CsPbBr3 Nanocrystals Research Articles

Electron-donating functional groups strengthen ligand-induced chiral imprinting on CsPbBr3 quantum dots

Chiral perovskite nanoparticles and films are promising for integration in emerging spintronic and optoelectronic technologies, yet few design rules exist to guide the development of chiral material properties. The chemical space of potential building blocks for these nanostructures is vast, and the mechanisms through which organic ligands can impart chirality to the inorganic perovskite lattice are not well understood. In this work, we investigate how the properties of chiral ammonium ligands, the most common organic ligand type used with perovskites, affect the circular dichroism of strongly quantum confined CsPbBr3 nanocrystals. We show that aromatic ammonium ligands with stronger electron-donating groups lead to higher-intensity circular dichroism associated with the lowest-energy excitonic transition of the perovskite nanocrystal. We argue that this behavior is best explained by a modulation of the exciton wavefunction overlap between the nanocrystal and the organic ligand, as the functional groups on the ligand can shift electron density toward the organic species-perovskite lattice interface to increase the imprinting.

Photoluminescence and photovoltaic properties of cesium lead bromide nanocrystals with linoleic acid ligand

Cesium lead bromide (CsPbBr3) nanocrystals (NCs) were synthesized using the ligand-assisted reprecipitation (LARP) method, with linoleic acid (LA) and oleylamine (OlAm) as ligands. The crystal structures of the samples depend on the ligand used in the synthesis. Sample-1, with LA-OlAm as the ligand, showed an orthorhombic crystal structure, whereas Sample-2, with OlAm only, showed a tetragonal crystal structure. These samples exhibited slightly different photoluminescence (PL) characteristics, where the PL peak of Sample-1 appeared at 521.4 nm, whereas the PL peak of Sample-2 appeared at 524.1 nm. Sample-1 showed brighter PL than that of Sample-2. These differences are strongly related to their crystal structures and degree of crystallization, which is also evident from the differences in the chemical states of the Br and Pb ions on the NCs surface, as depicted by the X-Ray Photoelectron Spectroscopy (XPS) spectra. In addition, despite exhibiting PL characteristics, these CsPbBr3 NCs also exhibit photovoltaic properties.

Fabrication of water-resistant fluorescent ink using the near-unity photoluminescence quantum yield of CsPbBr3 doped with NiBr2.

Doping with transition and alkaline earth metal ions into all-inorganic perovskite nanocrystals (NCs) has attracted attention recently for tuning the photoluminescence quantum yield (PLQY). We report on the hot injection synthesis of nickel ion-doped CsPbBr3 NCs with near-unity PLQYs. Nickel ions were successfully incorporated into the octahedral environment of CsPbBr3 NCs, replacing the lead ions. The introduction of nickel ions into CsPbBr3 NCs substantially eliminates intrinsic defects and halide vacancies for improved structural order and near-unity PLQYs. Benefiting from these unique properties, nickel ion-doped CsPbBr3 NCs were dispersed in a polymer to prepare an efficient fluorescent ink. The fluorescent ink shows excellent thermal and water stability under harsh environmental conditions. Moreover, the usefulness of the fluorescent ink for security purposes was demonstrated by designing and recognizing a fluorescent QR code. This study reveals that doped CsPbBr3 NCs can be used to prepare efficient water-resistant fluorescent ink for anti-counterfeiting applications, widening the usefulness of doped all-inorganic perovskite NCs.

Influence of arylalkyl amines on the formation of hybrid CsPbBr3 nanocrystals via a modified LARP method.

