Pure CsPbBr3 Research Articles

Solvent-Free in Situ Synthesis of a CsPbBr3 Nanocrystal/ZrO2 Hybrid Phosphor with Excellent Thermal Stability for White Light-Emitting Diodes.

All-inorganic cesium lead halide perovskite CsPbX3 (X = Cl, Br, I, or mixed) nanocrystals (NCs) are emerging as promising candidates in light-emitting diodes (LEDs) owing to their excellent luminescent properties. However, CsPbX3 NCs are extremely susceptible to the elevated temperature associated with prolonged LED operation due to their low formation energy and soft ionic crystal structure. Here, CsPbBr3 NCs hybridized with ZrO2 were in situ synthesized by a rapid solvent-free method under an ambient environment for the first time, which was also suitable for large-scale production. The as-prepared CsPbBr3/ZrO2 hybrid phosphor not only presented enhanced photoluminescence (PL) properties but also exhibited improved thermal stability. For example, the PL intensity of the CsPbBr3/ZrO2 hybrid phosphor could retain 70% of the initial value at 130 °C, obviously higher than that of 34% for pure CsPbBr3. The exceptional thermal stability of the CsPbBr3/ZrO2 hybrid phosphor could be attributed to the introduction of ZrO2, which effectively preserved the initial perovskite structure of CsPbBr3 during heat treatment, as confirmed by XRD results. The as-prepared CsPbBr3/ZrO2 hybrid phosphor had great practical applications verified by the construction of white LEDs (WLEDs) with a luminance degradation of only 9% after continuous operation for 24 h at the initial luminance of 2000 cd m-2, which was significantly better than that of 63% for control WLEDs. The proposed thermally stable hybrid phosphor is expected to greatly contribute to the industrialization process of perovskites.

One-Step Fabrication of 0D Cs4PbBr6 Perovskite with Nonlinear Optical Properties for Ultrafast Pulse Generation.

Low-dimensional lead halide perovskites demonstrate remarkable nonlinear optical characteristics attributed to their distinctive physical structures and electronic properties. Nevertheless, the investigation into their nonlinear optical properties remains in its incipient stages. This study addresses this gap by precisely controlling solvent volumes to synthesize both 0D Cs4PbBr6 and Cs4PbBr6/CsPbBr3 perovskites. Remarkably, as saturable absorbers, both pure Cs4PbBr6 and Cs4PbBr6/CsPbBr3 composites exhibit favorable nonlinear optical properties within the C-band, showcasing modulation depths of 9.22% and 16.83%, respectively. Moreover, for the first time, Cs4PbBr6 and Cs4PbBr6/CsPbBr3 composites have been successfully integrated into erbium-doped fiber lasers to realize the mode-locking operations. The utilization of the Cs4PbBr6/CsPbBr3 composites as a saturable absorber that enables the generation of conventional soliton mode-locked laser pulses with a pulse duration of 688 fs, and a repetition frequency of 10.947MHz at a central wavelength of 1557nm. Cs4PbBr6 is instrumental in generating laser pulses at a frequency of 10.899MHz, producing pulse widths of 642 fs at the central wavelength of 1531.2nm and 1.02ps at the central wavelength of 1565.3nm, respectively. The findings of this investigation underscore the potential utility of 0D Cs4PbBr6 and Cs4PbBr6/CsPbBr3 composites as promising materials for optical modulation within fiber laser applications.

0D/2D Schottky heterojunction of CsPbBr3 nanocrystals on MoN nanosheets for enhancing charge transfer and CO2 photoreduction

Solar-driven conversion of CO2 to value-added chemical fuels has been regarded as a promising strategy for solving the climate problem and energy crisis. To realize this goal, it is vital to design photocatalysts with abundant catalytic active sites and excellent charge separation efficiency. Here, perovskite nanocrystals (CsPbBr3) were anchored on two-dimensional molybdenum nitride (MoN) using an in-situ growth method, forming a new and effective 0D/2D CsPbBr3@MoN (CPB@MoN) nanoheterosturcture with close contact interface for CO2 photoreduction. The introduction of MoN, acting as a charge transfer channel, could quickly trap the photoinduced charge from CsPbBr3 and provide abundant catalytic sites for CO2 photocatalytic reactions. For optimized CsPbBr3@MoN composites, the CO yield was 13.86μmol/gh−1 without any sacrificial reagent, which was a 4.5-fold enhancement of the pure CsPbBr3. Further, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed the catalytic mechanism for the CO2 photoreduction process. This work provides a new platform for constructing superior perovskite/MoN-based photocatalysts for photocatalytic CO2 reduction.

