Luminescent CsPbBr3 Research Articles

Highly luminescent CsPbBr3 perovskite nanocrystal films via the ligand-assisted reaction

Via the ligand-assisted reaction, highly luminescent CsPbBr3 perovskite nanocrystal (PNC) films were synthesized by a simple centrifugal casting process based on the supersaturated recrystallization method. The structure, the optical properties, the morphology, the stability and the potential application of the PNC films were investigated in detail. The results show that under the joint use of OA, DDAB and APTES, the obtained PNC films with 1.5 M DDAB show the strong PL emission with highest quantum yield of 77.5 %, the pure CsPbBr3 structure, the smooth surface and the enhanced stability under UV irradiation. Additionally, the white LED device based on the PNC films obtained here and a commercial red phosphor layer shows excellent optical and color properties and working stability, demonstrating the potential of the PNC films in this study in the field of light-emitting and display.

Highly luminescent and stable CsPbBr3 perovskite nanocrystals coated with polyethersulfone for white light-emitting diode applications.

Simultaneously improving the stability and photoluminescence quantum yield (PLQY) of all inorganic perovskite nanocrystals (NCs) is crucial for their practical utilization in various optoelectronic devices. Here, CsPbBr3 NCs coated with polyethersulfone (PES) were prepared via an in-situ co-precipitation method. The sulfone groups in PES bind to undercoordinated lead ion (Pb2+) on the CsPbBr3 NCs, resulting in significant reduction of surface defects, thus enhancing the PLQY from 74.2% to 88.3%. Meanwhile, the PES-coated NCs exhibit high water resistance and excellent heat and light stability, maintaining over 85% of the initial PL intensity under thermal aging (70°C, 4h) and continuous 365 nm ultraviolet (UV) light irradiation (24 W, 8h) conditions. By contrast, the PL intensity of the control NCs dramatically dropped to less than 40%. Finally, a diode emitting bright white light was fabricated utilizing the PES-coated CsPbBr3 NCs, which exhibits a color gamut of ~110% NTSC standard.

Insight into the Interaction between Perovskite and Water via In Situ PL Measurement

Contrary to widely held view that water induces negative effect on lead halide perovskites, publications on active role of water in photoluminescence (PL) and stability of perovskites have been emerged recently. Until now, comprehensively understanding the interaction between perovskite and water is absolutely necessary for its highly correlation with the practical application and remains a significant challenge. In this study, we utilize in situ PL measurement, ex situ transmission electron microscopy, UV–vis spectroscopy and X-ray photoelectron spectroscopy to track and reveal the interaction of perovskite with water. For the organic-inorganic lead bromide perovskite, water induces amorphization, degradation of MAPbBr3, as well as formation of PbBrOH. As-obtained MAPbBr3@PbBrOH composites exhibit high PL quantum yield (QY) of 41.8–57.0% and robust water stability for the protection from PbBrOH. For cesium lead bromide perovskite, water facilitates the phase transition from non-luminescent Cs4PbBr6 to luminescent CsPbBr3, and could also instigate the formation of PbBrOH. However, the water-induced Ostwald maturation of CsPbBr3 and structure defects brought by the phase transition ultimately lead to the production of large CsPbBr3 crystals or CsPbBr3@PbBrOH composites with ultralow PLQY. This work provides valuable insights into the interaction between perovskite and water, and holds important implications for comprehending the instability of lead halide perovskites.

Solvent-free blending of CsPbBr3 and commercial polymer: Interface-visualization, bandgap engineering and improved stability in 3D printing

Metal halide perovskites (MHPs) encapsulated in polymer have enhanced stability and processability. Most of the MHPs/polymer composites are fabricated in organic solvents and the interaction between MHPs and polymer matrix is rarely reported. In this work, solvent-free twin-screw blending is adopted for CsPbBr3@PolymerA/PolymerB (PolymerA = polypropylene (PP), polyethylene (PE) or poly(butylene-adipate-co-terephthalate) (PBAT), PolymerB = polylactic acid (PLA)) composites preparation. Different factors including compatibilizer addition, polymer composition and CsPbBr3 feeding ratio are used to investigate the interaction between MHPs and polymer matrix. According to the wetting coefficient calculation, transmission electron microscope (TEM) and scanning electron microscope (SEM) results, CsPbBr3 is mostly distributed in the interface of PE/PLA blending. As a result, the luminescent CsPbBr3 can be used for interface marker to study the polymer interface morphology. The interpenetration morphology of polymer interface allows CsPbBr3 to show the most efficient green emission and convenient halogen exchange. Thus, the optical emission and absorption can be tuned from blue to red. PE/PLA blending endows CsPbBr3@PE5/PLA5 with 3D printing ability and improved stability against to the water, UV light and heat.