Perovskite nanocrystals have attracted much attention in the last ten years due to their different applications, especially in the photovoltaic domain and LED performance. In this large family of perovskite nanocrystals, CsPbBr3 nanocrystals are attractive nanomaterials because they are good candidates for obtaining green emissions and exploring new synthesis routes. In this context, controlling the nanometric scale's morphology, particularly the size and monodispersity, is fundamental for exploring their photophysical properties and final applications. Currently, the nanometric size of nanocrystals is ensured by the presence of oleic acid and oleylamine molecules, in using Hot Injection (HI) or ligand-assisted reprecipitation (LARP) methods. If oleic acid plays a fundamental role, oleylamine can be easily substituted by other amino molecules, opening the way for the functionalization of CsPbBr3 nanocrystals and the obtention of new hybrid perovskite nanocrystal families. In this article, we describe the synthesis, by soft chemistry, of a new family of hybrid organic-inorganic CsPbBr3 nanocrystals, functionalized by aryl-alkylamine (AAA) molecules, through the modified LARP method. We highlight the mechanism for cutting submicron crystals into nanocrystals, using aryl-alkylamine molecules like scissors. The impact of these amino molecules on the final nanocrystals leads to different nanocrystal morphologies (nanocubes, nanosheets, or nanorods) and structures (monoclinic, rhombohedral, or tetragonal). In addition, this modified LARP method highlights, under certain experimental conditions, an unexpected formation of PbO ribbons.

Surfactant-tail control of CsPbBr3 nanocrystal morphology.

CsPbBr3 nanocrystals (NCs) are promising optoelectronic and catalytic materials. Manipulating their morphology can improve their properties and stability. In this work, an alkene-derived zwitterionic ligand was used to control the morphology of CsPbBr3 NCs to yield the highly unusual rhombicuboctahedron morphology, showcasing the first example of a surfactant-tail controlled growth.

Broadband photodetectors from silane-passivated CsPbBr3 nanocrystals by ultrasound-mediated synthesis.

Perovskite nanocrystals have excellent optical properties but suffer from environmental instability and production up-scaling which limit their commercial application. Here, we report the gram-scale ultrasound-mediated synthesis of silane passivated CsPbBr3 nanocrystals using (3-aminopropyl) triethoxysilane (APTS) as the primary surface ligand surface. The surface engineering endowed the CsPbBr3@SiOR NCs with extended environmental stability, a narrow emission bandwidth and a high photoluminescence quantum yield (PLQY > 75%). Thanks to these excellent optical properties, high-efficiency lateral and vertical photodetectors were fabricated. In particular, the layered vertical photodiode composed of ITO/Ga2O3/CsPbBr3/Au exhibited a broadband photoresponse from 350-700 nm with a responsivity peaking at 44.5.1 A W-1 and specific detectivity above 1013 Jones when illuminated at 470 nm wavelength and biased at +5 V. These results correspond to the best-in-class performance perovskite nanocrystal PD and confirm the extraordinary potential of CsPbBr3@SiOR for the development of efficient optoelectronic devices.

The more the merrier: optimizing monomer concentration for supersaturation controlled synthesis of stable ultra-small CsPbBr3 nanocrystals for blue emission.

Synthesis of strongly quantum confined and emissive CsPbBr3 perovskite nanocrystals with sizes <4 nm has proven challenging owing to fast nucleation and rapid growth. In this work, ultra-small blue-emitting (∼461 nm) CsPbBr3 nanocrystals with an average particle size of 3.2 nm are synthesized via a high-temperature (170 °C) colloidal approach by controlling the supersaturation reaction conditions. Our approach yielded stable nanocrystals with uniform size, shape, and excellent color purity, making them promising for blue light emitting diode (LED) applications.

Insights into interfacial mechanisms: CsPbBr3 nanocrystals as sustainable photocatalysts for primary amine oxidation.

CsPbBr3 nanocrystals (NCs) employed as a photocatalyst resulted in efficient benzylamine oxidation under oxygen atmosphere. Improved reaction yields stem from favorable -NH2 functional group interactions on the NC surface, while additional interactions with -OMe or -SMe functional groups post-product formation result in lower yields. These insights into interfacial interactions and mechanistic aspects advance sustainable chemical transformations through cost-effective and recyclable CsPbBr3 NC-catalyzed primary amine oxidation.

