Lead Bromide Perovskite Nanocrystals Research Articles

Direct Observation of Size-Dependent Phase Transition in Methylammonium Lead Bromide Perovskite Microcrystals and Nanocrystals.

Methylammonium (MA) lead halide perovskites have been widely studied as active materials for advanced optoelectronics. As crystalline semiconductor materials, their properties are strongly affected by their crystal structure. Depending on their applications, the size of MA lead halide perovskite crystals varies by several orders of magnitude. The particle size can lead to different structural phase transitions and optoelectronic properties. Herein, we investigate the size effect for phase transition of MA lead bromide (MAPbBr3) by comparing the temperature-dependent neutron powder diffraction patterns of microcrystals and nanocrystals. The orthorhombic-to-tetragonal phase transition occurs in MAPbBr3 microcrystals within the temperature range from 100 to 310 K. However, the phase transition is absent in nanocrystals in this temperature range. In this work, we offer a persuasive and direct evidence of the relationship between the particle size and the phase transition in perovskite crystals.

Size-Dependent Phonon-Assisted Anti-Stokes Photoluminescence in Nanocrystals of Organometal Perovskites.

Anti-Stokes photoluminescence (ASPL), which is an up-conversion phonon-assisted process of the radiative recombination of photoexcited charge carriers, was investigated in methylammonium lead bromide (MALB) perovskite nanocrystals (NCs) with mean sizes that varied from about 6 to 120 nm. The structure properties of the MALB NCs were investigated by means of the scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. ASPL spectra of MALB NCs were measured under near-resonant laser excitation with a photon energy of 2.33 eV and they were compared with the results of the photoluminescence (PL) measurements under non-resonant excitation at 3.06 eV to reveal a contribution of phonon-assisted processes in ASPL. MALB NCs with a mean size of about 6 nm were found to demonstrate the most efficient ASPL, which is explained by an enhanced contribution of the phonon absorption process during the photoexcitation of small NCs. The obtained results can be useful for the application of nanocrystalline organometal perovskites in optoelectronic and all-optical solid-state cooling devices.

Protein-Mediated Aqueous Synthesis of Stable Methylammonium Lead Bromide Perovskite Nanocrystals: Implications for Biological and Environmental Applications

Protein-Mediated Aqueous Synthesis of Stable Methylammonium Lead Bromide Perovskite Nanocrystals: Implications for Biological and Environmental Applications

Experimental demonstration of weak chirality enhancement by hybrid perovskite nanocrystals using photonic spin Hall effect

Abstract Chiral perovskites have attracted considerable attention as excellent spin-emitting materials for applications in spintronics, quantum optics, and biological. Especially in drug development of biological, weak chirality molecules are frequently selected to reduce the side effects of toxics, and there is a common defect for accurately detecting the weak chirality with common methods at room temperature. In this study, formamidine lead bromide perovskite nanocrystals (FAPbBr3 NCs) were coated with chiral ligands, whose chirality was too weak to be observed in the visible region at room temperature. Thus, by characterizing the transverse shift of photonic spin Hall effect (SHE), the accurate discrimination of weak chirality in the visible region was achieved successfully. By measuring the shift value and light spot splitting of photonic SHE at the same concentration, NEA-coated FAPbBr3 NCs can effectively enhance the chirality of naphthalene ethylamine (NEA) ligands when under the mutually reinforcement of chiral molecular and inorganic parts. In addition, we furtherly clearly distinguished the tiny chiral distinction of NEA-coated FAPbBr3 NCs with different particle sizes, which revealed that the chirality decreases with the increase of particle size. These findings could provide effective solutions for the detection and application of weak chirality in hybrid perovskite nanocrystals in universal environment.

