Lead Bromide Perovskite Nanocrystals Research Articles

CsPbBr3 perovskite nanocrystals-based portable testing device for on-site detection of chloride ions from wastewater

The detrimental effects of chloride (Cl−) ions on industrial wastewater necessitate the in-situ monitoring of Cl−, which is challenging due to the limited availability of field-applicable analytical methodologies. Herein, a novel and compact apparatus (CPB-FC-Cl) was developed for the precise quantification of Cl− in wastewater. This innovative system utilizes the rapid halide exchange of cesium lead bromide (CsPbBr3) perovskite nanocrystals (NCs) with Cl−, a process marked by a pronounced wavelength blueshift and a vivid fluorescence transition from green to blue. The software in the CPB-FC-Cl system automatically identified the fluorescence emission peaks and displayed the Cl− concentration values on the user interface. The detection experiments conducted on actual hydrochloric acid wastewater confirmed the device’s ability to accurately measure Cl− concentrations within 5 min, achieving an accuracy of 98.98 %. The CPB-FC-Cl system exhibited high selectivity in the presence of various coexisting substances in hydrochloric acid wastewater, and its resistance to potential interferences supports its suitability for precise Cl− quantification. The stability of the CPB-FC-Cl system showed an average detection accuracy of 98.96 % over multiple cycles, which underscores its robustness for long-term monitoring applications.

Cesium lead bromide perovskite nanocrystals as fluorescent taggants for detecting fluid leaks

Fluorescence tagging represents a low cost, fast, and reliable method for leak detection in the chemical industry. Here, the use of halide perovskites as fluorescent taggants is demonstrated to detect piping leakages. To this end, cesium lead bromide (CsPbBr3) nanocrystals were synthesized at room temperature and dissolved in silicon oil as a green luminophore (530 ± 5 nm). The resulting system had a photoluminescence quantum yield of 48 ± 2 % while retaining key optical properties (emission linewidth and lifetime) over the timescale required for typical leak detection (2–30 minutes), even under strongly acidic/basic conditions (pH 1–13) and high pressures (up to 7 atm). Crucially, the operating dose of CsPbBr3 required for leak detection is an order of magnitude lower than those used for typical commercial fluorescent taggants (0.03 versus 0.003 oz mL−1). These results strongly suggest the great potential of halide perovskites towards industrial leak detection applications.

The role of photonic crystal based architectures on tailoring the laser induced fluorescence from green emitting cesium lead bromide nanocrystals

Researchers have long been fascinated by fluorescence and its potential to be boosted as it unlocks a treasure trove of promising applications. In this context, this experimental study investigates the amplification of laser induced fluorescence (LIF) emission from cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNC) using two distinct all-polymer photonic crystal (PC) architectures made of poly 9-vinyl carbazole (PVK) and cellulose acetate (CA) as high and low refractive index (RI) layers, respectively. First structure is a photonic crystal micro cavity (PCMC) where PNC incorporated PVK (PNC:PVK) polymer matrix forms the defect layer sandwiched between two similar PCs. In the second structure, PNC:PVK composite itself functions as high RI layers within the PC. These two designs exploit different mechanisms to achieve fluorescence enhancement. The findings demonstrate the promise of simple, solution processed polymer PCs on applications demanding intensified fluorescence output and pave way to the development of flexible photonic devices capable of manipulating light emission.

Biexciton Emission in CsPbBr3 Nanocrystals: Polar Facet Matters.

The metal halide perovskite nanocrystals exhibit a remarkable tolerance to midgap defect states, resulting in high photoluminescence quantum yields. However, the potential of these nanocrystals for applications in display devices is hindered by the suppression of biexcitonic emission due to various Auger recombination processes. By adopting single-particle photoluminescence spectroscopy, herein, we establish that the biexcitonic quantum efficiency increases with the increase in the number of facets on cesium lead bromide perovskite nanocrystals, progressing from cube to rhombic dodecahedron to rhombicuboctahedron nanostructures. The observed enhancement is attributed mainly to an increase in their surface polarity as the number of facets increases, which reduces the Coulomb interaction of charge carriers, thereby suppressing Auger recombination. Moreover, Auger recombination rate constants obtained from the time-gated photon correlation studies exhibited a discernible decrease as the number of facets increased. These findings underscore the significance of facet engineering in fine-tuning biexciton emission in metal halide perovskite nanocrystals.