Chemical transformation mechanism for blue-to-green emitting CsPbBr3 nanocrystals.

Recently, metal-halide perovskites have rapidly emerged as efficient light emitters with near-unity quantum yield and size-dependent optical and electronic properties, which have attracted considerable attention from researchers. However, the ultrafast nucleation rate of ionic perovskite counterparts severely limits the in-depth exploration of the growth mechanism of colloidal nanocrystals (NCs). Herein, we used an inorganic ligand nitrosonium tetrafluoroborate (NOBF4) to trigger a slow post-synthesis transformation process, converting non-luminescent Cs4PbBr6 NCs into bright green luminescent CsPbBr3 NCs to elucidate the concrete transformation mechanism via four stages: (i) the dissociation of pristine NCs, (ii) the formation of Pb-Br intermediates, (iii) low-dimensional nanoplatelets (NPLs) and (iv) cubic CsPbBr3 NCs, corresponding to the blue-to-green emission process. The desorption and reorganization of organic ligands induced by NO+ and the involvement of BF4- in the ligand exchange process played pivotal roles in this dissolution-recrystallization of NCs. Moreover, controlled shape evolution from anisotropic NPLs to NCs was investigated through variations in the amount of NOBF4. This further validates that additives exert a decisive role in the symmetry and growth of nanostructured perovskite crystals during phase transition based on the ligand-exchange mechanism. This finding serves as a source of inspiration for the synthesis of highly luminescent CsPbBr3 NCs, providing valuable insights into the chemical mechanism in post-synthesis transformation.

Classical molecular dynamics simulations of CsPbBr3 perovskite quantum dots embedded sodium borosilicate glasses

We have simulated the configuration of perovskite CsPbBr3 quantum dot (QD), sodium borosilicate (SBS) glass matrix, and the combination of these two, namely CsPbBr3 QDs embedded SBS glass. We delineate a microscope porthole containing ∼100,000 atoms and with a dimension of ∼30 nm × 30 nm × 1 nm, using the classical molecular dynamics (CMD) benefiting from graphics processing unit (GPU) acceleration. We quantify the structural properties of glass matrix and determined the crystallization of QDs, in excellent agreement with experimental observations. Based on analysis the of boron coordination, structural undulation influenced by the K value (KSiO2/B2O3), we demonstrate the significant compositional repulsion in the combination derived from electronegative nonmetal elements, namely oxygen (O) and bromine (Br). As the K value decreases, indicating an increase in the proportion of B2O3 and a decrease in the proportion of SiO2, the [BO3]/[BO4] ratio increases, resulting in a glass matrix with a stronger repulsive 'anionic sea' and a more relaxed encapsulated environment for CsPbBr3 QD. This creates greater repulsion for the allocation of oxide and bromide, and a more suitable space for the crystallization of CsPbBr3 clusters, which in turn regulates the formation of CsPbBr3 QDs. These results constructively extend our understanding of the microstructure of CsPbBr3 QDs embedded SBS glasses, and provide valuable insights for the engineering of CsPbBr3 QDs in SBS glasses on high luminescent CsPbBr3 QDs embedded glasses.

Enhanced luminescence and high stability in Gd3+-doped CsPbBr3 perovskite quantum dots glasses for X-ray detection

The highly luminescent CsPbBr3 perovskite quantum dots (PQDs) glass has shown great potential for applications in X-ray radiation. In this study, the synthesis, crystallization behavior, structural photoluminescence (PL), and X-ray excited luminescence (XEL) of new scintillation luminescent ion Gd3+-service behavior studies were conducted to evaluate the effectiveness of the Gd3+-doped PQDs glasses as X-ray scintillators. The direct band gap semiconductor property makes it suitable for successful detection of X-ray radiation and allows for efficient absorption and emission of X-ray photons, leading to enhanced scintillation performance. These findings highlight the potential of Gd3+-doped CsPbBr3 PQDs glasses as promising materials for X-ray scintillation applications.