Novel Composite of Nickel Thiocyanate‐Based All‐Inorganic Lead Bromide Perovskite Nanocrystals with Enhanced Luminescent and Stability for White Light‐Emitting Diodes (Adv. Mater. Interfaces 24/2022)

Novel Composite of Nickel Thiocyanate‐Based All‐Inorganic Lead Bromide Perovskite Nanocrystals with Enhanced Luminescent and Stability for White Light‐Emitting Diodes (Adv. Mater. Interfaces 24/2022)

Stabilizing and accessing across ternary phase cesium lead bromide perovskite nanocrystals: thermodynamic and kinetic controls

Lead halide perovskites with fascinating optoelectronic properties have enabled rapid advancement and development in photovoltaics and light-emitting diodes. However, accessing and stabilizing the complex ternary phase space diagram (Cs-Pb-Br) of perovskites including 3 D nanocrystals, 2 D nanoplatelets, and 0 D hexagonal platelets with desirable optoelectronic properties further requires a deeper understanding of the thermodynamic and kinetic aspects regarding the growth of lead halide perovskite nanocrystals. In this work, we have mapped out the multivariant synthetic design spaces observed in the ternary phase diagram of Cs-Pb-Br to evaluate the effect of controlling thermodynamic equilibrium state (e.g. chemical potentials of the Cs:Pb ratio) and growth kinetics with ligand concentration (oleylamine). Further in-situ tracking of reversible phase transformation with the addition of oleylamine (forward) and PbBr2 (reverse) exhibiting distinctive spectroscopic signatures between 3 D and 0 D phases (vice versa) can provide insight into the reversible phase transformation mechanism and important role of PbBr2 species that can modify the bonding motif and connectivity of [PbBr6]4- octahedral frameworks.

Unraveling the role of hydrogen bromide in the growth of cesium lead bromide perovskite nanocrystals

Hydrogen bromide (HBr) could substantially improve the quality of cesium lead bromide perovskite (CsPbBr3) nanocrystals (NCs) and greatly enhance their optoelectronic performance. However, clarifying the role of HBr in the growth of CsPbBr3 NCs has been a substantial challenge thus far. Herein, we design an in situ cryogenic photoluminescence system using liquid nitrogen to unravel the role played by HBr in the growth of CsPbBr3 NCs. Compared with no HBr (∼40 s), HBr improves the nucleation rate of CsPbBr3 NCs about two times (∼20 s), and its emission peak also exhibits a redshift of ∼30 nm. Thus, we conclude that HBr accelerates the nucleation rate of CsPbBr3 NCs and extends their growth stage, affording the generation of large grains. Perovskite light-emitting diodes based on CsPbBr3 NCs with added HBr also exhibit an outstanding performance. These outcomes provide new insights into the role of HBr in CsPbBr3 NCs and help prepare high-quality CsPbBr3 NCs for use in the fabrication of efficient CsPbBr3 NC-based optoelectronic devices.

Novel Composite of Nickel Thiocyanate‐Based All‐Inorganic Lead Bromide Perovskite Nanocrystals with Enhanced Luminescent and Stability for White Light‐Emitting Diodes

AbstractDoping of CsPbBr3 perovskite nanocrystals (PNCs) to achieve excellent material properties is accelerating due to their increasing use in optoelectronic devices. Herein, a novel composite of CsPbBr3 PNCs with nickel thiocyanate Ni(SCN)2 is reported, exhibiting stronger photoluminescence (PL) and more extended stability. The addition of Ni(SCN)2 at different molar concentrations reduces the surface trap states of the host PNCs. Therefore, the microstrain, dislocation density, PL emission linewidth, and Urbach energy decrease, resulting in an increased photoluminescence quantum yield (PLQY) from 72% to high above 90%. When stored in the ambient atmosphere for 120 days, the PLQY of doped PNCs is maintained by more than four times compared to host PNCs. A combination of 3D‐printed conversion layers containing green‐, yellow‐, and red‐emitting doped PNCs with blue light‐emitting diodes results in stable white light with superior color qualities. Hence, new composites with desired properties are developed as an alternative to conventional color phosphors.

Colorimetric paper test strips based on cesium lead bromide perovskite nanocrystals for rapid detection of ciprofloxacin hydrochloride

The detection of drugs containing hydrochloric salt with conventional methods is time consuming and expensive. In this work, upon exposure to ciprofloxacin hydrochloride at different concentrations, the emission from CsPbBr3 NCs shifts to the blue from 513 nm to 442 nm. CsPbBr(3−x)Cl x NCs are formed by the ion exchange and substitution of Br− and Cl− ions from surface to core of NCs. The first-principles calculations suggest that the substitution of Br− by Cl− ions plays a critical role in the tuning of the energy bandgap. The color of paper test strips changes immediately after exposure to different Ciproxan solutions. We propose that this rapid and portable method has a high potential application in other chloride salts for food safety.

