CsPbBr3 QDs Research Articles

One-step precipitation of stable perovskite CsPbBr3 quantum dots in silicate glass by picosecond laser pulses

One-step precipitation of CsPbBr3 QDs in silicate glass was successfully achieved by picosecond laser pulses. Enabled by spatially selective modification, luminescent QDs are well protected by the inorganic glass matrix. The combination of high-power and high-speed scanning system provides a convenient and flexible route for large-scale in situ fabrication of CsPbBr3 QDs. The dependence of photoluminescence (PL) intensity and absorption band was systematically investigated, and the formation mechanism was briefly discussed. Notable stabilities of CsPbBr3 QDs against moisture, high temperature as well as ultraviolet (UV) radiation were verified by water-proof and thermal/UV-dependent PL tests. Prospective use for light-emitting device and anti-counterfeiting were also demonstrated.

Hybrid CsPbBr3 quantum dots decorated two dimensional MoO3 nanosheets photodetectors with enhanced performance

Molybdenum trioxide (MoO3) have gained considerable attention for their wide applications ranging from optoelectronics, solar cells to energy storage. Herein, we obtained high crystalline MoO3 nanosheets (NSs) through a vapor phase epitaxy (VPE) method. A photodetector (PDs) based on MoO3 NSs was fabricated on the SiO2/Si substrate and the PDs exhibit a striking photoresponse under ultraviolet (UV) light. Furthermore, by introducing a CsPbBr3 QDs the photocurrent of the MoO3 devices was enhanced by 2 orders of magnitude than the pristine counterpart. The enhanced photocurrent could be ascribed to the interfacial charge transfer from CsPbBr3 QDs to MoO3. The hybrid CsPbBr3 QDs/MoO3 photodetectors exhibit high responsivity with high on/off ratio under UV light illumination. Furthermore, the performance of the hybrid device, extending from UV to visible light, has ensured broad spectral response of the device. This work indicates that CsPbBr3 QDs/MoO3 hybrids can be promising for the construction of broad band photodetectors and other optoelectronic devices.

Effect of Glass Composition on Luminescence and Structure of CsPbBr3 Quantum Dots in an Amorphous Matrix.

Glass matrix embedding is an efficient way to improve the chemical and thermal stability of the halide perovskite QDs. However, CsPbX3 QDs exhibit distinct optical properties in different glass matrixes, including photoluminescence (PL) peak position, PL peak width, and optical band gap. In this work, the temperature-dependent PL spectra, absorption spectra, high-energy X-ray structure factor S(Q), and pair distribution function (PDF) were integrated to analyze the structural evolution of CsPbBr3 QDs in different glass matrixes. The results show that the lattice parameters and atomic spacing of CsPbBr3 QDs are affected by the glass composition in which they are embedded. The most possibility can be attributed to the thermal expansion mismatch between CsPbBr3 QDs and the glass matrix. The results may provide a new way to understand the effect of the glass composition on the optical properties of CsPbBr3 QDs in a glass matrix.

Investigation of photophysical insights into the CsPbBr3-porphyrazine system in solution

In this work, a combination of steady-state and time-resolved fluorescence studies is used to examine molecular level excited-state interactions between CsPbBr3 QDs and porphyrazine in solution. Fluorescence quenching investigations show that the CsPbBr3 emission is quenched while the fluorescence of porphyrazine is enhanced. The association constant for the interaction between CsPbBr3 QDs and porphyrazine is determined to be 1.2 × 104 M−1. Time-resolved fluorescence quenching studies exhibit direct evidence of an energy transfer process. This research emphasizes the importance of optimizing both the donor and acceptor properties when designing energy-transfer light-harvesting assemblies.

Highly stable halide perovskites for photocatalysis via multi-dimensional structure design and in situ phase transition.

