passivation. The polymer EVA packaging strategy provided CsPbBr3 with excellent extensibility and flexibility at 100% and 200% tensile rates, the PL intensity remains 91% and 88% of the initial intensity, which returns to the initial value after stretching. The unique dual‐protection structure significantly improves the water and thermal stability of the nanocrystals. The strategy might point out the direction for the future application of perovskites. [ABSTRACT FROM AUTHOR]

The exponential growth of data from sensors and internet‐connected devices has challenged traditional electronic computing, particularly in processing speed and power efficiency. Optical information processing, with its inherent high speed and parallelism, offers a promising solution. Moreover, optical processing is vital for developing all‐optical networks, where all‐optical imaging is essential. In this paper, a novel all‐optical imaging technique that leverages in situ anion exchange reactions between perovskite nanocrystals to create an array of pixels with tunable emission wavelengths is proposed. This method enables the conversion of UV light, whether transmitted or reflected by an object, into the visible spectrum, thereby establishing a direct correlation between spectral and spatial information. By employing wavelength division multiplexing (WDM), the approach reduces the dimensionality of information acquisition from two dimensions to one, enhancing imaging speed. This innovation paves the way for significant advancements in all‐optical imaging and image processing, offering new possibilities for faster and more efficient imaging technologies. [ABSTRACT FROM AUTHOR]

Lead halide perovskite nanocrystals (LHP NCs) are generally prone to surface defect formation during the purification process, resulting in a reduced photoluminescence (PL) quantum yield. The purification of LHP NCs using antisolvents leads to the detachment of surface atoms and ligandsin the form of alkylammonium‐halides or A‐carboxylates (A: Cs, methylammonium, MA, or formamidinium, FA. Currently, intense research is being carried out to improve the surface stability of LHP NCs using various long‐chain organic ligands that strongly bind to the surface of NCs. Herein, the findings on the higher surface stability of hybrid (MAPbBr3 and FAPbBr3) LHP NCs compared to that of inorganic CsPbBr3 NCs against purification with polar antisolvents are reported. It is discovered that the CsPbBr3 NC surface stability can be enhanced (reaching that of hybrid perovskite NCs) by the incorporation of a small amount of MA or FA A‐site organic cations into their lattice, corroborated by the evidence that the PL quantum yield of mixed A‐cation CsxFA1‐xPbBr3 and CsxMA1‐xPbBr3 NCs remains unaffected after several purification cycles. It is hypothesized that this is attributed to hydrogen bonding between the organic A‐site cations and the neighboring halides on the surface. These findings are not only fundamentally important but are also expected to have wide implications in the field of metal‐halide perovskite optoelectronics. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals are sought after for many optical and optoelectronic applications, such as light‐emitting diode and solar cells, due to their outstanding optical properties. However, their ionic nature makes them susceptible to ambient conditions. One rational solution to this challenge is the passivation or encapsulation of perovskite nanocrystals to isolate them from their environments. Thus, there is an urgent need to develop efficient methods for encapsulating emissive perovskite nanocrystals. A facile post‐synthesis method is proposed to treat CsxFA(1−x)PbBr3 nanocrystals, in the presence of Fe3+ cations, to create a robust and water‐stable nanocomposite structure, where 3D CsPbBr3 nanocrystals are embedded in and thus protected by the 2D CsPb2Br5 nanosheets (named as CsPbBr3/CsPb2Br5 hereafter). These Fe3+ cations facilitate the formation of the CsPbBr3/CsPb2Br5 composite and regulate the growth of 2D CsPb2Br5 sheets. By performing controlled experiments, the possible mechanism of 2D nanosheet growth is proposed and discussed in detail. More importantly, the composite can remain stable in water for three months and exhibits amplified spontaneous emission under femtosecond laser irradiation. This work presents a synthesis pathway for producing durable perovskite composites that are promising for future lasing applications. [ABSTRACT FROM AUTHOR]

Post‐synthetic halide anion exchange is considered a “double‐edged sword” for perovskite nanocrystals (PNCs), which offer unique access to color tunability while bringing about surface defects. Herein, a novel surface cation cross‐locking (SCCL) strategy is proposed to achieve the anion‐exchanged CsPbX3 PNCs (X is Cl, Br, I) with non‐destructive emissions. This is achieved using a dendritic ligand of Pentaerythritol tetrakis (3‐mercaptopropionate) (PETMP) as a surface cross‐locker, which can form the multiple coordination to the surface Pb cation of octahedral [PbX6]4− during the fast halide anion exchange via four end‐thiolates and four side‐carboxylates. As a result, the red‐ and blue‐emitting anion‐exchanged CsPbX3 PNCs exhibit high photoluminescence quantum yield (PLQY) values of >97%, close to the parent green‐emitting CsPbBr3 PNCs. Moreover, the “on‐demand” synthesis of anion‐exchanged CsPbX3 PNCs is also performed via autonomous robotic in‐flow experimentation. This work provides a new general post‐synthetic way for the full‐color CsPbX3 PNCs with compositions that are inaccessible via direct synthetic routes. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals are embedded into metal–organic frameworks (MOFs) to create composites with high light absorption coefficients, tunable electronic properties, high specific surface area, and metal atom tunability for enhanced photocatalytic carban dioxide (CO2) reduction. However, existing perovskite‐MOF structures with a large particle size are achieved based on Pb source adsorption into the pores of MOFs, which can significantly break down the porous structure, thereby resulting in a decreased specific surface area and impacting CO2 adsorption. Herein, a novel perovskite‐MOF structure based on the synthesis of bimetallic Pb‐containing MOFs and post‐processing to convert Pb to CsPbBr3 nanocrystals (NCs) is proposed. It is discovered that the additional Pb is not introduced by adsorption, but instead engages in coordination and generates Pb‐N. The produced ZIF‐8@CsPbBr3 NCs are ≈40 nm and have an ultra‐high specific surface area of 1325.08 m2g−1, and excellent photovoltaic characteristics, which are beneficial for photocatalytic CO2 reduction. The electronic conversion rate of composites is 450 mol g−1h−1, which is more than three times that of pure perovskites. Additionally, the superior reduction capacity is sustained after undergoing four cycles. Density Functional Thoery (DFT) simulations are used to explore the 3D charge density at the ZIF‐8@CsPbBr3 NCs interface to better understand the electrical structure. [ABSTRACT FROM AUTHOR]