Methylammonium Lead Bromide Perovskite Nano-Crystals Grown in a Poly[styrene-co-(2-(dimethylamino)ethyl Methacrylate)] Matrix Immobilized on Exfoliated Graphene Nano-Sheets.

Development of graphene/perovskite heterostructures mediated by polymeric materials may constitute a robust strategy to resolve the environmental instability of metal halide perovskites and provide barrierless charge transport. Herein, a straightforward approach for the growth of perovskite nano-crystals and their electronic communication with graphene is presented. Methylammonium lead bromide (CH3NH3PbBr3) nano-crystals were grown in a poly[styrene-co-(2-(dimethylamino)ethyl methacrylate)], P[St-co-DMAEMA], bi-functional random co-polymer matrix and non-covalently immobilized on graphene. P[St-co-DMAEMA] was selected as a bi-modal polymer capable to stabilize the perovskite nano-crystals via electrostatic interactions between the tri-alkylamine amine sites of the co-polymer and the A-site vacancies of the perovskite and simultaneously enable Van der Waals attractive interactions between the aromatic arene sites of the co-polymer and the surface of graphene. The newly synthesized CH3NH3PbBr3/co-polymer and graphene/CH3NH3PbBr3/co-polymer ensembles were formed by physical mixing of the components in organic media at room temperature. Complementary characterization by dynamic light scattering, microscopy, and energy-dispersive X-ray spectroscopy revealed the formation of uniform spherical perovskite nano-crystals immobilized on the graphene nano-sheets. Complementary photophysical characterization by UV-Vis absorption, steady-state, and time-resolved fluorescence spectroscopy unveiled the photophysical properties of the CH3NH3PbBr3/co-polymer colloid perovskite solution and verified the electronic communication within the graphene/CH3NH3PbBr3/co-polymer ensembles at the ground and excited states.

Wavelength Tunable Aqueous CsPbBr3-Based Nanoprobes with Ultrahigh Photostability for Targeted Super-Resolution Bioimaging.

Single molecule localization microscopy (SMLM) is indispensable in the visualization of cellular microstructures. However, current SMLM imaging materials, from organic fluorophores to quantum dots, still lack the requirement of increasing need for multiple targets of interest due to their broad emission. Here, by one-step encapsulating hydrophilic cesium lead bromide perovskite nanocrystals (CsPbBr3 NCs) into functionalized polyethylene glycol (PEG), a core-shell nanocomposite of CsPb(Cl(1-x)/Brx)3@PEG (0 < x < 1) was presented as a wavelength-tunable fluorescent probe with the narrow full width at half-maximum (fwhm) as 11 nm. The layer of functionalized PEG endows CsPbBr3 NCs with a broad spectral tunability from 521 to 431 nm, superior photostability for several years, and the ability to be further surface functionalized. The CsPb(Cl(1-x)/Brx)3@PEG exhibits a sub-10 nm localization precision and 10-fold enhanced spatial resolution. Using exosomes with small sizes less than 150 nm as the imaging target, CsPb(Cl(1-x)/Brx)3@PEG realized the distinction of two adjacent exosomes by SMLM. Moreover, after being modified with biotin, CsPb(Cl(1-x)/Brx)3@PEG was universally used for SMLM imaging of cellular microstructures. The excellent photostability and narrow fwhm indicated that such a CsPbBr3-based nanoprobe has great potential as a commercial dye for multitarget super-resolution bioimaging applications.

Probing the effect of a glass network on the synthesis and luminescence properties of composite perovskite glasses [Invited