CsPbBr3 NCs Confined and In Situ Grown in ZIF-8: A Stable, Sensitive, Reliable Fluorescent Sensor for Evaluating the Acid Value of Edible Oils.

Rapidly and sensitively evaluating the acid value (AV) of edible oils is significant to ensuring food quality and safety. Cesium lead bromide perovskite nanocrystals (CsPbBr3 NCs) are an effective candidate for AV detection; however, their instability restricts wide applications. Herein, CsPbBr3@ZIF-8 was prepared by confining and growing CsPbBr3 NCs in situ into zeolitic imidazolate framework-8 (ZIF-8) to improve the stability, and a fluorescence sensor was established to evaluate the AV of edible oils. The results present that CsPbBr3 NCs (below 5 nm) with excellent optical properties were confined and grown in situ in micropores and mesopores of ZIF-8. Meanwhile, CsPbBr3@ZIF-8 had better long-term storage, ultraviolet-irradiation, and water-exposure stabilities, compared with CsPbBr3 NCs. Given the fact that free fatty acids (the major contributor of AV) decrease the fluorescence of CsPbBr3 NCs, the fluorescence intensities of CsPbBr3@ZIF-8 were negative-linearly related to oil AV (R2 = 0.9902) in 0.04-6.00 mg of KOH/g with a 0.06 mg of KOH/g limit of detection. Besides, the practical AV recovery was 92-101% with an average relative standard deviation of 2%. Furthermore, the detection time was 20 min. The response mechanism revealed that free fatty acids could remove surface ligands and increase surface defects to prompt the aggregation of CsPbBr3 NCs and the formation of lattice fringe dislocations, inducing a decrease in the fluorescence. Thus, a stable, sensitive, reliable sensor was established to evaluate the AV of edible oils.

Fine-Tuning Crystal Structures of Lead Bromide Perovskite Nanocrystals through Trace Cadmium(II) Doping for Efficient Color-Saturated Green LEDs.

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.

Fine‐Tuning Crystal Structures of Lead Bromide Perovskite Nanocrystals through Trace Cadmium(II) Doping for Efficient Color‐Saturated Green LEDs

AbstractDecreasing 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.

Surface-Engineered Cesium Lead Bromide Perovskite Nanocrystals for Enabling Photoreduction Activity.

In recent years, colloidal lead halide perovskite (LHP) nanocrystals (NCs) have exhibited such intriguing light absorption properties to be contemplated as promising candidates for photocatalytic conversions. However, for effective photocatalysis, the light harvesting system needs to be stable under the reaction conditions propaedeutic to a specific transformation. Unlike photoinduced oxidative reaction pathways, photoreductions with LHP NCs are challenging due to their scarce compatibility with common hole scavengers like amines and alcohols. In this contribution, it is investigated the potential of CsPbBr3 NCs protected by a suitably engineered bidentate ligand for the photoreduction of quinone species. Using an in situ approach for the construction of the passivating agent and a halide excess environment, quantum-confined nanocubes (average edge length = 6.0 ± 0.8 nm) are obtained with a low ligand density (1.73 ligand/nm2) at the NC surface. The bifunctional adhesion of the engineered ligand boosts the colloidal stability of the corresponding NCs, preserving their optical properties also in the presence of an amine excess. Despite their relatively short exciton lifetime (τAV = 3.7 ± 0.2 ns), these NCs show an efficient fluorescence quenching in the presence of the selected electron accepting quinones (1,4-naphthoquinone, 9,10-phenanthrenequinone, and 9,10-anthraquinone). All of these aspects demonstrate the suitability of the NCs for an efficient photoreduction of 1,4-naphthoquinone to 1,4-dihydroxynaphthalene in the presence of triethylamine as a hole scavenger. This chemical transformation is impracticable with conventionally passivated LHP NCs, thereby highlighting the potential of the surface functionalization in this class of nanomaterials for exploring new photoinduced reactivities.