The exceptional optoelectronic properties of lead halide perovskite nanocrystals (PeNCs) in the ultraviolet and visible spectral regions have positioned them as a promising class of semiconductor materials for diverse optoelectronic and photovoltaic applications. However, their limited response to near‐infrared (NIR) light due to the intrinsic bandgap (>1.5 eV) has hindered their applications in many advanced technologies. To circumvent this limitation, it is of fundamental significance to integrate PeNCs with lanthanide‐doped upconversion nanoparticles (UCNPs) that are capable of efficiently converting low‐energy NIR photons into high‐energy ultraviolet and visible photons. By leveraging the energy transfer from UCNPs to PeNCs, this synergistic combination can not only expand the NIR responsivity range of PeNCs but also introduce novel emission profiles to upconversion luminescence with multi‐dimensional tunability (e.g., wavelength, lifetime, and polarization) under low‐to‐medium power NIR irradiation, which breaks through the inherent restrictions of individual PeNCs and UCNPs and thereby opens up new opportunities for materials and device engineering. In this review, we focus on the latest advancements in the development of PeNCs‐UCNPs nanocomposites, with an emphasis on the controlled synthesis and optical properties design for advanced optoelectronic applications such as full‐spectrum solar cells, NIR photodetectors, and multilevel anticounterfeiting. Some future efforts and prospects toward this active research field are also envisioned. [ABSTRACT FROM AUTHOR]

With their exceptional optoelectronic properties, CsPbBr3 perovskite nanocrystals (NCs) are promising materials for light‐emitting devices. Elucidating their stimulated emission mechanisms is fundamental to grasp the limitations hindering their use as electrically pumped lasers. In particular, two questions remain open: why the Amplified Spontaneous Emission (ASE) band is significantly shifted from the fluorescence one, and why the former seems to suddenly emerge from, and coexist with, the latter. Here, these questions are addressed through experimental ASE measurements, combined with numerical simulations and a comprehensive assessment of the performance of different analytical expressions used in the literature to retrieve the optical gain from these experiments. This multi‐facet study shows that the ASE behavior in CsPbBr3 NCs thin films stems from four distinctive processes: reabsorption due to a large overlap between the absorption and fluorescence spectra, a strong contribution of excited state absorption within the fluorescence window, the excitation of differently polarized waveguide modes, and the coexistence of short‐ and long‐lived localized excitons. The results in this work delineate the best practices to analyze the optical gain in perovskite samples, help to understand their ASE mechanisms, and provide insights to boost their lasing efficiency. [ABSTRACT FROM AUTHOR]

Interfaces between nanocrystals and their stabilizing ligands in light‐harvesting devices are crucial for mediating energy transfer, essential for efficient solar energy conversion. In metal halide perovskites, a promising material for these devices, Förster resonance energy transfer (FRET) within perovskite/acceptor‐molecule complexes offers a pathway for optimized energy transfer. However, traditional methods for optimizing FRET in perovskite‐chromophore hybrids are based on static modifications. This study presents an innovative approach for light‐driven dynamic control of FRET, achieving an ≈14% enhancement in efficiency between CsPbBr3 nanocrystals (CPB NCs) and rhodamine B isothiocyanate (RITC) dye. UV light is utilized to reversibly regulate NC‐ligand binding and thus control the coupling between CPB NCs and RITC at their interface. This approach critically relies on strong NC–ligand interactions, such as the Pb─S bond between CPB NCs and RITC. Light exposure weakens the binding of surface ligands, allowing RITC, with its strong bond, to attach more effectively and promote enhanced energy transfer. This light‐activated control is absent with Rhodamine B (RhB) lacking ─NCS group, a strong binding motif. The findings reveal the importance of NC–ligand interactions in dynamically manipulating FRET with light. This pioneering method for nanoscale FRET control paves the way for more efficient light‐harvesting devices. [ABSTRACT FROM AUTHOR]

Cesium copper halide (CCH) nanocrystals (NCs) have gained significant interest as a Pb-free alternative to conventional cesium lead halide NCs in fabricating LEDs due to their broadband emission. An in-depth analysis of the origin of such broadband emission in colloidal CCH NCs is presented in this work. Further, the effect of introducing Mn as an emission center in CCH by in situ doping facilitates easy energy transfer to analytes exhibiting remarkable picomolar sensitivity (1.86 pM) toward bentazone (analyte) which otherwise was difficult to achieve, even microlevel sensitivity. A mechanism that can predict the success of sensitized dopant emission and guide the design of host–guest combinations has been systematically elucidated. [ABSTRACT FROM AUTHOR]

Colloidal lead halide perovskite nanocrystals (LHP NCs) are promising semiconductor materials for optoelectronic devices, but the high ionicity of LHP NCs makes their crystallization control and post-treatment difficult. Here, phosphonic acids (PAs) are employed as ligands to design a solid-liquid heterogeneous reaction system to regulate the LHP NC crystallization and achieve the desired focusing growth. During the heterogeneous synthesis, the precursors in the liquid phase are responsible for the burst nucleation and initial growth of NCs. Afterwards, the focusing growth of NCs is supported by the precursors released from the solid phase. In addition, the strong binding ability of PAs enables effective passivation of LHP NCs. Without post-treatment, gram-scale monodisperse CsPbBr3 NCs having photoluminescence with a full width at half-maximum of 18 nm and a quantum yield of near-unity are obtained. The CsPbBr3 NCs covered by a compact ligand layer keep initial quantum yield even after 18 cycles of purification, exhibiting excellent stability against polar solvents, ultraviolet irradiation and heat treatment. As scintillators, the prepared CsPbBr3 NCs show strong radioluminescence emission and highresolution X-ray imaging. [ABSTRACT FROM AUTHOR]

The primary challenge facing perovskite nanocrystals (PNCs) is their stability, which hinders their potential impact on the industry. This study focuses on new organic–inorganic metal halide perovskites (OIMHPs) with stable deep blue emission using the beneficial encapsulation aspects of metal–organic frameworks (MOFs). Novel (Et)3NHPbBr3 PNCs with deep blue emission were synthesized via the facile ligand‐assisted reprecipitation (LARP) technique. To address both stability issues and low emission efficiency, the (Et)3NHPbBr3 PNCs were effectively embedded within zinc‐based mesoporous MOF‐5 structures. The pore structure of MOF‐5 microporous (with pores size of 1.68 nm) was initially modified to mesoporous (M3 with pores size of 36.88 nm) to facilitate the localization of PNCs inside MOF pores. Then, a full series of experimental parameters were optimized, which resulted in about 10‐fold enhancement in photoluminescence quantum efficiency (PLQE) from 6% for the bare (Et)3NHPbBr3 PNCs to 58% for the (Et)3NHPbBr3@MOF‐5 composite with emission signal located at around 394 nm. The emission stability of the fabricated composite was also investigated against external conditions and showed that the optimized composite has an excellent emission after 180 days of storage in environmental conditions, along with a preserved PL emission at elevated temperatures up to 100 °C. This study presents a straightforward and cost‐effective method for producing novel deep‐blue emissive (Et)3NHPbBr3 PNCs encapsulated within MOFs, showcasing substantial improvements in PLQE and stability that are crucial for the development of efficient optoelectronic devices. [ABSTRACT FROM AUTHOR]