Lead halide perovskite CsPbBr3 quantum dots (QDs) possess several desirable features which enable them to be promising candidates for photocatalysis. However, the instability caused by their inherent liquid-like ionic properties hampers their further development. Herein, this work employs the surficial molecular modification strategy and a multi-dimensional structure design to ease the instability issue. The additive 2-phenylethanamine bromide (PEABr) can serve as a ligand to compensate for stripping the amine ligands and passivate the surficial bromide vacancy defects of CsPbBr3 QDs in photocatalysis. In addition, PEABr acts as a reactant to form 2D and quasi-2D perovskite nanosheets. The addition of a small amount of these nanosheets into QDs can enhance their general stability due to their unique layered structures. Moreover, PEABr can trigger the phase transition of cubic CsPbBr3 into tetragonal CsPb2Br5. The newly formed Z-scheme homologous heterojunctions further improve the catalytic performance. Simulated photocatalytic dynamics reveals that our multi-dimensional structure favors decreasing the reaction barrier energy and then facilitating the photocatalytic reaction. Therefore, the electron consumption rate of our multi-dimensional perovskites doubles that of pristine CsPbBr3 QDs and also has superior long-term stability.

Modulating the local structure of glass to promote in situ precipitation of perovskite CsPbBr3 quantum dots by introducing a network modifier

High-quality CsPbBr3 QDs were regulated to be precipitated in borosilicate glass by introducing a network modifier, CaF2, and the roles of Ca ions and F ions on the nucleation/growth of CsPbBr3 QDs in glass were revealed.

Steady and transient optical properties of CsPbBr3/Pb3(PO4)2 perovskite quantum dots for white light-emitting diodes

Compared with CsPbBr3 QDs, CsPbBr3/Pb3(PO4)2 QDs with a high PLQY of 75.7% show enhanced excitonic optical properties and improved stability. A high-quality WLED device was realized by integrating the green and red CsPbX3/Pb3(PO4)2 QDs.

Sodium doping for enhanced performance by highly efficient CsPbBr3 quantum dot-based electroluminescent light-emitting diodes

A facile and convenient room-temperature method for synthesizing Na+-ion-doped CsPbBr3 QDs was developed. The photoluminescence performance is improved and high-performance QLED devices are prepared.

Surface ligand engineering involving fluorophenethyl ammonium for stable and strong emission CsPbBr3 quantum dots and high-performance QLEDs

Fluorophenethyl ammonium bromide is introduced in the synthesis of CsPbBr3 QDs and the influence of the fluorination position (ortho, meta, and para) at the benzene ring on the optical properties and stability of CsPbBr3 is systematically evaluated.

Photothermal sensor based on water-soluble CsPbBr3@sulfobutylether-β-cyclodextrins nanocomposite using a thermometer as readout

All-inorganic perovskite quantum dots (CsPbX3 QDs) with bright photoluminescence are suitable for application in optoelectronic field, but their extreme instability and insolubility in aqueous solution limit their development in other fields. Herein, for the first time, we encapsulated CsPbBr3 QDs using sulfobutylether-β-cyclodextrins to form nanocomposite (CsPbBr3@SBE-β-CD nanocomposite) with high water solubility and stability via a host-guest interaction strategy, in which the PL intensity remained above 100% of the initial value after 3 h storage in water. Hydrogen sulfide (H2S) is known to be an important mediator of diverse cellular functions in health and in disease, which is important to develop a selective and portable detection method for H2S. The obtained CsPbBr3@SBE-β-CD nanocomposite was employed to develop a photothermal sensor for quantitative detection of H2S using a thermometer as signal readout. Specifically, the obtained CsPbBr3@SBE-β-CD nanocomposite was used as the photothermal probe while H2S acted as a switch of the photothermal probe, and the photothermal sensor was triggered by the reaction between H2S and CsPbBr3@SBE-β-CD nanocomposite. Notably, the naked eye and fluorescence spectrophotometer could also be the signal readout for this strategy, and their detection range and limit of detection were not better than those of the proposed photothermal sensor. On the basis of this H2S-triggered photothermal sensor, H2S was successfully detected at a concentration as low as 5.0 µM in organs of adult zebrafish at room temperature for 10 min. Such innovative strategy enables new opportunity for the development of affordable assays, especially as point-of-care testing in low-resource settings.