Cathodoluminescence spectral and lifetime mapping of Cs4PbBr6: fast lifetime and its scintillator application

Highly efficient green emission of Cs4PbBr6 has been attributed to intermediate states formed by embedded CsPbBr3 nanocrystals or defects. However, direct experimental confirmation of the presence of such nano-emitters is not straightforward and the emission mechanism remains elusive. By using cathodoluminescence (CL) imaging with a high spatial resolution, we demonstrate that CsPbBr3 nanocrystals within the Cs4PbBr6 matrix contribute to the green emission, exhibiting optical behavior distinct from the matrix. Additionally, we explore its potential as an electron beam scintillator, given its high CL intensity and exceptionally short lifetime.

Enhanced stability of CsPbBr3 nanocrystals through Al2O3 and polymer coating.

Lead halide perovskite nanocrystals have emerged as a promising candidate for next-generation display applications due to their attractive optical properties and low-cost production. However, the environmental stability of perovskite remains a major challenge, hindering their practical applications and scalability for commercialization. In this study, we present an effective method to enhance the stability of CsPbBr3 nanocrystals by coating them with a combination of Al2O3 and a polymer. The unique double protection structure significantly improves their resistance to moisture, heat, and polar solvents. It is worth noting that compared with the ordinary CsPbBr3 nanocrystals, the modified nanocrystals have better stability and higher luminous intensity. After soaking in water for 360 hours, the modified nanocrystals retained 85% of their initial luminous intensity. Under optimal conditions, the luminous intensity of modified nanocrystals increased by 36%. Furthermore, the thermal stability and organic solvent resistance of the nanocrystals are improved compared with the nanocrystals uncoated with Al2O3. The synthesized white light emitting diode using the modified PNCs achieves a color gamut coverage rate of 129% under standard NTSC, and 95% under standard Rec.2020, indicating its potential for future display applications. This research presents a promising approach for the development of stable perovskite nanocrystals with enhanced performance in various optoelectronic devices.

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.

A photoelectrochemical capacitor using polyoxometalates coupled with semiconductor nanocrystals as the photosensitizer.

Solar energy storage technology ensures a sustainable and reliable energy supply. Herein, we show that electrons generated in semiconductor nanocrystals (NCs) of CsPbBr3 by visible light excitation can be stored in polyoxometalates (POMs) of W10O32, and extracted as an electric current using a photoelectrochemical cell.

Prevention of ion migration in lead halide perovskites upon plugging the anion vacancies with PbSe islands.

To circumvent the issue of halide ion exchange in perovskites, we have decorated CsPbBr3 and CsPbI3 nanocrystals with different sized PbSe nanoparticles and demonstrated that it effectively prevents anion exchange reaction in CsPbBr3/CsPbI3 nanoheterostructures (NHSs) as a consequence of halide vacancy passivation by the more covalent selenide anion.

Harnessing laser technology to create stable metal halide perovskite-rGO conjugates as promising electrodes for Zn-ion capacitors.

We report that the direct conjugation of metal halide perovskite nanocrystals on rGO sheets can provide high performance and stable electrodes for Zn-ion capacitors. It is the first time that metal halide nanocrystals have been used to enhance the energy storage of 2D materials in capacitors by introducing an additional pseudocapacitance mechanism. In particular, we present a simple, rapid and room temperature laser-induced method to anchor CsPbBr3 nanocrystals on rGO sheets without affecting the initial morphology and crystal structure of the two components. The flexible and high surface area of the rGO sheets enables the conjugation of individual metal halide perovskite nanocrystals, giving rise to new synergetic functionalities. As a result, the specific capacitance of the perovskite-rGO conjugated electrodes can be enhanced by 178- and 152-times compared to those of the plain rGO and perovskite electrodes respectively.

Analytical detection of the bioactive molecules dopamine, thyroxine, hydrogen peroxide, and glucose using CsPbBr3 perovskite nanocrystals

Qualitative and quantitative detection of biologically important molecules such as dopamine, thyroxine, hydrogen peroxide, and glucose, using CsPbBr3 nanocrystals coated paper/glass substrates are discussed.