All-inorganic cesium lead bromide perovskite nanocrystals (PNCs) are highly promising candidates for various optoelectronic and photonic devices. However, poor stability upon exposure to moisture and lead toxicity issues significantly limit their applications. A modern and promising strategy on resolving these issues is the encapsulation of highly luminescent (PNCs) within transparent inorganic oxide glasses. While the encapsulation procedure effect on the development and properties of the so-formed PV-Glasses has been explored in detail, there is lack of understanding the influence of the selected glass composition and network type on the outcome of the synthesis. Herein we report on the synthesis and photoluminescence properties of composite perovskite-glasses upon growing all-inorganic lead halide perovskites within three different types of inorganic oxide glasses. When a silver metaphosphate glass matrix is used it is revealed that the low glass transition temperature of the phosphate glass limits significantly the temperature range of the required post-melting annealing treatment, while the lead salt precursors react with the phosphate entities of the network destroying the stoichiometry of the PNCs. As a result the formation of PNCs is hindered. As a consequence, a double network former borophosphate glass was employed as a suitable host. While annealing treatments at higher temperature were facilitated in this case, it is found that the high silver content becomes an obstacle for the perovskite formation. In view of these findings, cesium lead bromide (CsPbBr3) and cesium lead iodide (CsPbI3) composite perovskite borate glasses were synthesized and found to be suitable hosts. Indeed, such composite glasses exhibit interesting photoluminescence properties that are compared with those of PNCs outside the glass matrix.

The Reactivity of CsPbBr3 Nanocrystals toward Acid/Base Ligands.

The interaction of lead bromide perovskite nanocrystals with charged ligands, such as salts, zwitterions, or acid–base pairs, has been extensively documented over the past few years. On the other hand, little is known about the reactivity of perovskite nanocrystals toward neutral ligands. To fill this gap, in this work we study the interaction of CsPbBr3 nanocrystals passivated with didodecyldimethylammonium bromide (DDABr) toward a series of exogenous acid/base ligands using a combined computational and experimental approach. Our analysis indicates that DDABr-capped nanocrystals are inert toward most ligands, except for carboxylic, phosphonic, and sulfonic acids. In agreement with the calculations, our experimental results indicate that the higher the acidity of the ligands employed in the treatment, the more etching is observed. In detail, dodecylbenzenesulfonic acid (pKa = −1.8) is found to etch the nanocrystals, causing their complete degradation. On the other hand, oleic and oleylphosphonic acids (pKa 9.9 and 2, respectively) interact with surface-bound DDA molecules, causing their displacement as DDABr in various amounts, which can be as high as 40% (achieved with oleylphosphonic acid). Despite the stripping of DDA ligands, the optical properties of the nanocrystals, as well as structure and morphology, remain substantially unaffected, empirically demonstrating the defect tolerance characterizing such materials. Our study provides not only a clear overview on the interaction between perovskite nanocrystals and neutral ligands but also presents an effective ligand stripping strategy.

Low temperature synthesis of ultra-green luminescent colloidal FAPbBr3 perovskite nanocrystals

According to the updated recommendation for displays standard (Rec. 2020), ultrapure green emitters with a narrow emission (below 25 nm) in the 525–535 nm spectral range are desired. However, finding an emitter material that can meet such requirements, is still challenging. To this purpose, organic–inorganic halide perovskites nanocrystals have been considered as promising high-color purity light emitters at a lower cost, that overcome the issues associated with conventional emitters. Herein, to reach these standards simultaneously, we have synthesized Formamidinium lead bromide perovskite nanocrystals (NCs) at room temperature by ligand-assisted reprecipitation (LARP). The obtained FAPbBr3 NCs coated with oleic acid and oleylamine show an average size of about 20 nm. FAPbBr3 NCs dispersions in hexane exhibited bright photoluminescence with a high quantum yield (74%). The color coordinates on CIE 1931 are (0.2, 0.75), with a corresponding strong green emission at 533 nm. The emission is characterized by an ultranarrow full width at half-maximum (FWHM = 22 nm), and long radiative lifetimes (≈82 ns). The synthesized FAPbBr3 NCs present ideal features toward solution-processable ultrapure green emitters.

Corrigendum: Cesium Lead Bromide Perovskite Nanocrystals as a Simple and Portable Spectrochemical Probe for Rapid Detection of Chlorides

Corrigendum: Cesium Lead Bromide Perovskite Nanocrystals as a Simple and Portable Spectrochemical Probe for Rapid Detection of Chlorides

Effect of alkali metal nitrate treatment on the optical properties of CsPbBr3 nanocrystal films

Colloidal cesium lead bromide (CsPbBr3) perovskite nanocrystals (NCs) are fabricated as densely packed thin films using doctor blade method through a layer-by-layer assembly approach. It is found that the optical properties of the CsPbBr3 NC films are significantly improved after a ligand exchange of oleic acid (OA) and oleylamine (OAm) by sodium and potassium nitrate in ethyl acetate. Ligand-induced surface defects are passivated by the sodium and potassium cations and nitrate, which leads to the improvement in photoluminescence (PL) and life-time properties. Compared with pristine OAm-OA capped CsPbBr3 NC film, Alkali-metal nitrate salts treated films are showing higher PL intensity and longer carrier-lifetime, evidencing their potential use to achieve defect-free inorganic perovskite NC films.