Perovskite Quantum Dots with Ultrahigh Solid-State Photoluminescence Quantum Efficiency, Superior Stability, and Uncompromised Electrical Conductivity.

All-inorganic perovskite quantum dots (PQDs), potentially applicable to high-performance display technologies, are facing challenges when the superior luminescence properties with high stability and uncompromised electrical conductivity are combined. Here, by introducing hexylamine sulfate and reducing the reaction rate, we managed to optimize the surface sacrificial coating of CsPbBr3 QDs. As a result, the colloidal PQDs show a photoluminescence quantum efficiency (PLQE) of 95.8% in solution, and an internal PLQE as high as 97.8% in solid-state films. As far as stability is concerned, the PQDs not only show excellent resistance to polar solvent but also can retain over 84% of the initial PL intensity after continuous heating at 100 °C for 60 min. More importantly, the superior stability is achieved without compromising electrical conductivity. The light-emitting diodes made from these PQDs show a current efficiency of 8.9 cd A-1 with excellent thermal stability.

Phase evolution from CsPbBr3:Cu to Cs4PbBr6:Cu quantum dots with stable blue emission

The toxicity and stability are the main obstacles to the industrial production of Pb-based perovskite quantum dots. Here, Low-toxic Cu-doped Cs–Pb–Br-based perovskite QDs were acquired by room temperature crystallization method. There was a phase evolution of the perovskite QDs from CsPbBr3 to Cs4PbBr6 when the CuBr substance exceeds 30 at.%. In this process, the Cu-doped CsPbBr3 QDs display two emission peaks, containing the main emission peak ∼512 nm and the blue emission ∼435 nm, and the Cu-doped Cs4PbBr6 QDs displays a blue emission at ∼435 nm. The stability experiments of typical samples dispersed in deionized water and ethanol verified that the stability of cu-doped perovskite quantum dots was significantly improved compared with CsPbBr3 and Cs4PbBr6 QDs. The quantum dots with blue emission and excellent stability are expected to become a development direction of low-toxic perovskite.

Efficient Photocatalytic CO2 Reduction by the Construction of Ti3C2/CsPbBr3 QD Composites

Photoreduction of CO2 into useable hydrocarbon fuels has been widely used in the energy conversion field. However, the high carrier recombination rate and the low conversion efficiency of as-prepared catalysts greatly restrict their photocatalytic application. Herein, we synthesize Ti3C2/CsPbBr3 quantum dot (Ti3C2/CsPbBr3 QD) composites by the method of self-assembly, which are used in the photoreduction of CO2. As a result, Ti3C2/CsPbBr3 QD composites exhibit excellent photocatalytic activity and stability for the photocatalytic CO2 reduction. Especially, the generation rate of CO (17.98 μmol h–1 g–1) for Ti3C2/CsPbBr3 QD composites is 9.37 times higher than that of CsPbBr3 QDs (1.92 μmol h–1 g–1), and 97.35% of the activity is still retained after three consecutive cycles. The improved photocatalytic performance is mainly attributed to the construction of the type II-2 heterojunction as the built internal electric field (IEF) in the p–n junction could accelerate the separation for both photoinduced holes and electrons. Therefore, this work provides an insight into the construction of heterojunction photocatalysts with halide perovskite QD materials for photocatalytic applications.

Thermal Stability of CsPbBr3 Perovskite Quantum Dots Assembled with SBA-15

Nowadays, the excellent performance of metal halide perovskite quantum dots (PQDs) has been demonstrated, but the stability is still a perplexing issue. In this paper, the CsPbBr3 QDs were assembled into SBA-15 for the first time. The thermal stability and photoluminescence (PL) intensity of SBA-15@CsPbBr3 QDs were improved. The PL spectra of pure CsPbBr3 QDs have red-shift (~6 nm) with the increasing temperature. However, that of SBA-15@CsPbBr3 QDs have almost no red-shift. The PL intensity of SBA-15@CsPbBr3 QDs decreased slightly after heating and cooling for several times. By comparison, the PL intensity of pure CsPbBr3 QDs decreased more significantly. The experimental results showed that SBA-15 played a significant role in improving the thermal stability of PQDs, which will have an excellent potential for the application of PQDs in the future.