Insight into the Structures and Photophysics of Zn-Alloyed Lead Bromide Perovskite Nanocrystals Synthesized by a Post-Ion-Exchange Method and a One-Pot Hot Injection Method

Insight into the Structures and Photophysics of Zn-Alloyed Lead Bromide Perovskite Nanocrystals Synthesized by a Post-Ion-Exchange Method and a One-Pot Hot Injection Method

Cesium lead bromide perovskite nanocrystals synthesized via supersaturated recrystallization at room temperature: comparison of one-step and two-step processes.

Over more than a decade, lead halide perovskites (LHPs) have been popular as a next-generation semiconductor for optoelectronics. Later, all-inorganic CsPbX3 (X = Cl, Br, and I) nanocrystals (NCs) were synthesized via supersaturated recrystallization (SR) at room temperature (RT). However, compared to the hot injection (HI) method, the formation mechanism of NCs via SR-RT has not been well studied. Hence, this study will contribute to elucidating SR-RT based on the LaMer model and Hansen solubility parameter. Herein, we also demonstrate the entropy-driven mixing between two dissimilar polar-nonpolar (DMF-toluene) solvents. Next, we find that, in a poor solvent (toluene ≫ DMF in volume), ∼60 nm sized CsPbBr3 NCs were synthesized in one step, whereas in a marginal solvent (toluene ≈ DMF), ∼3.5 nm sized NCs were synthesized in two steps, indicating the importance of solvent polarity, specifically the 'solubility parameter'. In addition, in the presence of a CuBr2 additive, high-quality cubic NCs (with ∼3.8 nm and ∼21.4 nm edge sizes) were synthesized. Hence, through this study, we present a 'solubility parameter-based nanocrystal-size control model' for SR-RT processes.

Effect of the A-Site Cation on the Biexciton Dynamics in Lead Bromide Perovskite Nanocrystals

Effect of the A-Site Cation on the Biexciton Dynamics in Lead Bromide Perovskite Nanocrystals

Stability and Degradation in Lead Halide Perovskite Nanocrystals via Regulation of Lattice Strain.

It is still quite challenging to achieve high-performance and stable blue perovskite materials due to their instability and degradation. The lattice strain provides an important pathway to investigate the degradation process. In this article, the lattice strain in perovskite nanocrystals was regulated by the ratio of Cs+, EA+, and Rb+ cations with different sizes. Their electrical structure, formation energy, and ion migration activation energy were calculated with the density functional theory (DFT) method. The luminescence properties and stability of blue lead bromide perovskite nanocrystals were analyzed with spectra regulation from 516 to 472 nm. It was demonstrated that the lattice strain plays an important role in the luminescence performance and degradation process of perovskite materials. The study provides the positive correlation between lattice strain and degradation as well as luminescence properties in lead halide perovskite materials, which is of great importance in uncovering their degradation mechanism and developing stable and high-performance blue perovskite materials.

Understanding the ligand-assisted reprecipitation of CsPbBr3 nanocrystals via high-throughput robotic synthesis approach

