CH3NH3PbBr3 Perovskite Quantum Dots Research Articles

Enhancement of luminous properties and stability of CH3NH3PbBr3 perovskite quantum dots using a low-cost, environmentally friendly and multisite passivation strategy

CH3NH3PbBr3 perovskite quantum dots (PeQDs) have demonstrated excellent performance and are promising for optoelectronic applications. However, poor stability caused by surface defects severely limits their further development. In this work, cheap, green Tartaric acid (Ta) was introduced as a multisite passivator for the synthesis of CH3NH3PbBr3 PeQDs by ligand-assisted reprecipitation at room temperature, and the effect of Ta on the luminous properties and stability of CH3NH3PbBr3 PeQDs was investigated. The hydroxyl group of Ta can anchor Br− of PbBr64− octahedra, reducing the Br vacancy by reducing surface Br− loss, and the carboxyl group can form a coordination bond with Pb2+, all contributing to reducing surface defects, inhibit heavy metal leakage, reduce toxicity and improve luminous properties and stability. The results showed that the FWHM (full width at half maxima) of the Ta-modified PeQDs was 19 nm, PLQY reached 88.24 % and showed bright fluorescence for 100 days at room temperature. Ta-modified PeQDs-based white LED (WLED) emitted cold white light, with ultrahigh luminous efficiency of 121.57 lm/W, color gamut of 127 % of the National Television System Committee (NTSC) standard and high operate stability. Our work provides new ideas for low-cost preparation of perovskite devices with high optoelectronic performance.

Sensitive detection of bilirubin using highly luminescent benzylamine capped CH3NH3PbBr3 perovskite quantum dots

Luminescent organic–inorganic metal halide hybrid perovskite quantum dots (PQDs) as a new class of fluorophores are finding increasing attention towards chemical and biological sensing due to their exceptional photophysical properties. Herein, we synthesized highly fluorescent CH3NH3PbBr3 perovskite quantum dots (B-PQDs) through the ligand assisted reprecipitation method (LARP), using benzylamine as the surface capping ligand. Morphological and opto-structural properties of the as-synthesized B-PQDs were thoroughly investigated using high resolution transmission electron microscopy (HR-TEM), X-Ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), UV–Vis absorption, and fluorescence spectroscopy. The as-synthesized electron-rich amine-capped B-PQDs were employed to study their sensing response towards bilirubin (BL). The aromatic amine capped B-PQDs enhance the sensory response towards BL due to the π-π interaction with BL’s conjugated system. The B-PQDs were found to be highly sensitive towards BL with a stern–volmer constant value ≈ 4.3 × 104 M−1 and limit of detection of 0.42 μM. A panel of characterizations were carried out to investigate the detailed sensing mechanism where resonance energy transfer was found to be the dominant quenching mechanism for BL detection. Our results demonstrated the potential for utilizing organic–inorganic halide perovskite quantum dots for sensing applications, through surface ligand modification tailored for detecting specific analytes.

Stability performance enhancement and mechanistic research of CH3NH3PbBr3 perovskite quantum dots

Organic-inorganic lead halide perovskites quantum dots (OIPeQDs) have shown excellent performance and great promise for commercial applications. However, their instability is a major challenge for their commercial viability. To address this issue, this study optimized the precursor PbBr2 to DMAPbBr3 (DMA+ = (CH3)2NH2+) and synthesis the CH3NH3PbBr3 quantum dots (QDs) by ligand-assisted reprecipitation (LARP) method at room temperature. This process aims to provide a halogen-rich environment to reduce halide vacancy defects, as well as incorporating symmetrical A-site ions, which enhances hydrogen bonding between the halogen and organic cations. The QDs-DMAPbBr3 obtained through this optimized precursor showed preferable time, water and light stability compared to those synthesized through conventional PbBr2. The result demonstrates that the QDs-DMAPbBr3 maintained 85.60% of the initial photoluminescence (PL) value even after one month. To test the stability of the QDs further, the QDs were mixed with deionized (DI) water at a 20:1 ratio, and the QDs-DMAPbBr3 retained 408.33% of the initial PL value after 3 h. In addition, after continuous irradiation under a 365 nm ultraviolet lamp for 20 h, the PL value of the QDs-DMAPbBr3 remained stable, at 65.48% of the initial value. These findings indicate that QDs-DMAPbBr3 possess remarkable stability, which suggests their suitability for a wide range of applications.

Preparation of CH3NH3PbBr3 perovskite quantum dots composites with high photoluminescence quantum yield and good stability

The poor stability always restricts the application of organic halide perovskite quantum dots (PQDs). Herein, hexagonal boron nitride (h-BN) was utilized to stabilize CH3NH3PbBr3 PQDs at low temperature. With the layered structure of h-BN material, CH3NH3PbBr3 PQDs were encapsulated to obtain the h-BN/CH3NH3PbBr3 PQDs nanocomposite powder, which has excellent optical properties and physical stability. The investigated nanocomposites display good green emitting performance with a full width at half maximum (FWHM) of about 27.0 nm, high color purity of 89.0% and high photoluminescence quantum yield (PLQY) of 93.7%. Duo to the excellent thermal conductivity and unique layered structure of the h-BN material, the nanocomposite powder exhibits excellent thermal stability and humidity stability. The assembled white LEDs with green-emitting h-BN/CH3NH3PbBr3 PQDs nanocomposite powder, a commercial red phosphor, and a blue phosphor possess a correlated color temperature (CCT) of 4742 K and 63.1 lm/W luminous efficacy. Besides, the color gamut of the synthetic white light based on green-emitting h-BN/CH3NH3PbBr3 PQDs nanocomposite powder, commercial red phosphor, and blue phosphor is 99.8% of the NTSC standard. In summary, the h-BN/CH3NH3PbBr3 PQDs nanocomposite powder synthesized by the LARP method overcomes the shortcomings of poor stability of PQDs, and has been successfully applied to the preparation of LEDs, expanding the application range of PQDs.