Rapid large-scale synthesis of highly emissive solid-state metal halide perovskite quantum dots across the full visible spectrum

The practical applications of solid-state inorganic CsPbX3 perovskite quantum dots (PQDs) have been restricted by their poor stability. Herein, we report an efficient large-scale synthesis of solid-state CsPbX3 PQDs across the full visible spectra using 3-Aminopropyltrimethoxysilane as ligands at room temperature in open air. The obtained green CsPbBr3 solids display outstanding optical performance with high color purity of 90% and photoluminescence quantum yield of 69.2%. Thanks to the protection of silica coating, the solid-state product shows much higher thermal stability, photo stability and long-term stability than that of naked CsPbBr3 QDs. The blue CsPb(Br/Cl)3 and yellow or red CsPb(Br/I)3 PQDs solids can be simply obtained via using alkali metal halide aqueous solution as additives. The white LED fabricated by combining the obtained green CsPbBr3 QDs solid powders and commercial red K2SiF6: Mn4+ phosphor with a blue LED chip displays high luminous efficiency of 70.47 lm/W and the color gamut can cover over 129.4% of the National Television System Committee standard.

Multidentate ligand approach for conjugation of perovskite quantum dots to biomolecules

Building compatible surface on perovskite quantum dots (PQDs) for applications like sensing analytes in aqueous medium is highly challenging and if achieved by simple means can revolutionize disease diagnostics. The present work reports the surface engineering of CsPbBr3 QDs via “simple ligand exchange process” to achieve water-compatible QDs towards detection of biomolecules. The monodentate oleic acid ligand in CsPbBr3 QDs is exchanged with dicarboxylic acid containing (bidentate) ligands such as folic acid (FA), ethylenediamine tetra-acetic acid (EDTA), succinic acid (SA) and glutamic acid (GA) to develop an efficient water-compatible PQD-ligand system. optical and theoretical studies showed the existence of a stronger binding between the perovskite and succinic acid ligand as compared to oleic acid (OA) and all other ligands. Replacement of OA with SA and retention of crystal structure is validated using spectroscopic and microscopic tools. It is observed that SA ligands facilitate better electronic coupling with PQDs and show significant improvement in fluorescence and stability. Further N-Hydroxy succinimide (NHS), which is a well-known compound to activate carboxyl groups, is used to bind onto SA PQDs as multidentate ligand, to form water stable PQDs. SA PQDs react with NHS (in water) to form multidentate ligand passivated PQDs that show very high photoluminescence (PL) as compared to OA PQDs in toluene. This also results in the formation of an NHS ester that allows bioconjugation with PQDs. This simple probe in water is further utilized for sensing a highly hydrophilic bovine serum albumin (BSA) protein as a model target to demonstrate the potential and effectiveness of this process to create compatible QDs for the successful conjugation of biomolecules. Although the focus of this work is to demonstrate bioconjugation and not achieving higher sensitivity levels, the intrinsic sensing level of these compatible QDs towards BSA shows a detection limit of 51.47 nM, which is above par with other reports in literature.