•High-throughput automated experimental workflow for LARP-PNC synthesis is employed •Effects of chemical and processing parameters on PNC functionalities are explored •SHAP, a machine learning method, assesses the impact of synthesis parameters •Ligand diffusion during reaction determines the functionalities of PNCs Inorganic cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNCs) have shown promise in optoelectronic applications. A simpler method of synthesizing high-quality PNCs is the ligand-assisted reprecipitation (LARP) method, but it is susceptible to instability. This study used a high-throughput automated experimental platform to explore the growth behaviors and colloidal stability of LARP-synthesized PNCs. The influence of ligands on particle growth and functionalities was systematically explored using two distinctive acid-base pairs. The study found that short-chain ligands cannot make functional PNCs with the desired sizes and shapes, whereas long-chain ligands provide homogeneous and stable PNCs. The study also found that excessive amines or polar antisolvents can cause PNCs to transform into a Cs-rich non-perovskite structure with poorer emission functionalities and larger size distributions. The diffusion of ligands in a reaction system is crucial in determining the structures and functionalities of the PNCs. This study provides detailed guidance on synthesis routes for desired PNCs. Inorganic cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNCs) have shown promise in optoelectronic applications. A simpler method of synthesizing high-quality PNCs is the ligand-assisted reprecipitation (LARP) method, but it is susceptible to instability. This study used a high-throughput automated experimental platform to explore the growth behaviors and colloidal stability of LARP-synthesized PNCs. The influence of ligands on particle growth and functionalities was systematically explored using two distinctive acid-base pairs. The study found that short-chain ligands cannot make functional PNCs with the desired sizes and shapes, whereas long-chain ligands provide homogeneous and stable PNCs. The study also found that excessive amines or polar antisolvents can cause PNCs to transform into a Cs-rich non-perovskite structure with poorer emission functionalities and larger size distributions. The diffusion of ligands in a reaction system is crucial in determining the structures and functionalities of the PNCs. This study provides detailed guidance on synthesis routes for desired PNCs.

Charge Transfer in Amine-Free CsPbBr3 Perovskite Nanocrystals and Organic Hole-Acceptor Hybrid Structures

Outstanding optoelectronic properties of cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNCs) are recognized in various photonic devices. The surface chemistry of PNCs determines the excited states of PNCs, and their interactions with charge drive redox-active molecules. Here, we have investigated the potential difference between the surface modification of different CsPbBr3-based PNCs (amine-free and amine-based) with the hole-accepting organic molecule, i.e., 7,7-diethyl-5,7-dihydroindeno[2,1-b] carbazole (SPS-IND-Cbz). We have evaluated photoinduced hole transfer (PHT) with the steady-state photoluminescence and lifetime decay curves. Excitingly, the resulting PHT in amine-free CsPbBr3 PNC was nearly twice that of the amine-based CsPbBr3 PNC. Further, we have studied the photocurrent density of amine-free CsPbBr3 PNCs in the newly introduced organic molecule (SPS-IND-Cbz), enhancing the photocurrent responsivity, which could open a promising perspective for implementing these fascinating materials in various photonic strategies.

Correlation between Single-Photon Emission and Size of Cesium Lead Bromide Perovskite Nanocrystals.

Emission photon statistics of semiconductor nanocrystal quantum dots (QDs), including lead halide perovskite nanocrystals (PNCs), are important fundamental and practical optical properties. Single QDs exhibit high-probability single-photon emission owing to the efficient Auger recombination between generated excitons. Because the recombination rate depends on QD size, single-photon emission probability should be size-dependent. Previous studies have researched QDs smaller than their exciton Bohr diameters (twice the Bohr radius of excitons). Here, we investigated the relationship between the single-photon emission behavior and size of CsPbBr3 PNCs to elucidate their size threshold. Simultaneous single-nanocrystal spectroscopy and atomic force microscopy observations on single PNCs with approximately 5-25 nm edge length showed that those smaller than approximately 10 nm, which had size-dependent photoluminescence (PL) spectral shifts, exhibited high-probability single-photon emissions, which decreased linearly with PNC volume. Novel single-photon emission, size, and PL peak correlations of PNCs are important for understanding the relationship between single-photon emission and quantum confinement.