Green synthesis of highly luminescent CsPbBr3 quantum dots through silica coating and post-treatment with ligands

All-inorganic perovskite quantum dots (PQDs) have received considerable attentions due to their fascinating optical properties. However, the mainstream preparation methods rely on toxic solvents, raising significant environmental and safety concerns. In this work, ethyl acetate was chosen as the environmentally friendly anti-solvent to prepare silica-coated CsPbBr3 PQDs using a aminoalkoxysilane-assisted reprecipitation–encapsulation method. The as-prepared PQDs exhibited tunable emission wavelength and a medium photoluminescence quantum yield (PLQY) of 60%. Furthermore, CsPbBr3 PQDs were post-treated by different ligands with the aim of passivating surface defects. This strategy successfully mitigated the presence of surface defects and minimized non-radiative recombination losses in PQDs. As a result, the PLQY (achieving up to 73%) and stability of PQDs were substantially enhanced (luminescence stability improved by about 40% under the same test conditions). Our studies offer a novel approach for the environmentally friendly large-scale production of PQDs, opening up new possibilities for their practical applications.

Surfactant-Dependent Bulk Scale Mechanochemical Synthesis of CsPbBr3 Nanocrystals for Plastic Scintillator-Based X-ray Imaging.

We report a facile, solvent-free surfactant-dependent mechanochemical synthesis of highly luminescent CsPbBr3 nanocrystals (NCs) and study their scintillation properties. A small amount of surfactant oleylamine (OAM) plays an important role in the two-step ball milling method to control the size and emission properties of the NCs. The solid-state synthesized perovskite NCs exhibit a high photoluminescence quantum yield (PLQY) of up to 88% with excellent stability. CsPbBr3 NCs capped with different amounts of surfactant were dispersed in toluene and mixed with polymethyl methacrylate (PMMA) polymer and cast into scintillator discs. With increasing concentration of OAM during synthesis, the PL yield of CsPbBr3/PMMA nanocomposite was increased, which is attributed to reduced NC aggregation and PL quenching. We also varied the perovskite loading concentration in the nanocomposite and studied the resulting emission properties. The most intense PL emission was observed from the 2% perovskite-loaded disc, while the 10% loaded disc exhibited the highest radioluminescence (RL) emission from 50 kV X-rays. The strong RL yield may be attributed to the deep penetration of X-rays into the composite, combined with the large interaction cross-section of the X-rays with the high-Z atoms within the NCs. The nanocomposite disc shows an intense RL emission peak centered at 536 nm and a fast RL decay time of 29.4 ns. Further, we have demonstrated the X-ray imaging performance of a 10% CsPbBr3 NC-loaded nanocomposite disc.

Dual-phase CsPbBr3–CsPb2Br5 perovskite scintillator for sensitive X-ray detection and imaging

Cesium lead bromide and its derivatives have recently attracted the scientific community for X-ray detection and imaging due to their effective atomic number, strong scintillating luminescence, fast scintillating decay time, and tunable optical bandgap, despite their poor stability against ultraviolet (UV) illumination, moisture, and thermal degradation. Here, we report the synthesis of a highly luminescent and stable dual-phase CsPbBr3–CsPb2Br5 perovskite nanocrystal (PNCs) system prepared using the hot-injection method for scintillation application. CsPb2Br5 developed on the surface of the CsPbBr3 reduces the surface defect density and greatly enhances the photostability, water resistance, thermal stability, and luminescence properties of the CsPbBr3 nanocrystals. Based on the excellent stability of PNCs in various environments, we mixed the PNCs with polystyrene (PS) and spin-coated the glass plate to evaluate the optical and scintillation properties. The dual-phase CsPbBr3–CsPb2Br5 exhibits a strong green emission at 522 nm with a photoluminescence quantum yield of 65.2% and a fast response time of 2.93 ns under UV excitation. Under X-ray irradiation, CsPbBr3–CsPb2Br5 PNCs exhibited excellent linear response as a function of the dose rate at 50 keV and a low detection limit of 1.130 μGyair s−1, which is less than the typical medical imaging dose (5.5 μGyair s−1) and a light yield of 19,200 photons/MeV. Moreover, the CsPbBr3–CsPb2Br5 scintillating film displays excellent imaging ability with a spatial resolution of up to 8.19 lp/mm at a modulation transfer function (MTF) of 0.2 under an exposure dose of 46.96 μGyair s−1. These findings show that the dual-phase CsPbBr3–CsPb2Br5 structure can be a promising fast scintillating material for X-ray imaging in medical and industrial applications.