Photostability of CsPbBr3 nanocrystals modified with poly(ethylene adipate)

All inorganic CsPbBr3 nanocrystals (NCs) have gained significant attention due to their potential as light-emitting diodes, solar cells and other optoelectronic devices. However, to a certain extent, the stability issues of CsPbBr3 NCs under water, light, and thermal conditions limit their further applications. In order to improve stability, this article proposes a strategy of modifying CsPbBr3 NCs with poly(ethylene adipate) (PEA). The surface passivation of macromolecular polymer PEA not only increases the distance between NCs which inhibits the aggregation of small NCs, but also provides a dense protective layer to protect NCs from corrosion by water, air and light. Therefore, the performance of PEA-modified CsPbBr3 NCs in terms of optical properties and stability is significantly improved. The photoluminescence intensity of PEA-modified CsPbBr3 NCs remains at about 40% of the initial intensity when heated to 100 °C, while that of pure CsPbBr3 NCs has decreased to less than 10%. The photoluminescence intensity of PEA-modified CsPbBr3 NCs decreased to 83% of the initial intensity after 7 cycles of heating to 100 °C and then cooling to room temperature, while that of pure CsPbBr3 NCs decreased to 13%. Meanwhile, the PL intensity of PEA-modified CsPbBr3 NCs remained at 66% of the initial intensity after 10 h under 365 nm ultraviolet light, and there is no obvious red shift in PL spectra, while the PL intensity of pure CsPbBr3 NCs only maintained 21% of the initial intensity, accompanied by obvious red shift in PL spectra. The results show that the PEA-modified CsPbBr3 NCs have a positive effect on stability.

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.

Understanding the emission behaviour of 0D Cs4PbBr6 perovskite nanocrystals at room temperature

We report 0D Cs4PbBr6 perovskite nanocrystals emitting at room temperature, synthesized by hot injection technique. Effect of injection temperature (TR) on the emission of Cs4PbBr6 nanocrystals (NCs) has been studied. High-quality NCs are synthesized in the 100 °C–180 °C temperature range. Pure phase Cs4PbBr6 nanocrystals are formed at lower temperatures (TR = 100 °C), while at higher temperatures, CsPbBr3 impurity phase appears along with Cs4PbBr6. Cs4PbBr6 nanocrystals emit blue light with broad emission spectra in the 400–500 nm wavelength range, while a green emission from CsPbBr3 impurities at 520 nm wavelength is observed. The emission spectra from Cs4PbBr6 NCs shows multiple radiative centers in the 400–500 nm range, unaffected by the change in excitation wavelength. The emission of pure Cs4PbBr6 is attributed to charge transfer states of Pb2+ ions and surface states incorporated by presence of ligands on NC surface. Further, it is to be emphasized that the Cs4PbBr6 perovskite NCs are highly stable and maintain their emission even after two years of synthesis.

Stability and photocatalytic performance enhancement of sodium-doped CsPbBr3/Cs4PbBr6 nanocomposites for dye wastewater degradation