Cesium Lead Bromide Perovskite Nanocrystals as a Simple and Portable Spectrochemical Probe for Rapid Detection of Chlorides

AbstractThe wide spectral tunability of CsPbBr3 perovskite nanocrystals (NCs) via instantaneous and facile anion exchange, make them a suitable candidate for chloride detection. Rapid anion‐exchange processes between CsPbBr3 perovskite NCs and different chloride solutions were carried out in ambient conditions. The resultant anion‐exchanged CsPbCl3‐xBrx NCs preserved the structural properties and exhibited a remarkable blue‐shift in photoluminescence spectra. This form a basis for detection of chloride ions in water. This has been applied with the limit of detection upto 100 μM. The detection strategies were not only limited to the direct addition of chloride solutions to NCs, but also showed a visual colour change under UV light when the chloride solution is drop‐casted on CsPbBr3 films that are deposited on glass substrates. Furthermore, the detection strategy is established by drop‐casting CsPbBr3 NCs onto paper strips that are pre‐soaked in chloride solutions. A considerable blue‐shift in fluorimetry proves them to be an excellent sensing medium as practical spectrochemical probes for on‐site detection of chlorides. Based on this, a colour chart and selectivity chart to access the presence of chlorides and their concentration is demonstrated here.

Monodisperse caesium lead bromide perovskite nanocrystals (NCs) CsPbBr3 with bright and stable green photoluminescence for application in light emitting devices

Monodisperse caesium lead bromide perovskite nanocrystals (NCs) CsPbBr₃ with bright and stable green photoluminescence for application in light emitting devices

Inorganic Ruddlesden-Popper Faults in Cesium Lead Bromide Perovskite Nanocrystals for Enhanced Optoelectronic Performance.

While the layered hybrid Ruddlesden-Popper (RP) halide perovskites have already established themselves as the frontrunners among the candidates in optoelectronics, their all-inorganic counterparts remain least explored in the RP-type perovskite family. Herein, we study and compare the optoelectronic properties of all-inorganic CsPbBr3 perovskite nanocrystals (PNCs) with and without RP planar faults. We find that the RP-CsPbBr3 PNCs possess both higher exciton binding energy and longer exciton lifetimes. The former is ascribed to a quantum confinement effect in the PNCs induced by the RP faults. The latter is attributed to a spatial electron-hole separation across the RP faults. A striking difference is found in the up-conversion photoluminescence response in the two types of CsPbBr3 PNCs. For the first time, all-inorganic RP-CsPbBr3 PNCs are tested in light-emitting devices and shown to significantly outperform the non-RP CsPbBr3 PNCs.

Highly stable cesium lead bromide perovskite nanocrystals for ultra-sensitive and selective latent fingerprint detection

Latent fingerprints (LFPs) are one of the most important forms of evidence in crime scenes due to the uniqueness and permanence of the friction ridges in fingerprints. Therefore, an efficient method to detect LFPs is crucial in forensic science. However, there remain several challenges with traditional detection strategies including low sensitivity, low contrast, high background, and complicated processing steps. In order to overcome these drawbacks, we present an approach for developing latent fingerprints using stabilized CsPbBr3 perovskite nanocrystals (NCs) as solid-state nanopowders. We demonstrate the superior optical stability of CsPbBr3 NCs with respect to absorption, photoluminescence (PL), and fluorescence lifetime. We then used these highly stable, fluorescent CsPbBr3 NCs as a powder dusting material to develop LFPs on diverse surfaces. The stable optical properties and hydrophobic surface of the CsPbBr3 NC nanopowder permitted high resolution images from which unique features of friction ridge arrangements with first, second, and third-level LFP details can be obtained within minutes.