All inorganic metal halide perovskite nanocrystals (NCs) have attracted much attention for their outstanding optoelectronic properties, which can be tuned by the composition, surface, size and morphology in nanoscale. Herein, we report the microfluidic synthesis of hollow CsPbBr3 perovskite NCs through the nanoscale Kirkendall effect. The formation mechanism of the hollow structure (Kirkendall void) controlled by the temperature, flow rate, ratios of precursors and ligands was investigated. Compared with the solid CsPbBr3 NCs of the same size, the hollow CsPbBr3 NCs exhibit blue shifts in ultraviolet–visible (UV–vis) absorption and photoluminescence (PL) spectra, and remarkably longer PL average lifetime (~ 98.2 ns). Quantum confinement effect, inner surface induced additional trap states and lattice strain of the hollow CsPbBr3 NCs were discussed in understanding their unique optoelectronic properties. The hollow CsPbBr3 NC based photodetector exhibits an outstanding negative photoconductivity (NPC) detectivity of 8.9 × 1012 Jones. They also show potentials in perovskite NC based photovoltaic and light emitting diodes (LEDs). [ABSTRACT FROM AUTHOR]

Cesium lead halide (CsPbX 3 , X = Br, I) perovskite nano-crystals (PNCs) with modified compositions were synthesized within boro-germanate glass ceramics to obtain an efficient red color converter for ultra-high definition (UHD) display application. The glass composition and heat treatment conditions were varied to achieve a high photo-luminescence quantum yield (PLQY) under a blue (450 nm) light emitting diode (LED) excitation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of CsPb(Br/I) 3 PNCs within the glass matrix. A high PLQY of up to 70.5 % was achieved under 450 nm blue LED excitation. The role of composition on the glass structure and PNC formation as well as PL-QY was investigated by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The stability of the CsPb(Br/I) 3 PNC embedded glass (PNEG) against temperature, water, and continuous LED irradiation was examined, and revealed significantly improved photo, chemical and thermal stability compared to colloidal PNCs. Practical feasibility for display applications was demonstrated by fabricating a white LED using the present red PNEG mixed with green CsPbBr 3 PNEG in a remote phosphor-in-silicone structure, showing a wide color gamut of 138.9 % of the NTSC. [ABSTRACT FROM AUTHOR]

Mixed Br/Cl perovskite nanocrystals (PeNCs) exhibit bright pure‐blue emission benefiting for fulfilling the Rec. 2100 standard. However, phase segregation remains a significant challenge that severely affects the stability and emission spectrum of perovskite light‐emitting diodes (PeLEDs). Here, we demonstrate the optimization of the spacing between polydentate functional groups of polymer ligands to match the surface pattern of CsPbBr1.8Cl1.2 PeNCs, resulting in effective synergistic passivation effect and significant improvements in PeLED performances. The block and alternating copolymers with different inter‐functional group spacing are facilely synthesized as ligands for PeNCs. Surprisingly, block copolymers with a higher functional group density do not match PeNCs, while alternating copolymers enable efficient PeNCs with the high photoluminescence intensity, low non‐radiative recombination rate and high exciton binding energy. Density functional theory calculations clearly confirm the almost perfect match between alternating copolymers and PeNCs. Finally, pure‐blue PeLEDs are achieved with the emission at 467 nm and Commission Internationale de l′Eclairage (CIE) coordinates of (0.131, 0.071), high external quantum efficiency (9.1 %) and record spectral and operational stabilities (~80 mins) in mixed‐halide PeLEDs. Overall, this study contributes to designing the polymer ligands and promoting the development of high‐performance and stable pure‐color PeLEDs towards display applications. [ABSTRACT FROM AUTHOR]

Flexible circularly polarized luminescence (CPL) exhibits significant potential for applications in smart wearable devices and high‐end anti‐counterfeiting. However, existing technologies suffer from low dissymmetry factor (glum) and poor mechanical reliability. Here, a metal halide perovskite is employed as the emitter to construct efficient and robust flexible CPL films through a facile strategy of bilayer stacking, which comprises a layer of perovskite nanocrystalline embedded polymer film and a layer of photonic crystal film based on polymerized chiral liquid crystals (LCs). The photoluminescence efficiency of perovskite nanocrystals in polyacrylonitrile (PAN) matrix is improved by incorporating an appropriate amount of phenylethylammonium bromide (PEABr) as a passivation agent, and the helical arrangement and optical activity of free‐standing flexible photonic crystal films are found to be highly related to the supporting substrates. Upon stacking, the resulting flexible composite film exhibits extremely high |glum| values of up to 1.81, representing the highest value among reported flexible CPL‐active films. Moreover, the composite films demonstrate remarkable mechanical robustness, which shows negligible degradation in terms of glum value even after 1000 bending cycles at a bending radius of 2 mm. Based on the flexible CPL‐active films, advanced anti‐counterfeit labels with switchable patterns under circular polarizers are demonstrated. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals (NCs) possess immense potential in photocatalysis. However, deciphering the intricate surface chemistry that governs these catalytic processes remains a challenge. This study investigates C-X bond activation with CsPbBr3 NCs, focusing on elucidating the role of dynamic molecular domains in dictating catalytic activity. By manipulating surface interactions through ligand dynamics, we identify halide vacancies as critical sites for C-X bond activation. A systematic exploration of different ligand types reveals varying kinetics of C-X exchange, with oleyl amine-capped CsPbBr3 NCs demonstrating the highest reactivity. Temperature-dependent photoluminescence measurements corroborate these findings, highlighting the influence of ligand dynamics on surface interactions. Additionally, postsynthetic treatments, such as lead oleate modification, which leads to an increase in the density of active sites (halide vacancies), significantly enhance catalytic performance. Conversely, SOBr2 treatment, which repairs surface bromide vacancies, results in almost completely suppressed catalytic activity. So, by engineering surface environments, we demonstrate significant improvement in the catalytic performance of metal halide perovskite NCs, offering valuable insights for future development. [ABSTRACT FROM AUTHOR]