The extremely poor stability of lead halide perovskites has always been a challenge. In this paper, CsPbBr3 nanocrystals, CsPbBr3/Cs4PbBr6 nanocomposites and Na-CsPbBr3/Cs4PbBr6 nanocomposites were prepared by thermal injection and ligand-assisted reprecipitation method. The photocatalytic effect and stability of CsPbBr3 in aqueous systems were significantly improved by sodium ions doping and complexation with Cs4PbBr6. The results showed that the photocatalytic degradation rate of 5% Na-CsPbBr3 for Sudan red (III) was 57.8% within 180 min, while that of pure CsPbBr3 was only 14.47%. In the CsPbBr3/Cs4PbBr6 nanocomposites, Na-CsPbBr3/Cs4PbBr6 nanocomposites photocatalyzed nearly 94% of Sudan red (III) in 120 min, while CsPbBr3/Cs4PbBr6 photocatalyzed only 56% of organic dyes in the same time. Cs4PbBr6 can passivate CsPbBr3 in situ to enhance the stability of the perovskite material. In the four cyclic degradation experimental tests in aqueous systems, the nanocomposites maintained good stability performance. This study provides a new way to improve the catalytic performance and stability of perovskite materials.

Stabilization of CsPbBr3 Nanowires Through SU-8 Encapsulation for the Fabrication of Bilayer Microswimmers with Magnetic and Fluorescence Properties.

All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals have drawn great interest because of their excellent photophysical properties and potential applications. However, their poor stability in water greatly limited their use in applications that require stable structures. In this work, a facile approach to stabilize CsPbBr3 nanowires is developed by using SU-8 as a protection medium; thereby creating stable CsPbBr3/SU-8 microstructures. Through photolithography and layer-by-layer deposition, CsPbBr3/SU-8 is used to fabricate bilayer achiral microswimmers (BAMs), which consist of a top CsPbBr3/SU-8 layer and a bottom Fe3O4 magnetic layer. Compared to pure CsPbBr3 nanowires, the CsPbBr3/SU-8 shows long-term structural and fluorescence stability in water against ultrasonication treatment. Due to the magnetic layer, the motion of the microswimmers can be controlled precisely under a rotating magnetic field, allowing them to swim at low Reynolds number and tumble or roll on surfaces. Furthermore, CsPbBr3/SU-8 can be used to fabricate various types of planar microstructures with high throughput, high consistency, and fluorescence properties. This work provides a method for the stabilization of CsPbBr3 and demonstrates the potential to mass fabricate planar microstructures with various shapes, which can be used in different applications such as microrobotics.

Efficient, Color-Stable, Pure-Blue Light-Emitting Diodes Based on Aromatic Ligand-Engineered Perovskite Nanoplatelets.

Perovskite nanoplatelets (NPLs) show great potential for high-color-purity light-emitting diodes (LEDs) due to their narrow line width and high exciton binding energy. However, the performance of perovskite NPL LEDs lags far behind perovskite quantum dot-/film-based LEDs, owing to their material instability and poor carrier transport. Here, we achieved efficient and stable pure blue-emitting CsPbBr3 NPLs with outstanding optical and electrical properties by using an aromatic ligand, 4-bromothiophene-2-carboxaldehyde (BTC). The BTC ligands with thiophene groups can guide two-dimensional growth and inhibit out-of-plane ripening of CsPbBr3 NPLs, which, meanwhile, increases their structural stability via strongly interacting with PbBr64- octahedra. Moreover, aromatic structures with delocalized π-bonds facilitate charge transport, diminish band tail states, and suppress Auger processes in CsPbBr3 NPLs. Consequently, the LEDs demonstrate efficient and color-stable blue emissions at 465 nm with a narrow emission line width of 17 nm and a maximum external quantum efficiency (EQE) of 5.4%, representing the state-of-the-art CsPbBr3 NPL LEDs.

High-performance pure blue-emitting CsPbBr3 nanoplatelets via amino acid-mediated strategy

High-performance pure blue-emitting CsPbBr3 nanoplatelets via amino acid-mediated strategy

3D‐cavity‐confined CsPbBr3 quantum dots for visible‐light‐driven photocatalytic C(sp3)–H bond activation

AbstractMetal halide perovskite (MHP) quantum dots (QDs) offer immense potential for several areas of photonics research due to their easy and low‐cost fabrication and excellent optoelectronic properties. However, practical applications of MHP QDs are limited by their poor stability and, in particular, their tendency to aggregate. Here, we develop a two‐step double‐solvent strategy to grow and confine CsPbBr3 QDs within the three‐dimensional (3D) cavities of a mesoporous SBA‐16 silica scaffold (CsPbBr3@SBA‐16). Strong confinement and separation of the MHP QDs lead to a relatively uniform size distribution, narrow luminescence, and good ambient stability over 2 months. In addition, the CsPbBr3@SBA‐16 presents a high activity and stability for visible‐light‐driven photocatalytic toluene C(sp3)–H bond activation to produce benzaldehyde with ∼730 µmol g−1 h−1 yield rate and near‐unity selectivity. Similarly, the structural stability of CsPbBr3@SBA‐16 QDs is superior to that of both pure CsPbBr3 QDs and those confined in MCM‐41 with 1D channels.