Optical and photoelectrical properties of low-concentration-Mn-doped CsPbBr3 nanocrystals

Doping of cesium lead bromide (CsPbBr3) perovskite nanocrystals offers effective control of their optical and optoelectrical properties, leading to possibilities of several new applications. Herein, cesium lead bromide perovskite nanocrystals are synthesized with doping of a low concentration of manganese (Mn) into the perovskite lattice using manganese (II) chloride (MnCl2) as a precursor. The shift in X-ray diffraction peaks toward higher angles indicates that manganese as a dopant is present inside the cesium lead bromide lattice. A change in the manganese (II) chloride precursor concentration from 5 to 10 mmol results in an increment in the atomic percentage of manganese from 0.3 to 0.5% in the cesium lead bromide crystal. Doping of a low concentration of manganese (0.3 at.%) into cesium lead bromide results in enhancement of green emission, while doping with a higher concentration of manganese (0.5 at.%) results in blue emission. The band gap of cesium lead bromide nanocrystals increases from 2.31 to 2.53 eV with an increase in the concentration of manganese. The dark and photoelectrical conductivity of cesium lead bromide nanocrystals is improved in the case of doping with a low concentration (0.3 at.%) of manganese. The ratio of photocurrent against dark current is found to be ∼182 in manganese-doped cesium lead bromide crystal film as compared with ∼101 for undoped cesium lead bromide crystal film. Doping with a low concentration of manganese improves the overall electrical and photoelectrical conductivity of cesium lead bromide perovskite nanocrystals.

Water-induced nucleation growth kinetics enhancement of cesium lead bromide perovskite nanocrystals

Water-induced nucleation growth kinetics enhancement of cesium lead bromide perovskite nanocrystals

Slower Auger Recombination in 12-Faceted Dodecahedron CsPbBr3 Nanocrystals.

Over the past two decades, intensive research efforts have been devoted to suppressions of Auger recombination in metal-chalcogenide and perovskite nanocrystals (PNCs) for the application of photovoltaics and light emitting devices (LEDs). Here, we have explored dodecahedron cesium lead bromide perovskite nanocrystals (DNCs), which show slower Auger recombination time compared to hexahedron nanocrystals (HNCs). We investigate many-body interactions that are manifested under high excitation flux density in both NCs using ultrafast spectroscopic pump-probe measurements. We demonstrate that the Auger recombination rate due to multiexciton recombinations are lower in DNCs than in HNCs. At low and intermediate excitation density, the majority of carriers recombine through biexcitonic recombination. However, at high excitation density (>1018 cm-3) a higher number of many-body Auger process dominates over biexcitonic recombination. Compared to HNCs, high PLQY and slower Auger recombinations in DNCs are likely to be significant for the fabrication of highly efficient perovskite-based photonics and LEDs.

Photostability of amine-free CsPbBr3 perovskite nanocrystals under continuous UV illumination

In this work, we verified that light induces a dynamic equilibrium between ligands and the inorganic surface in amine-free perovskite nanocrystals, and we demonstrated that oleylphosphate ligands can improve the photostability of cesium lead bromide perovskite nanocrystals.

Photo-induced structural and optical changes of CsPbBr3 perovskite nanocrystals in glasses

Cesium lead halide perovskite nanocrystals have particular optoelectronic properties and important applications in various fields. Embedding cesium lead halide perovskite nanocrystals into glass matrices have improved their thermal and chemical stabilities. However, these cesium lead halide perovskite nanocrystals in glasses are still sensitive to intense light irradiation, limiting their wide applications. In this work, fs laser irradiation on the structural and optical properties of cesium lead bromide (CsPbBr3) perovskite nanocrystals (PNCs) is investigated. It turns out that fs laser irradiation does not change the structural skeletons and band gap energies of CsPbBr3 PNCs in glasses, but induces surface Br vacancies. In-situ transient absorption spectral analysis reveals one <10 ps trapping process of photo-generated carriers after fs laser irradiation, and confirms that Br vacancies are induced by Br migration driven by photo-generated carriers. In addition, CsPbBr3 PNCs with high PL QY in glasses through Br passivation can be more easily damaged by fs laser, making it difficult to achieve stable stimulated emission towards laser application. These results shine light on the effect of halogen contents on the photo-stability of cesium lead halide PNCs and the regulation of cesium lead halide PNCs embedded glasses for photo-electronic applications.