The ligand engineering of inorganic lead halide perovskite quantum dots (PQDs) is an indispensable strategy to boost their photoluminescence stability, which is pivotal for optoelectronics applications. CsPbX3 (X = Cl, Br, I) PQDs exhibit exceptional optical properties, including high color purity and tunable bandgaps. Despite their promising characteristics, environmental sensitivity poses a challenge to their stability. This article reviews the solution-based synthesis methods with ligand engineering. It introduces the impact of factors like humidity, temperature, and light exposure on PQD's instability, as well as in situ and post-synthesis ligand engineering strategies. The use of various ligands, including X- and L-type ligands, is reviewed for their effectiveness in enhancing stability and luminescence performance. Finally, the significant potential of ligand engineering for the broader application of PQDs in optoelectronic devices is also discussed. [ABSTRACT FROM AUTHOR]

The 5d→4f transition of Ce3+ is allowed by the electric dipole and the parity selection rule and the position/intensity of the 5d excited state is strongly dependent on the materials' composition and atomic structure. Herein, the composition‐dependent luminescence properties of Ce3+ in CsPbCl3‐xBrx (0 ≤ x ≤ 3) perovskite nanocrystals (PeNCs) are systematically revealed. It's observed that the 5d‐4f broadband emission of Ce3+ is greatly improved by optimizing the Cl:Br ratio due to the efficient energy transfer from excitons to Ce3+. Folic acid, a vitamin which is an extremely important cofactor, is introduced to regulate the film formation by interacting with uncoordinated ions. The modified CsPbCl1.5Br1.5 PeNCs with photoluminescence quantum yield of 91% represent a novel and extremely efficient white nanophosphor. Then, white light‐emitting diodes (WLEDs) are constructed by combining Ce3+‐doped PeNCs with 400‐nm ultraviolet chips with a luminous efficiency of 120.3 lm W−1, which is the most efficient perovskite single‐component WLED. Moreover, the blue‐violet LEDs are fabricated with external quantum efficiency of 0.84%, representing extremely high level of 400–435 nm perovskite LEDs. This work demonstrates the strategy in realizing high‐efficiency wavelength‐tunable PeNCs, motivating the further exploration of Ce3+‐doped perovskites in optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this work we successfully synthesize CsPb(Br x I 1-x) 3 perovskite nanocrystals with different Br/I ratio in a borogermanate glass matrix. The XRD studies show cubic perovskite phase peaks shift as the Br/I ratio changes. The formed nanocrystals have mean size of about 17 nm based on the calculations from the absorption spectra. The smooth change of the Br/I ratio in perovskite nanocrystals allow to obtain luminescence in the range 500–750 nm with quantum yield up to 35 %. The luminescence quantum yield and lifetime of the mixed-halide nanocrystals steadily increase with iodine concentration. Practical application of perovskite glass-ceramics as a radiation converter is shown in the paper. [Display omitted] [ABSTRACT FROM AUTHOR]

White light is of great technical interest in many photonic applications. In this work, colloidal solutions containing mutually immiscible green perovskite nanocrystals and red InP quantum dots are developed as color‐conversion (CC) materials for generating white light. By combining the green/red CC materials and a blue top‐emission organic light‐emitting diode as an excitation source, it is possible to generate white light with a range of color temperatures (CTs). The technical approach can be extended to a wide variety of photonic applications where controllable CT is desirable. [ABSTRACT FROM AUTHOR]

In this paper, we present an efficient and rapid method for synthesizing perovskite nanoparticles (PeNPs) using ultrasonic spray techniques. The synthesized PeNPs are notably larger than the exciton Bohr radius of perovskite, avoiding the quantum confinement effect, and exhibit a size distribution of around 61.6 ± 30 nm. They show an exceptionally narrow full width at half-maximum of approximately 21.8 nm and a high exciton binding energy (Eb) of approximately 204 meV. Furthermore, the physically restrained reprecipitation method not only effectively transforms perovskite precursor droplets into solid PeNPs at the interface of an antisolvent but also concurrently achieves ligand passivation. This dual-action mechanism promotes their dispersion in various organic solvents and highly concentrated solutions, thus significantly expanding the scope of potential optoelectronic applications such as light-emitting diodes and photodetectors. [ABSTRACT FROM AUTHOR]

Decreasing perovskite nanocrystal size increases radiative recombination due to the quantum confinement effect, but also increases the Auger recombination rate which leads to carrier imbalance in the emitting layers of electroluminescent devices. Here, we overcome this trade‐off by increasing the exciton effective mass without affecting the size, which is realized through the trace Cd2+ doping of formamidinium lead bromide perovskite nanocrystals. We observe an ~2.7 times increase in the exciton binding energy benefiting from a slight distortion of the [BX6]4− octahedra caused by doping in the case of that the Auger recombination rate is almost unchanged. As a result, bright color‐saturated green emitting perovskite nanocrystals with a photoluminescence quantum yield of 96 % are obtained. Cd2+ doping also shifts up the energy levels of the nanocrystals, relative to the Fermi level so that heavily n‐doped emitters convert into only slightly n‐doped ones; this boosts the charge injection efficiency of the corresponding light‐emitting diodes. The light‐emitting devices based on those nanocrystals reached a high external quantum efficiency of 29.4 % corresponding to a current efficiency of 123 cd A−1, and showed dramatically improved device lifetime, with a narrow bandwidth of 22 nm and Commission Internationale de I'Eclairage coordinates of (0.20, 0.76) for color‐saturated green emission for the electroluminescence peak centered at 534 nm, thus being fully compliant with the latest standard for wide color gamut displays. [ABSTRACT FROM AUTHOR]

This study aims to enhance the optical and thermal properties of cesium-based perovskite nanocrystals (NCs) through surface passivation with organic sulfonate (or sulfonic acid) ligands. Four different phenylated ligands, including sodium β-styrenesulfonate (SbSS), sodium benzenesulfonate (SBS), sodium p-toluenesulfonate (SPTS), and 4-dodecylbenzenesulfonic acid (DBSA), were employed to modify blue-emitting CsPbBr1.5Cl1.5 perovskite NCs, resulting in improved size uniformity and surface functionalization. Transmission electron microscopy and X-ray photoelectron spectroscopy confirmed the successful anchoring of sulfonate or sulfonic acid ligands on the surface of perovskite NCs. Moreover, the photoluminescence quantum yield increased from 32% of the original perovskite NCs to 63% of the SPTS-modified ones due to effective surface passivation. Time-resolved photoluminescence decay measurements revealed extended PL lifetimes for ligand-modified NCs, indicative of reduced nonradiative recombination. Thermal stability studies demonstrated that the SPTS-modified NCs retained nearly 80% of the initial PL intensity when heated at 60 °C for 10 min, surpassing the performance of the original NCs. These findings emphasize the optical and thermal stability enhancement of cesium-based perovskite NCs through surface passivation with suitable sulfonate ligands. [ABSTRACT FROM AUTHOR]