Mn derived growth of CsPbBr3 nanoplatelets for stable and bright orange emission

Abstract Mn-doped perovskites have been extensively studied in optics, magnetism, and electronics due to their orange emission. However, successful Mn doping required a high Mn/Pb feed ratio. In this paper, Mn-doped CsPbBr3 nanoplatelets (NPLs) with bright orange emission were prepared by a two-step slow thermal injection synthesis. The slow injection of precursors effectively slow-down the crystal growth kinetic process and controls the growth of undoped CsPbBr3 NPLs. This process also significantly improves Mn doping efficiency. Mn doping induced the generation of numerous precursor clusters during the growth of CsPbBr3 NPLs, and the formation of these clusters was crucial for enhancing the doping efficiency. The maximum amount of Mn precursor in CsPb0.83Mn0.17Br3 was 50% of Pb precursors. The photoluminescence quantum yields (PLQYs) of CsPb0.94Mn0.06Br3 NPLs reached up to 80.6%, which was 3.1 times of that of CsPbBr3 NPLs. The PL properties of Mn-doped CsPbBr3 NPLs were significantly enhanced compared with pure CsPbBr3 NPLs. The growth process and luminescence mechanism of Mn-doped CsPbBr3 NPLs were discussed. High PLQYs and efficient Mn doping supplied an ideal approach for the preparation of various CsPbX3 (X = Cl, Br, and I) NCs for commercial applications.

Efficient Homojunction/Heterojunction Photocatalyst via Integrating CsPbBr3 Quantum Dot Homojunction with TiO2 for Degradation of Organic Dyes.

A novel TiO2-CsPbBr3(Q) photocatalyst is proposed and rationally constructed, where CsPbBr3 perovskite quantum dots (QDs) of various sizes inside mesopore TiO2 (M-TiO2) are integrated. These perovskite QDs, generated in situ within M-TiO2, establish a type-II homojunction. Interestingly, a Z-scheme heterojunction is simultaneously formed at the interface between CsPbBr3 and TiO2. Due to the coexistence of the type-II homojunction and the Z-scheme heterojunction, photogenerated electrons are effectively transferred from TiO2 to CsPbBr3, thereby suppressing carrier recombination and thus enhancing the degradation of rhodamine B (RhB). Compared with pure CsPbBr3 and TiO2, TiO2-CsPbBr3(Q) shows significantly enhanced photocatalytic performance for RhB degradation. The degradation efficiency of RhB in the presence of the TiO2-CsPbBr3(Q) attains 97.7% in 5 min under light illumination, representing the highest efficiency observed among photocatalysts based on TiO2. This study will facilitate the development of superior semiconductor catalysts for photocatalytic applications.

Preparation of CsPbBr3@Fe2O3 heterojunction nanocrystals for ppb-level H2S sensing

Metal-halide perovskite (MHP) nanocrystals (NCs) have unique advantages in the gas sensing field, but the poor stability restricts their widespread applications. In this work, the CsPbBr3@Fe2O3 heterojunction NCs were synthesized successfully by simple solution process and subsequent surface modification strategy for constructing a gas sensor. The Fe2O3 shell layer was obtained through thermal decomposition of acetylacetone iron (AAI) at 400 °C. The resulting CsPbBr3@Fe2O3 heterostructured NCs exhibit a higher gas-sensing performance to H2S than pure CsPbBr3 and Fe2O3, respectively. Upon exposure to 10 ppm H2S, the response value of 4.12 was obtained at a moderate working temperature of 350 °C, while the response was fast both in terms of response time and recovery time, i.e., 1.84 s and 24.20 s, respectively. This might be the best performance for MHP sensors, to the best of our knowledge. The excellent gas-sensitive response might be attributed to the formation of a heterojunction which promotes the electron migration from CsPbBr3 to Fe2O3.