Morphology, luminescence and the gravity sedimentation effect of flexible and highly stable CsPbBr3 nanocrystal patterns by the inkjet printing method

Fine and well-defined CsPbBr3 nanocrystals are in situ crystallized within the flexible and transparent PVP matrix, displaying excellent ambient stability.

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.

CsPbBr3 nanocrystals as electron and ion “Reservoirs” to induce energy transfer and grain reconstruction for efficient carbon-based inorganic perovskite solar cells

Electron cloud density around the functional group of Lewis-base molecule (passivator) highly determines the interaction strength with undercoordinated Pb2+ in perovskite film. With the aim to maximize this scenario, herein, we fabricate a thermally-activated delayed fluorescence molecule (3,4,5,6-tetrakis(3,6-diphenylcarbazol-9-yl)-1,2-dicyanobenzene, 4CzPN-Ph) bound CsPbBr3 nanocrystal (NC) to heal the defective perovskite surface. Because of the suitable energy alignment, there is a Förster or Dexter triplet energy transfer process from CsPbBr3 NC donor to 4CzPN-Ph acceptor under light irradiation, leading to the increased electron density within 4CzPN-Ph molecule and thus the enhanced passivation ability. Together with the formation of compositional gradient layer owing to the halide exchange reaction with CsPbBr3 NCs, the stable perovskite film with reduced defect is obtained, consequently promoting the efficiency up to 11.60 % for CsPbIBr2 and 14.44 % for CsPbI2Br carbon-based devices, with excellent durability under harsh conditions.

Sulfhydryl-modulated CsPbBr3 nanocrystals as a fluorescent tongue for discrimination of formaldehyde releasers and parabens

Adding preservatives to cosmetics have raised many concerns about health issues. Here, we propose a fluorescence sensor array for preservative discrimination based on two types of CsPbBr3 nanocrystals (NCs) modified with two different thiol compounds (i.e., 6-mercapto-1-hexanol (6-MCH) and dithiothreitol (DTT)). The redox reaction between the sulphydryl of 6-MCH and DTT and the carbon oxygen double bonds of preservatives will enhance the fluorescence intensity, which is due to the depletion of superficially decorated DTT and 6-MCH at CsPbBr3. By manipulating this mechanism, different preservatives generate unique fluorescence fingerprint responses through the diverse interactions between targets and two CsPbBr3 NCs. Thus, two types of preservatives, including four formaldehyde releasers and three parabens, were well distinguished at low concentration using linear discriminant analysis (LDA) by this sensor array. Remarkably, preservative identification in hand cream further proves the array’s practical applicability in complex environment.

Enhancing Photocatalytic Attributes of Perovskite Nanocrystals in Aqueous Media via Ligand Engineering.

The remarkable catalytic potential of perovskite nanocrystals (NCs) remains underutilized due to their limited stability in polar media, resulting from the vulnerability of their structure to disruption by polar solvents. In this study, we address this challenge by employing the bolaamphiphilic NKE-12 ligand, which features multiple denticities to effectively shield the surface of CsPbBr3 NCs from polar solvent interactions without compromising their light-harvesting properties. Our research, utilizing electrochemical impedance and photocurrent response measurements, highlights efficient charge separation and charge transfer enabled by NKE-12 ligands, which feature multiple ionic groups and peptide bonds, compared to conventional oleylamine/oleic acid ligands on CsPbBr3 NCs. Through the utilization of purely ligand-derived water-dispersed CsPbBr3/NKE-12 NCs, we successfully showcased their photocatalytic activity for acrylamide polymerization. A series of control experiments unveil a radical-based reaction pathway and suggest the synergistic involvement of photogenerated electrons and holes in producing the O2·- and OH· free radicals, respectively. Our findings emphasize the crucial role of ligand engineering in stabilizing perovskites in water and harnessing their exceptional photocatalytic attributes. This study opens new avenues for applying perovskite NCs in various catalytic processes in polar media.