Mn2+ doping has been adopted as an efficient approach to regulating the luminescence properties of halide perovskite nanocrystals (NCs). However, it is still difficult to understand the interplay of Mn2+ luminescence and the matrix self-trapped exciton (STE) emission therein. In this study, Mn2+-doped CsCdCl3 NCs are prepared by hot injection, in which CsCdCl3 is selected because of its unique crystal structure suitable for STE emission. The blue emission at 441 nm of undoped CsCdCl3 NCs originates from the defect states in the NCs. Mn2+ doping promotes lattice distortion of CsCdCl3 and generates bright orange-red light emission at 656 nm. The energy transfer from the STEs of CsCdCl3 to the excited levels of the Mn2+ ion is confirmed to be a significant factor in achieving efficient luminescence in CsCdCl3:Mn2+ NCs. This work highlights the crucial role of energy transfer from STEs to Mn2+ dopants in Mn2+-doped halide NCs and lays the groundwork for modifying the luminescence of other metal halide perovskite NCs. [ABSTRACT FROM AUTHOR]

Abstract Perovskite CsPbBr3 nanocrystals show excellent optical properties. However, the nanocrystals encounter a major challenge of poor stability. In this study, an effective approach is proposed for enhancing the stability of CsPbBr3 nanocrystals via a dual passivation strategy, where the dual passivation layer is composed of alumina (Al2O3) and polymer ethylene‐vinyl acetate (EVA). The Al2O3 coating on the CsPbBr3 surface is realized by in situ oxidation of trimethyl aluminum (TMA), which passivated the surface defects while blocking the intrusion of water and oxygen. The EVA film is formed by a solution method, which can further block the water and oxygen, and form the flexible composite with perovskite CsPbBr3 nanocrystals with enhanced stability toward water and heat. After soaking for 360 h and heating for 5 h, the photoluminescence (PL) intensity is higher than that without passivation. The polymer EVA packaging strategy provided CsPbBr3 with excellent extensibility and flexibility at 100% and 200% tensile rates, the PL intensity remains 91% and 88% of the initial intensity, which returns to the initial value after stretching. The unique dual‐protection structure significantly improves the water and thermal stability of the nanocrystals. The strategy might point out the direction for the future application of perovskites.

Abstract The exceptional optoelectronic properties of lead halide perovskite nanocrystals (PeNCs) in the ultraviolet and visible spectral regions have positioned them as a promising class of semiconductor materials for diverse optoelectronic and photovoltaic applications. However, their limited response to near‐infrared (NIR) light due to the intrinsic bandgap (>1.5 eV) has hindered their applications in many advanced technologies. To circumvent this limitation, it is of fundamental significance to integrate PeNCs with lanthanide‐doped upconversion nanoparticles (UCNPs) that are capable of efficiently converting low‐energy NIR photons into high‐energy ultraviolet and visible photons. By leveraging the energy transfer from UCNPs to PeNCs, this synergistic combination can not only expand the NIR responsivity range of PeNCs but also introduce novel emission profiles to upconversion luminescence with multi‐dimensional tunability (e.g., wavelength, lifetime, and polarization) under low‐to‐medium power NIR irradiation, which breaks through the inherent restrictions of individual PeNCs and UCNPs and thereby opens up new opportunities for materials and device engineering. In this review, we focus on the latest advancements in the development of PeNCs‐UCNPs nanocomposites, with an emphasis on the controlled synthesis and optical properties design for advanced optoelectronic applications such as full‐spectrum solar cells, NIR photodetectors, and multilevel anticounterfeiting. Some future efforts and prospects toward this active research field are also envisioned.

BACKGROUND: The development of new scintillation materials based on fluorescent nanocrystals with a perovskite structure of CsPbBr3 composition and CdSe/ZnS quantum dots is a pressing topic that is being pursued by numerous scientific groups [1–4]. Both of these materials have a high potential for application in this role due to their excellent fluorophore properties, with a quantum yield of luminescence of approximately 100%. Additionally, they possess high values of the effective atomic Zeff number. The photoelectric cross section is dependent on Zeff as (Zeff)5, while the magnitude of X-ray absorption is dependent on Zeff as (Zeff)4/(AE3), where A is the atomic mass of the substance absorbing the γ-quantum and E is the energy of the X-ray photon [5]. AIM: The aim of the study was to develop a technique for fabricating scintillators based on quantum dots and polymer matrices with a high degree of transparency, high temporal stability of luminescence quantum yield, and short luminescence decay times (time of illumination or average lifetime of the substance in the excited state) for gamma-ray registration. MATERIALS AND METHODS: A HAMAMAMATSU R7400U-6 photomultiplier tube was employed to register scintillation signals. A 137Cs source with a γ-quantum energy of 661.7 keV was used as a source of ionizing radiation. RESULTS: At irradiation with γ-quanta of 137Cs isotope samples based on poly(para-methylstyrene) matrix cross-linked with divinylbenzene molecules (10% wt%), activated with naphthalene (10%, primary acceptor), anthracene (1%) and quantum dots/perovskite nanocrystals (0, 1–1.0%, re-emitter), the energy spectrum showed effective Compton scattering of gamma-quanta in matter on atoms included in quantum dots/perovskite nanocrystals. The study revealed that samples devoid of inorganic elements, including quantum dots and perovskite nanocrystals, do not exhibit the Compton effect for gamma-quanta. Furthermore, the paramethylstyrene matrix serves to safeguard perovskite nanocrystals from external influences. The photoluminescence quantum yield of bulk composite materials based on perovskite nanocrystals of the CsPbBr3 composition and poly(paramethylstyrene) remains constant over an extended period, with minimal fluctuations within the margin of error. CONCLUSIONS: Experimental evidence has demonstrated that quantum dots and perovskite nanocrystals encapsulated in various polymer matrices exhibit scintillator properties when subjected to ionizing radiation. The fabricated samples of perovskite nanocrystals/quantum dots and various polymers have been identified as the most promising candidates for use as scintillation material for the registration of X-ray and gamma radiation.