A hierarchically porous MOF confined CsPbBr3 quantum dots: Fluorescence switching probe for detecting Cu (II) and melamine in food samples

The hypersensitivity of Perovskite quantum dots (PeQDs) towards external environmental conditions and the water quenching of their fluorescence have limited their practical analytical applications. In this work highly luminescent CsPbBr3 was confined into a hierarchically porous ZIF-8 metal organic framework (HZIF-8) through a simple two step in situ growth method. XRD, FTIR, SEM, TEM, and XPS investigations confirmed the successful synthesis of the CsPbBr3/HZIF-8 nanocomposite. CsPbBr3 PeQDs are uniformly distributed within the HZIF-8 MOF matrix and exhibited intense green emission at 510 nm with a FWHM value of 25 nm in ambient conditions. The nanocomposite showed enhanced stability against moisture and UV light. The intense PL emission of the nanocomposite was well maintained in an aqueous solution also, with no noticeable change in fluorescence characteristics for 15 days of storage in aqueous solution. The CsPbBr3/HZIF-8 composite was then utilized as an on–off-on luminescent probe for the detection of Cu2+ metal ions and melamine in real samples. Because of the porous nature of the MOF, the target analytes can be quickly located and this nanosensor is found to be very sensitive toward Cu2+ and melamine detection. A linear relationship from 3 to 500 nM and 30–1500 nM was found for melamine and Cu2+ under an optimal experimental condition, with a limit of detection value of around 4.66 nM and 2.64 nM for Cu2+ and melamine respectively.

Vacuum-deposited perovskite CsPbBr3 thin-films for temperature-stable Si based pure-green all-inorganic light-emitting diodes

Metal halide perovskite light-emitting diodes (PeLEDs) are excellent candidates in the field of lighting and display due to their outstanding optical-electrical properties. However, the solution-processed technology of perovskite films and the organic electron/hole transport layers of PeLEDs make it still challenging to improve the operational stability of devices. Herein, we successfully prepared highly luminescent CsPbBr3 perovskite films via vacuum-deposited method and then fabricated all-inorganic PeLEDs with the heterostructure of p-NiO/CsPbBr3/n-Si. Our device exhibits pure-green emission with a wavelength of 527 nm, a narrow full width at half-maximum of 18 nm, and a maximum luminance of 51933 cd/m2, representing one of the best brightness pure-green PeLEDs. Most importantly, the PeLEDs exhibited great thermal stability with a heat resistance up to 80 °C. The electroluminescence peak position of the PeLEDs remains consistent when the ambient temperature increases from 40 °C to 110 °C. Moreover, the all-inorganic PeLEDs can maintain their good luminescence performance after seven thermal cycling tests (30 °C–100 °C). This work not only demonstrated a facile strategy to prepare high-quality pure-green CsPbBr3 perovskite films, but also provided an important all-inorganic device structure for high thermal stability of PeLED.

Decyl disulfide surface treatment improved photoluminescence quantum yield and stability of blue-emitting CsPbBr3 nanoplatelets

Improving the photoluminescence quantum yields (PL QYs) and stability of blue-emitting CsPbBr3 nanoplatelets (NPLs) is essential for the application in high-quality displays. Herein, highly luminescent CsPbBr3 NPLs with PL peak at 462 nm were prepared by a modified supersaturated recrystallization synthesis strategy at room temperature. The resulting blue CsPbBr3 NPLs show high PL QY of 98% and a full width at half maximum of 13 nm, benefiting from the decyl disulfide (DF) surface treatment. Besides, the DF-treated CsPbBr3 NPLs show lower Urbach energy (15 meV) and more outstanding water, acetone, and UV-light resistance stabilities than the pristine ones, suggesting that the surface ligand treatment can reduce Br− vacancy defects and inhibit the non-radiative recombination process. Based on the temperature-dependent PL, the exciton binding energy of CsPbBr3 NPLs is found to increase from 109 to 201 meV after DF treatment. Finally, light-emitting diodes based on the treated CsPbBr3 NPLs were fabricated.