Rapid detoxification of polluted water using ultrastable TiO2 encapsulated CsPbBr3 QDs in collected sunlight

The CsPbBr3 perovskite quantum dots (CPB PQDs) was prepared using the anti-solvent precipitation method in ambient air. The low water stability of CPB PQDs hinders photocatalytic applications, so colloidal CPB PQDs were encapsulated and protected with TiO2. The thickness of TiO2 encapsulation was controlled by immersing the same volume of CPB PQDs into different concentrations of Titanium (Ti) precursor. The optimum CPB/TiO2 composition degrades 78% Methylene Blue (MB) after 300 min under natural (diffuse) sunlight. Furthermore, the same photocatalyst detoxifies MB more than 99% after 50 min illumination of collected sunlight. This outstanding photocatalysis in collected sunlight is attributed to the improved rate of photoinduced charge carriers and their efficient separation due to favourable band alignment of CPB PQD with TiO2. This work provides a pathway to implement an efficient photocatalyst strategy for environmental remediation in outdoor conditions.

Effect of SiO2 and Al2O3 on the luminescence properties of inorganic perovskite (CsPbBr3) quantum dot glass

In this paper, phosphor silicate glass (PSG) containing CsPbBr3 QDs was prepared by the eutectic method and heat treatment technology. By Using analytical methods including X-ray diffraction, fluorescence testing, and transmission electron microscopy, systematically study the influence of the composition of SiO2 and Al2O3 in the glass matrix on the crystallization and luminescence of QDs, and determine the best raw material composition of CsPbBr3 QD glass (QDG). The results show that the optimal composition ratio of the raw materials is 80NH4H2PO4- 15SiO2- 6SrCO3- 3.4Al2O3- 15Cs2CO3- 7.5PbBr2- 15KBr. The CsPbBr3 QDG made with this raw material composition has the best luminescence performance, which can produce a strong emission peak at 512 nm under the excitation of 390 nm violet light.

Cryogenic‐Temperature Thermodynamically Suppressed and Strongly Confined CsPbBr3 Quantum Dots for Deeply Blue Light‐Emitting Diodes

AbstractSuppressing the naturally ultrafast nucleation and growth rates of perovskite nanocrystals is a big challenge to develop high‐performance deeply blue perovskite light‐emitting diodes. Here, a cryogenic temperature thermodynamically suppressed synthetic strategy using liquid nitrogen is designed to obtain ultrasmall CsPbBr3 quantum dots (QDs; ≈3 nm). Due to its strong confinement effect, the as‐obtained CsPbBr3 QDs present strong deeply blue emission (≈460 nm) with a high quantum yield value of up to 98%, a large exciton binding energy of 301.6 meV, and excellent spectra stability for 60 d under atmosphere environment. This unprecedented regime indicates that cryogenic temperature can eliminate pre‐existing trap states and suppress the nonradiative process. Besides, the resultant perovskite light‐emitting diodes based on ultrasmall CsPbBr3 QDs show deeply blue emission (≈ 460 nm) with a Commission Internationale de l'Eclairage (CIE) color coordinate of (0.145, 0.054), better than the blue National Television Standards Committee (NTSC) standard. Evidently, this cryogenic temperature synthetic strategy will pave the way for the large‐scale synthesis of the strongly confined ultrasmall quantum dots systems and open the door for the development of next generation solid‐state lighting and displays.

Engineering CsPbBr3 quantum dots with efficient luminescence and stability by damage-free encapsulation with a-SiCx:H

Although encapsulation is an effective technique to improve the stability of perovskite quantum dots (PQDs), they are prone to photoluminescence (PL) degradation during encapsulation. Herein, a damage-free plasma-based encapsulation technique in combination with real-time in situ diagnosis is designed for CsPbBr3 QDs films. The CH4/SiH4 plasma has little destructive effects on the CsPbBr3 QDs. The a-SiCx:H films prepared with the CH4/SiH4 plasma by low-temperature plasma-enhanced chemical vapor deposition protect the CsPbBr3 QDs from surface damage during encapsulation, so that the intrinsic PL efficiency is maintained. Furthermore, the PL intensity is improved by increasing the carbon concentration in a-SiCx:H and the CsPbBr3 QDs films encapsulated by a-SiCx:H show long term stability under harsh conditions such as prolonged air exposure, UV light illumination for more than 60 days, immersion in water, as well as thermal treatment at 205 oC.