Inkjet printing holds promise for fabricating perovskite nanocrystal (NC) light-emitting diodes (LEDs) by enabling on-demand pattern formation with a colloidal ink. However, this method typically requires high-boiling solvents, necessitating higher annealing temperatures compared to conventional spin-coating processes. In this study, we successfully reduced the annealing temperature of inkjet-printed CsPbBr3 perovskite NC films from 200 to 140 °C by removing the reaction solvent, 1-octadecene (boiling point 315 °C), via a reprecipitation purification process. Annealing the inkjet-printed films at 140 °C under nitrogen conditions in a glovebox suppressed optical quenching by the hole injection layer poly-(3,4-ethylenedioxythiophene):poly-(styrene-sulfonate) (PEDOT:PSS), whereas strong optical quenching occurred during annealing at 140 °C under atmospheric conditions. The inkjet-printed CsPbBr3 NC-LED exhibited a luminance of 944 cd/m2 and an external quantum efficiency of 4.7% following low-temperature annealing of the CsPbBr3 NC film under nitrogen conditions. There findings suggest that low annealing temperatures facilitate the formation of a multilayer structure without optical quenching, thus enhancing LED efficiencies. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Rare earth (RE) ions, with abundant 4f energy level and unique electronic arrangement, are considered as substitutes for Pb2+ in perovskite nanocrystals (PNCs), allowing for partial or complete replacement of lead and minimizing environmental impact. This review provides a comprehensive overview of the characteristics of RE‐doped PNCs, including up‐conversion luminescence, down‐conversion luminescence, and quantum confinement effects, etc. Additionally, RE doping has been found to effectively suppress defect formation, reduce nonradiative recombination, enhance photoluminescence quantum yield (PLQY), and even allow for controlling over the morphology of the nanocrystals. The review also highlights the recent advancements in lead‐free RE‐based perovskites, especially in the case of Eu‐based perovskites (CsEuBr3 and CsEuCl3). Furthermore, it briefly introduces the applications of PNCs in various fields, such as perovskite solar cells (PSCs), luminescent solar concentrators (LSCs), photodetectors (PDs), and light‐emitting diodes (LEDs). A systematic discussion on the luminescence mechanisms of RE‐doped PNCs and lead‐free RE‐based perovskites is provided, along with an outlook on future research directions. The ultimate goal of this review is to provide guidance for the development of RE‐based perovskite optoelectronic devices. Key Scientists: In 2015, Kovalenko et al. pioneered the synthesis of lead‐based perovskite nanocrystals using the thermal injection method. Concurrently, Zhong et al. introduced the ligand‐assisted reprecipitation method. These methods have become the predominant approaches for fabricating lead‐based perovskite nanocrystals. In 2017, Song et al. successfully incorporated various rare earth ions (Ce3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+, and Yb3+) into CsPbCl3 perovskite nanocrystals. They also observed the quantum cutting effect induced by defect states, facilitated by the doping of Yb3+. Gamelin et al. subsequently proposed that CsPbCl3:Yb3+ nanocrystals exhibit quantum cutting effects due to the introduction of charge‐compensating defects (VPb), resulting in the formation of Yb3+‐VPb‐Yb3+ defect complexes with shallow defect levels. In 2020, Zhang et al. successfully doped Nd3+ into CsPbBr3, yielding blue luminescent nanocrystals with a central wavelength of 459 nm and up to 90% photo‐luminescence quantum yield (PLQY). In the same year, Yang et al. achieved the synthesis of pure phase CsEuCl3 perovskite nanocrystals for the first time. In 2022, Paik et al. synthesized Cs3LnCl6 (Ln = Y, Ce, Gd, Er, Tm, Yb, Eu, Tb) nanocrystals using the thermal injection method. In 2023, Zhang et al. successfully introduced Ni2+ doping into CsEuCl3, enhancing the PLQY of CsEuCl3 nanocrystals from 5% to 19.7%. This review focuses on the development history of perovskite nanocrystals, including rare earth‐doped lead‐based perovskite nanocrystals and rare earth‐based lead‐free perovskite nanocrystals, as well as their applications. [ABSTRACT FROM AUTHOR]

The instability and clumping of lead halide perovskite nanocrystals in polar solutions have limited their practical use. In this paper, a convenient and effective surface modification strategy was applied to substitute the typical oleic acid (OA) with 3-bromopropionic acid (BPA) ligand for the one-step synthesis of CsPbBr 3 NCs in the absence of any inert gas atmosphere with water as the non-solvent. Thanks to the synergistic effect of BPA and OAm on the surface of CsPbBr 3 NCs, it has excellent dispersibility while exhibiting excellent stability in water. Even after being fully submerged in water for 168 h, the material can still emit a vibrant green light, and the emission peak position is stable at 520 nm. In contrast, the CsPbBr 3 NCs of the OA ligand were completely burst in water within minutes. This study opens the door for the direct synthesis and preservation of CsPbBr 3 NCs in the aqueous phase, which will be an important step in advancing their large-scale applications in extreme environments. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Rare earth (RE) ions, with abundant 4f energy level and unique electronic arrangement, are considered as substitutes for Pb2+ in perovskite nanocrystals (PNCs), allowing for partial or complete replacement of lead and minimizing environmental impact. This review provides a comprehensive overview of the characteristics of RE‐doped PNCs, including up‐conversion luminescence, down‐conversion luminescence, and quantum confinement effects, etc. Additionally, RE doping has been found to effectively suppress defect formation, reduce nonradiative recombination, enhance photoluminescence quantum yield (PLQY), and even allow for controlling over the morphology of the nanocrystals. The review also highlights the recent advancements in lead‐free RE‐based perovskites, especially in the case of Eu‐based perovskites (CsEuBr3 and CsEuCl3). Furthermore, it briefly introduces the applications of PNCs in various fields, such as perovskite solar cells (PSCs), luminescent solar concentrators (LSCs), photodetectors (PDs), and light‐emitting diodes (LEDs). A systematic discussion on the luminescence mechanisms of RE‐doped PNCs and lead‐free RE‐based perovskites is provided, along with an outlook on future research directions. The ultimate goal of this review is to provide guidance for the development of RE‐based perovskite optoelectronic devices. Key Scientists: In 2015, Kovalenko et al. pioneered the synthesis of lead‐based perovskite nanocrystals using the thermal injection method. Concurrently, Zhong et al. introduced the ligand‐assisted reprecipitation method. These methods have become the predominant approaches for fabricating lead‐based perovskite nanocrystals. In 2017, Song et al. successfully incorporated various rare earth ions (Ce3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+, and Yb3+) into CsPbCl3 perovskite nanocrystals. They also observed the quantum cutting effect induced by defect states, facilitated by the doping of Yb3+. Gamelin et al. subsequently proposed that CsPbCl3:Yb3+ nanocrystals exhibit quantum cutting effects due to the introduction of charge‐compensating defects (VPb), resulting in the formation of Yb3+‐VPb‐Yb3+ defect complexes with shallow defect levels. In 2020, Zhang et al. successfully doped Nd3+ into CsPbBr3, yielding blue luminescent nanocrystals with a central wavelength of 459 nm and up to 90% photo‐luminescence quantum yield (PLQY). In the same year, Yang et al. achieved the synthesis of pure phase CsEuCl3 perovskite nanocrystals for the first time. In 2022, Paik et al. synthesized Cs3LnCl6 (Ln = Y, Ce, Gd, Er, Tm, Yb, Eu, Tb) nanocrystals using the thermal injection method. In 2023, Zhang et al. successfully introduced Ni2+ doping into CsEuCl3, enhancing the PLQY of CsEuCl3 nanocrystals from 5% to 19.7%. This review focuses on the development history of perovskite nanocrystals, including rare earth‐doped lead‐based perovskite nanocrystals and rare earth‐based lead‐free perovskite nanocrystals, as well as their applications. [ABSTRACT FROM AUTHOR]