Synthesis of Size-Adjustable CsPbBr3 Perovskite Quantum Dots for Potential Photoelectric Catalysis Applications.

As a direct band gap semiconductor, perovskite has the advantages of high carrier mobility, long charge diffusion distance, high defect tolerance and low-cost solution preparation technology. Compared with traditional metal halide perovskites, which regulate energy band and luminescence by changing halogen, perovskite quantum dots (QDs) have a surface effect and quantum confinement effect. Based on the LaMer nucleation growth theory, we have synthesized CsPbBr3 QDs with high dimensional homogeneity by creating an environment rich in Br- ions based on the general thermal injection method. Moreover, the size of the quantum dots can be adjusted by simply changing the reaction temperature and the concentration of Br- ions in the system, and the blue emission of strongly confined pure CsPbBr3 perovskite is realized. Finally, optical and electrochemical tests suggested that the synthesized quantum dots have the potential to be used in the field of photocatalysis.

Crystal Growth and Structural and Optical Characterizations of Mixed-Cation MA1-xCsxPbBr3 Halide Perovskite Solid Solutions

Photovoltaic devices fabricated using mixed-cation halide perovskites have demonstrated a superior combination of high efficiency and long operating life. In this study, we synthesize a series of mixed-cation halide perovskites with the composition of MA1-xCsxPbBr3 (MA= CH3NH3), where x varies from 0 to 1. We carefully examine various polar solvents and develop a relatively facile, room temperature solution-based growth method for growing these single crystals under optimal conditions. We conduct a comprehensive investigation of the influence of the Cs+ cation on the structure and optical properties of the perovskite solid solutions. The structural characterization using X-ray diffraction confirms the successful substitution of cesium for the methylammonium (MA) cation in the MA1-xCsxPbBr3 perovskite structure, with a continuous solubility. As the Cs+ content increases, the crystal structure undergoes a gradual transformation from a cubic phase (for MAPbBr3) to an orthorhombic phase (for CsPbBr3). To study the impact of Cs substitution on their optical properties, we perform UV-Vis absorption analysis, and find no significant change in the bandgap value, which remains approximately 2.12 - 2.14 eV for the compositions with x up to 0.7, and for x > 0.7, however, the bandgap value gradually increases to reach 2.21 eV for pure CsPbBr3. This work demonstrates a valid technique for the growth of halide perovskite solid solution crystals, which can be a versatile tool for tailoring the structure, long-term stability, and optoelectronic properties for advanced photovoltaic applications.

Ag@SnO2/CsPbBr3 nanocomposite gas sensor for well-behaved low-concentration ethanolamine sensing at room temperature

It is a novel-effective process for realizing high-efficiency sensing and continuous gas monitoring by introducing precious metals into metal–oxide–semiconductors (MOSs). In this study, Ag is exploited to prepare surface functionalized SnO2 nanoparticles (NPs) and innovative xAg@SnO2/CsPbBr3, activating and catalyzing the gas sensing reactions on semiconductors. The results show that the precious metal Ag NPs promote the directional transport of carriers, thus improving the gas sensing performances. In addition, innovative xAg@SnO2/CsPbBr3 composites originated from Ag@SnO2 NPs and 3-mercaptopropionic acid treated all-inorganic perovskite CsPbBr3 are constructed to further accelerate electron transfer on heterointerfaces, enabling continuous and efficient monitoring of ethanolamine (EA) at room temperature. The sensing properties of Ag@SnO2/CsPbBr3 on various volatile organic compounds are investigated. Compared with pure CsPbBr3, the EA response of as-prepared 2Ag@SnO2/CsPbBr3 is obviously improved by about sevenfold. The response/recovery time is greatly shortened, besides the good stability. Another interesting result for xAg@SnO2/CsPbBr3 is the lower limit of detection of 44.43 ppb. The work demonstrates that Ag modification facilitates the adsorption/desorption rate and the response. Furthermore, the catalytic activation of noble metal Ag NPs and the synergistic interaction of SnO2/CsPbBr3 nano-heterojunctions promote EA sensing performances at room temperature.