Efficient Ligand Passivation Enables Ultrastable CsPbX3 Perovskite Nanocrystals in Fully Alcohol Environments

AbstractHalide perovskite nanocrystals (PNCs) have demonstrated their wide potential to fabricate efficient optoelectronic devices and to prepare promising photocatalysts for solar‐driven photo(electro)chemical reactions. However, their use in most of the practical applications is limited due to the instability of PNCs in polar environments. Here, the preparation of non‐encapsulated CsPbX3 nanocrystals dispersed in fully alcohol environments, with outstanding stability through surface defect passivation strategy is reported. By using didodecyldimethylammonium bromide (DDAB) during material post‐treatment, highly luminescent CsPbBr3 PNCs with remarkable stability in methanol/butanol medium up to 7 months with near‐unity photoluminescence quantum yield are achieved. This approach is extrapolated to stabilize iodine‐based CsPbBr3‐xIx and CsPbI3 PNCs, showing an improvement of their photoluminescence features and stability in these high polar alcohols up to 6 h. DDAB mediates the defect suppression through ligand exchange and avoids the full permeation of alcohol to be in contact with the PNCs. In this context, DDAB induces ionization of alcohol molecules to strengthen the surface passivation. The findings open the door to the development of long‐term stable CsPbX3 PNCs with high optical performance to be used in polar environments.

Interfacial modification for the fabrication of Silicon-based green perovskite Light-Emitting diodes

Perovskite light-emitting diodes (PeLEDs) are promising candidates for display and solid-state lighting. Different from ITO-based devices, the Si-based PeLEDs are of significant application potential in integrated optoelectronics. Here we demonstrate the fabrication of CsPbBr3 PeLEDs on n-Si by tailoring the interfaces of perovskite layers. Green electroluminescence is achieved by spin-coating of CsPbBr3 nanofilms sandwiched within the ethoxylated polyethyleneimine (PEIE) modified ZnO nanofilms as the electron transport layers on Si, and the surficial residual Poly(9-vinylcarbazole) (PVK) layers formed by simple addition in the anti-solvent without additional process. The removal of surficial ligands and the crystallization of atomic layer deposited ZnO nanofilms by annealing are critical for the subsequent deposition of luminescent CsPbBr3 layers, and the PVK layers acting as the hole transport layer enhance the resistance to ambient environment. The thickness control of the PEIE-modified ZnO and residual PVK layers results in intense luminance with good stability, the emission peaking at 500 nm exhibits the external quantum efficiency of 5.1 % and the maximum luminance of 7280 cd/m2. This approach on Si-based PeLEDs would be of application potential in the photonics compatible with micro-electronics, and paves the way for the commercialization of low-cost perovskites and printed electronic devices.

CsPbBr3@PbBrOH 3D/1D molecular matrix for a high-performance scintillator

All-inorganic cesium lead halide perovskite nanocrystals (NCs) have become highly sought-after materials for X-ray detection and imaging because of their outstanding intrinsic electronic and optical properties. However, because of their highly ionic crystal structure, perovskite materials suffer severe moisture, thermal, and photo instability problems, which hinder their commercialization. To resolve this annoying problem, three-dimensional (3D)/1D CsPbBr3@PbBrOH composite structures in terms of molecular structure are designed by incorporating highly luminescent 3D CsPbBr3 NCs into a 1D PbBrOH matrix to form an “emitter-in-matrix”. The prepared CsPbBr3@PbBrOH exhibits excellent stability without sacrificing photoluminescence quantum yield. Meanwhile, 1D PbBrOH can be considered a perfect host, and the presence of heavy atom Pb in its matrix enhances X-ray absorption. The luminescent CsPbBr3 NCs embedded in an inert PbBrOH host are subjected to X-ray detection and imaging. The CsPbBr3@PbBrOH scintillator shows bright radiation luminescence and sensitive response to X-ray signals. In addition, the scintillator is made into a thin film screen for imaging, obtaining a clear image of the transmission electron microscopy grid hidden inside the capsule, and the resolution of CsPbBr3@PbBrOH film is calculated to be as high as 50 lp mm−1. This property of CsPbBr3@PbBrOH scintillators demonstrates their promising application prospects for ionizing radiation detection, particularly for X-ray imaging.