All inorganic perovskite CsPbX3 (X = Cl, Br, and I) nanocrystals (NCs) have emerged as new semiconductor materials for light-emitting applications due to their high light absorption coefficient, tunable spectrum, and high photoluminescence quantum yields (PLQYs). However, owing to their burst nucleation and growth, the size distribution of CsPbX3 NCs prepared by the conventional homogeneous reaction system is wide, which affects their high color purity. Here, a heterogeneous reaction system was designed to prepare CsPbBr3 NCs with a narrow size distribution by controlling the nucleation and growth kinetics of CsPbBr3 NCs and eliminating the undesired Ostwald ripening effect. The synthesized CsPbBr3 NCs exhibit nearly a unit PLQY and a narrow size distribution. Benefiting from the tight ligands on the surface of NCs that can both stabilize the inorganic nuclei of CsPbBr3 NCs and passivate the Br vacancy defects of the NC surface, the obtained CsPbBr3 NCs have excellent optical stability. In particular, the PLQY of the CsPbBr3 NC colloidal dispersion can be as high as 86% even after 13 cycles of purification with methyl acetate. [ABSTRACT FROM AUTHOR]

Molecular engineering toward the structure of a passivation ligand is essential to improve the photoluminescence (PL) efficiency of perovskite nanocrystals (PNCs). To establish the surface recovery mechanism of red‐emitting CsPb(Br,I)3 NCs with PbI2 additives in the presence of a tightly bound passivation layer, time‐resolved photoluminescence (TRPL) measurements and their chemometric analysis are employed. Two quaternary alkylammonium ligands, didodecyldimethylammonium iodide (DDAI) and tridodecylmethylammonium iodide (TDAI), are used to form a passivation layer, and then their role in the surface defects recovery is investigated by varying the amount of PbI2 additives. It is found that the structural difference between DDAI and TDAI can affect the accessibility of PbI2 additives to surface defects. The TRPL spectra analysis reveals that the ligand passivation with DDAI does not induce discernible lifetime enhancement with using PbI2 additives, but only a non‐radiative pathway is gradually accelerated with increasing the amount of them. The TDAI ligand, however, shows the opposite behavior to give the best PL performance with a distinct molar ratio of TDAI:PbI2, even though the passivation itself gives a lower PL performance. It is argued that the intrinsic structural properties of the TDAI ligand are responsible for the effective surface recovery with the additives. [ABSTRACT FROM AUTHOR]

Although colloidal perovskite nanocrystal (PNC) solution has exhibited near‐unity photoluminescence quantum yield (PLQY), the luminance would be severely quenched when the PNC solution is assembled into thin films due to the agglomeration and fusion of NCs caused by the exfoliation of surface ligands and non‐radiative Förster resonance energy transfer (FRET) from small to large particle sizes, which seriously affected the performances of light‐emitting diodes (LEDs). Here, we used Guanidine thiocyanate (GASCN) and Sodium thiocyanate (NaSCN) to achieve effective CsPbI3 PNC surface reconstruction. Due to the strong coordination ability of these small molecules with the anions and cations on the surface of the PNCs, they can provide strong surface protection against PNC fusion during centrifugal purification process and repair the surface defects of PNCs, so that the original uniform size distribution of PNCs can be maintained and FRET between close‐packed PNC films is effectively suppressed, which allows the emission characteristics of the films to be preserved. As a result, highly oriented, smooth and nearly defect‐free high‐quality PNC thin films are obtained, with PLQY as high as 95.1 %, far exceeding that of the original film, and corresponding LEDs exhibit a maximum external quantum efficiency of 24.5 %. [ABSTRACT FROM AUTHOR]

The optical properties of a photoluminescent material based on CsPbBr3 perovskite nanocrystals were studied in this work. The laser heating of the obtained samples was studied under three different regimes of laser excitation: the photoluminescence band appears in the Stokes region, in the anti-Stokes region, and coincides with the excitation line. It was found that under laser excitation of a certain wavelength, this material is able to demonstrate predominantly anti-Stokes (upconversion) photoluminescence. A method is proposed for estimating the PL quantum yield from data on absorption, photoheating, and the position of the photoluminescence band of a sample at two different wavelengths. The external photoluminescence quantum yield of CsPbBr3 nanocrystals was experimentally determined to be 91 ± 4%. The results of this work can be useful for the development of optical cooling technology and can be used in the development of laser devices based on perovskite materials. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals (NCs), such as MAPbX3 (MA+ = methylammonium; X = Cl, Br, or I), have received attention owing to their excellent optoelectronic properties and ease of integrating with flexible substrates. Lanthanide ion doping is widely used as an effective strategy to enhance the optoelectronic performance of perovskite NCs. However, incorporating the lanthanide dopant and ensuring the emission stability of the perovskite NCs in high‐performance optoelectronic devices remains a major challenge. Herein, the synthesis of Eu2+‐doped MAPbBr3 NCs within the channels of SBA‐15 is presented to improve their stability. The doped MAPbBr3 NC@SBA‐15 composites exhibit significantly improved stability than that of undoped MAPbBr3 NCs. The doped MAPbBr3 NC@SBA‐15 composites exhibit moderate PL quantum yields and excellent stability under ambient conditions and UV irradiation. In addition, the MAEu0.3Pb0.7Br3 NC@SBA‐15 composite applied in white‐light‐emitting diodes (WLEDs) achieves a color rendering index of 73.5. Moreover, MAEu0.3Pb0.7Br3 NC@SBA‐15 can be combined with styrene‐ethylene‐butylene‐styrene to fabricate a flexible direct X‐ray detector, realizing a high sensitivity of 7592.2 µC Gyair−1 cm−2 and a low detection limit of <77 nGyair s−1; this is an outstanding value for a NC‐based flexible direct X‐ray detector. This work serves as a guide for the design of perovskite NCs for both WLEDs and flexible X‐ray detectors. [ABSTRACT FROM AUTHOR]