Enhanced room-temperature magnetic field effect on spin-polarized excitons of cesium lead bromine-magnetite nanocomposites

The generation and manipulation of spin-polarized electrons are the basis of spintronic applications. Spin injection from a ferromagnetic surface or heterojunction to a semiconductor adjacent layer is often used to create spin-polarized carriers; however, for halide perovskites, due to the mismatch of lattice parameters with most ferromagnets at room temperature, this spin injection is challenging. In this study, we synthesize all-inorganic perovskite CsPbBr3 surrounded by Fe3O4 magnetic nanoparticles. It is found that this nanocomposite shows both magnetization and magnetic field-induced circularly polarized photoluminescence at room temperature. Specifically, with the attachment of Fe3O4 nanoparticles closely on the surface of CsPbBr3 nanocrystals, both the degree of circular polarization and g-factor enhanced by 3.5 times compared with that of pure CsPbBr3. The phenomenon should be due to the formation of exciton magnetic polaron through the coupling of the magnetic aligned nanoparticles with the excitonic state of the host semiconductor in the external magnetic field. The effective spin injection provides a method of controlling the excitonic spin polarization of all-inorganic halide perovskites for spintronic applications.

Enhanced Performance of All‐Inorganic Lead Halide Perovskite/MoS2 Heterojunction Photodetectors by Achieving Interfacial Carrier Separation

A heterojunction interface engineering aimed at improving the performance of all‐inorganic lead halide perovskite photodetectors (PDs) is demonstrated by coupling the two‐dimensional (2D) MoS2 materials with CsPbBr3 used in the chemical vapor deposition method in situ‐grown. The MoS2 carrier extraction layer facilitates electron injection, while the large injection barrier of the CsPbBr3/MoS2 heterojunction depletion layer keeps holes in the perovskite layer, resulting in effective separation of photogenerated carriers at the heterojunction interface. Moreover, the photoluminescence quenching and lifetime shortening of the heterojunction further prove that there is a large amount of charge transfer between the CsPbBr3 and MoS2 interface. As a result, PDs based on the CsPbBr3/MoS2/interdigitated array electrodes (IDA) heterojunction exhibit remarkable performance, such as high photoresponsivity (23.4 A W−1), detectivity (1.48 × 1013 Jones), and switching ratio (1.35 × 105), all of which are an order of magnitude better than pure CsPbBr3 PDs. The heterojunction PD also presents a superior response time (0.07 ms).

Obtaining Ligand-Free Aqueous Au-Nanoparticles Using Reversible CsPbBr3 ↔ Au@CsPbBr3 Nanocrystal Transformation.

Water-hexane interfacial preparation of photostable Au@CsPbBr3 (Au@CPB) hybrid nanocrystals (NCs) from pure CsPbBr3 (CPB) NCs is reported, with the coexistence of exciton and localized surface plasmon resonance with equal dominance. This enables strong exciton-plasmon coupling in these plasmonic perovskite NCs where not only the photoluminescence is quenched intrinsically due to ultrafast charge separation, but also the light absorption property increases significantly, covering the entire visible region. Using a controlled interfacial strategy, a reversible chemical transformation between CPB and Au@CPB NCs is shown, with the simultaneous eruption of larger-size ligand-free aqueous Au nanoparticles (NPs). An adsorption-desorption mechanism is proposed for the reversible transformation, while the overgrowth reaction of the Au NPs passes through the Au aggregation intermediate. This study further shows that the plasmonic Au@CPB hybrid NCs as well as ligand-free Au NPs exhibit clear surface enhanced Raman scattering (SERS) effect of a commercially available probe molecule. Overall, the beautiful interfacial chemistry delivers two independent plasmonic materials, i.e., Au@CPB NCs and ligand-free aqueous Au NPs, which may find important implications in photocatalytic and biomedical applications.