Morphology dependent light-induced photoluminescence enhancement of CsPbBr3 microcrystals.

Herein, we report a facile method for growing CsPbBr3 cube and prism microcrystals by microspacing in-air sublimation. Morphology-dependent photoluminescence behavior investigation reveals that the CsPbBr3 cubes show higher photoluminescence quantum yield and longer PL lifetime than the prisms. In contrast, CsPbBr3 prisms exhibit more considerable light-induced photoluminescence enhancement.

High-quality luminescent CsPbBr3 perovskite nanocrystals prepared by a facile two-phase method

Cesium lead halide perovskite nanocrystals (PNCs) have great potential in the field of lighting and display due to their excellent optical properties. The preparation of high-quality PNCs has always been the focus of scientific research. Herein, we present a facile two-phase method to synthesize high-quality CsPbBr3 nanoparticles. Both toluene and water served as reaction media and oleic acid as a strong bonding ligand was employed to synthesize the CsPbBr3 PNCs. High-quality CsPbBr3 PNCs with good crystallinity, narrow size distributions, and well surface passivation have been synthesized successfully. This study offers an alternative strategy for the preparation of high-quality perovskite materials.

Fabrication of Intrinsic, Elastic, Self-healing, and Luminescent CsPbBr3 Quantum Dot-Polymer Composites via Thiol–Ene Cross-Linking

Here, we offer a straightforward approach for making elastic, self-healing, and light-conversion material, in which CsPbBr3 quantum dots (QDs) form a strong bond with a designed copolymer including elastic behavior based on the mechanical characteristics of polyisoprene and reversible bonding moieties for self-healing function. This designed composite film has highly luminescent and typically elastic properties, including good ultimate strength (∼0.14 N/mm2) and high stretchability (∼486%). The copolymer matrix exhibited excellent compatibility with CsPbBr3 QDs, in which they maintained their uniform distribution within the network after a serial stretching process due to the strong bond between copolymers and CsPbBr3 QDs. Furthermore, the composite film dynamic network is capable of 90% self-healing efficiency at room temperature without the need of any healing stimulus, heat, plasticizer, or solvent. This simple method suggested a relatively easy approach to a stable, elastic, and luminescent CsPbBr3 QD-based composite film that opens up the potential of fully stretchable light conversion material for light-emitting diodes.

Hydrochromic CsPbBr3-KBr Microcrystals for Flexible Anti-Counterfeiting and Wearable Self-Powered Biomechanical Monitoring

Metal-halide perovskites (MHPs) featured with excellent photoelectronic properties and low-temperature solution processability are emerging as desired candidates for next-generation wearable and portable electronics. However, irreversible emission properties quenching of MHPs in the presence of water has severely impeded their versatile applications. Here, we present a facile water–ethanol assisted co-precipitation strategy for cost-effective and eco-friendly fabrication of hydrochromic smart luminescent CsPbBr3-KBr microcrystals (CPB-K). Interestingly, the as-prepared CPB-K can achieve reversible transition between luminescent and non-luminescent state upon the water removal/exposure owing to the dissolution/recrystallization of luminescent CsPbBr3 nanocrystals with the help of KBr salts. The coating of polydimethylsiloxane (PDMS) effectively prevents the destruction of CPB-K and maintains its green emission upon moisture. Further, by leveraging the hydrochromic CPB-K and water-resistant CPB-K/PDMS characteristic synergistically realize multiple encryption effects of information, and the hidden information can be clearly identified upon moisture decryption. Because of electrical and dielectric properties of MHPs, a flexible triboelectric nanogenerator (TENG) made from CPB-K/PDMS film as friction layer has been constructed with maximum open-circuit voltage of 43.4 V (loading CPB-K of 20 wt%), about 1.8 times that of the pristine PDMS-based TENG. Additionally, we demonstrate a self-powered wearable sensor based on CPB-K/PDMS TENG for real-time biomechanical monitoring with electrical signals. This work provides an eco-friendly fabrication approach for perovskite-based smart luminescent materials, which further opens up the possibility to expand their diverse applications in wearable electronics.