All‐inorganic lead halide perovskite nanocrystals (NCs) have great optoelectronic properties with promising applications in light‐emitting diodes (LEDs), lasers, photodetectors, solar cells, and photocatalysis. However, the intrinsic toxicity of Pb and instability of the NCs impede their broad applications. Shell‐coating is an effective method for enhanced environmental stability while reducing toxicity by choosing non‐toxic shell materials such as metal oxides, polymers, silica, etc. However, multiple perovskite NCs can be encapsulated within the shell material and a uniform epitaxial‐type shell growth of well‐isolated NCs is still challenging. In this work, lead‐free vacancy‐ordered double perovskite Cs2SnX6 (X = Cl, Br, and I) shells are epitaxially grown on the surface of CsPbX3 NCs by a hot‐injection method. The effectiveness of the non‐toxic double perovskite shell protection is demonstrated by the enhanced environmental and phase stability against UV illumination and water. In addition, the photoluminescence quantum yields (PL QYs) increase for the CsPbCl3 and CsPbBr3 NCs after shelling because of the type I band alignment of the core/shell materials, while enhanced charge transport properties obtained from CsPbI3/Cs2SnI6 core/shell NCs are due to the efficient charge separation in the type II core/shell band alignment. [ABSTRACT FROM AUTHOR]

Highly fluorescent cesium lead‐based (CsPbX3, X═Br, Cl, I) inorganic metal halide perovskites semiconductors have gained immense popularity in the last decade due to the economic and straightforward fabrication techniques involved in these materials along with their excellent electrical and optoelectronic properties. Cesium lead halide nanocrystals are well known for their fluorescence in the visible region with extremely high internal quantum efficiencies; thus making them highly suitable for the fabrication of efficient light‐emitting diodes, transistors and photodetectors. Although perovskite nanocrystals (NCs) are more fluorescent compared to their bulk counterpart, there have been very few reports on the synthesis and characterization of CsPbX3 perovskite NCs. In this work, we have synthesized and investigated the CsPbBr3 and CsPbBr2I NCs to understand the fundamental optoelectronic properties and structural integrity in mixed halide perovskite NCs. We have estimated ~10 nm average particle size of CsPbBr3 nanocrystals from the high‐resolution transmission electron microscopy (HRTEM) while CsPbBr2I has ~16 nm average particle size with slightly higher polydispersity. Most interestingly, we do not observe any phase segregation of bromide and iodide ions in mixed halide perovskite quantum dots due to finite size effect. This is also confirmed by the energy dispersive X‐ray spectroscopy (EDS) mapping data. However, CsPbBr3 nanocrystals are relatively more stable than the mixed halide perovskite nanocrystals due to fewer defects. Anomalous behavior is observed in the photoluminescence intensity with the variation of precursor concentration indicating a complex nature nanoparticle synthesis. [ABSTRACT FROM AUTHOR]

Surface defects of metal halide perovskite nanocrystals (PNCs) substantially compromise the optoelectronic performances of the materials and devices via undesired charge recombination. However, those defects, mainly the vacancies, are structurally entangled with each other in the PNC lattice, necessitating a delicately designed strategy for effective passivation. Here, a synergistic metal ion doping and surface ligand exchange strategy is proposed to passivate the surface defects of CsPbBr3 PNCs with various divalent metal (e.g., Cd2+, Zn2+, and Hg2+) acetate salts and didodecyldimethylammonium (DDA+) via one‐step post‐treatment. The addition of metal acetate salts to PNCs is demonstrated to suppress the defect formation energy effectively via the ab initio calculations. The developed PNCs not only have near‐unity photoluminescence quantum yield and excellent stability but also show luminance of 1175 cd m−2, current efficiency of 65.48 cd A−1, external quantum efficiency of 20.79%, wavelength of 514 nm in optimized PNC light‐emitting diodes with Cd2+ passivator and DDA ligand. The "organic–inorganic" hybrid engineering approach is completely general and can be straightforwardly applied to any combination of quaternary ammonium ligands and source of metal, which will be useful in PNC‐based optoelectronic devices such as solar cells, photodetectors, and transistors. [ABSTRACT FROM AUTHOR]

CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals (PNCs) have been recognized as potential optoelectronic materials due to their excellent optical characteristics. However, their poor stability limits their further practical application, and research on their stability improvement mainly concentrated on green-emitted CsPbBr3 PNCs. Herein, high-stable red, green, and blue three-primary color CsPbX3-nanocrystal/SiO2 (PNC/SiO2) luminescent composites have been synthesized by a simple high-temperature melt-crystallization method, which did not use any solvent or ligand. The sintering conditions for PNC/SiO2 composites were optimized according to the X-ray diffraction and photoluminescence (PL) spectra, which ensured the composite structures and achieved higher PL quantum yield. The optimized red, green, and blue composites can remain at 99%, 90%, and 82% PL intensity after 15 heating loops, performing good thermal stability. To check the application potential, the optimized composites were fabricated as red, green, and blue light-emitting diodes (LEDs), showing high color purity to consist of a wide color gamut. The red, green, and blue LEDs remained at 83%, 82%, and 96% emission intensity and kept their color coordinates after a long working duration, showing excellent stability. The excellent stability and relatively higher color purity of the PNC/SiO2 composites indicate their great potential for commercial background display applications. [ABSTRACT FROM AUTHOR]

Recently, there has been growing interest among researchers in developing efficient photorecording devices using perovskite (PVSK) materials as floating gate layers due to their simplified structure and noncontact, light-responsive characteristics. Since a PVSK-based memory layer can reduce the operating voltage of the device, it can be used for nonvolatile memory applications. Herein, the p-type material pentacene was utilized as the charge transport layer, while methylammonium lead bromide PVSK nanocrystals (NCs) were employed as the floating gate memory layer. Four types of poly-(amic acid) (PAA) polymers were synthesized in combination with PVSK for the memory layer. Compared to conventional polymers, PAA can further fine-tune the influence of energy-level alignment and the crystalline structure of PVSK NCs. The PAA structure consists of carboxylic acid and amide groups that can form Lewis acid–base interactions with PVSK NCs, while these hydrogen-bonding groups can interact with methylammonium to confine crystallite size, thereby passivating defects in PVSK NC films, providing structural stability and effectively optimizing device performance. Among the four synthesized PAA structures, sulfonyldianiline-cyclobutanetetracarboxylic dianhydride (SODA-CBDA) had a sulfone group and cyclobutane ring, possessing electron-withdrawing abilities that lowered the highest occupied molecular orbital level and a conjugation breaker that raised the lowest unoccupied molecular orbital level, resulting in a wider bandgap and stabilized electrons and holes compared to the other PAA structures. The fabricated device required only 1 s to complete electrical erasing and exhibited a stable and high ON/OFF current ratio (∼104) and long-term stability (>104 s) over consecutive device operations. [ABSTRACT FROM AUTHOR]