Blinking Mechanisms and Intrinsic Quantum-Confined Stark Effect in Single Methylammonium Lead Bromide Perovskite Quantum Dots.

Lead halide perovskite quantum dots (QDs) are promising materials for next-generation photoelectric devices because of their low preparation costs and excellent optoelectronic properties. In this study, the blinking mechanisms and the intrinsic quantum-confined Stark effect (IQCSE) in single organic-inorganic hybrid CH3 NH3 PbBr3 perovskite QDs using single-dot photoluminescence (PL) spectroscopy is investigated. The PL quantum yield-recombination rates distribution map allows the identification of different PL blinking mechanisms and their respective contributions to the PL emission behavior. A strong correlation between the excitation power and the blinking mechanisms is reported. Most single QDs exhibit band-edge carrier blinking under a low excitation photon fluence. While under a high excitation photon fluence, different proportions of Auger-blinking emerge in their PL intensity trajectories. In particular, significant IQCSEs in the QDs that exhibit more pronounced Auger-blinking are observed. Based on these findings, an Auger-induced IQCSE model to explain the observed IQCSE phenomena is observed.

Modulating Charge Carrier Dynamics and Transfer via Surface Modifications in Organometallic Halide Perovskite Quantum Dots.

We investigate the effect of functionalization by acid/amine combinations of four aromatic capping ligands on the optoelectronic properties of CH3NH3PbBr3 perovskite quantum dots (PQDs). These include benzoic acid (BA), phenylacetic acid (PAA), benzylamine, and isopropyl benzylamine. We observe that charge transfer efficiency in PQD films comprising BA-ligated samples varies between 12% and 95% as the dot density is tuned from 102 to 105 dots/μm2 but is consistently ∼92% over that entire range for PAA-ligated PQDs. As temperature T decreases, initially, recombination is dominated by bound or trapped excitons, but below 80 K, spectral broadening, accompanied by free excitonic behavior, is observed. Our results indicate enhanced charge delocalization at lower values of T, which reduces the level of exciton confinement and recombination decay rates and underlines the importance of investigating PQD-ligand interactions at a fundamental level given the significant effect minute changes in ligand structures have on the optoelectronic properties of quantum dots.

Insights into mechanism of size-controlled synthesis of CH3NH3PbBr3 perovskite quantum dots and large nanoparticles with tunable optical properties

There is a common phenomenon in the preparation of perovskite quantum dots (QDs) by reprecipitation method that large particles were always produced with desired QDs. Understanding the fabrication mechanism can contribute to improve this phenomenon. Herein, we demonstrate a two-step strategy for synthesis of perovskite QDs and large nanoparticles (LNPs), where the growth of QDs and LNPs involves two possible pathways, the quick intercalation reaction process and the dissolution-recrystallization process. Following two pathways, we have created QDs with high photoluminescence quantum yields (ca. 46–71%), tunable size (ca. 3.2–5.4 nm) and LNPs with tunable size from 25 to 300 nm, where their emission wavelength can be tuned from 500 nm to 534 nm. Importantly, based on the comprehensive insight into the formation mechanism, we have achieved the conversion from LNPs to QDs partly through adding surfactants properly, which is expected to pave the way for the development of pure production of perovskite QDs. • We demonstrate a two-step strategy for synthesis of perovskite QDs and large nanoparticles. • The perovskite QDs with tunable size (ca. 2.3–5.4 nm) manifest high photoluminescence quantum yields. • We have achieved the conversion from perovskite large nanoparticles to QDs partly through adding surfactants properly. • The possible mechanism was reported to make clear the function of surfactants on the formation of perovskite QDs and LNPs.

Durable Perovskite UV Sensor Based on Engineered Size-Tunable Polydimethylsiloxane Microparticles Using a Facile Capillary Microfluidic Device from a High-Viscosity Precursor.

In this work, size-tunable polydimethylsiloxane (PDMS) microparticles are fabricated from a high-viscosity oil phase using a facile coflowing capillary microfluidic device and optimized aqueous phase composition. The dispersity of the microparticle size is tuned by engineering of the viscosity of the continuous phase and flow rate ratio that leads us to achieve monodisperse microparticles. Regarding the high potential of the PDMS microparticles for optical applications, efficient environmentally durable perovskite-based UV sensors are fabricated employing the designed size-tunable microparticles. Surprisingly, the UV sensors comprising CH3NH3PbBr3 perovskite quantum dots as UV-sensitive nanocrystals embedded in transparent PDMS microparticles are water resistant because of the high hydrophobicity of PDMS. Remarkably, the UV sensors show a photoluminescence quantum yield as high as 75% that can be employed effortlessly as reusable leak detectors in different fluidic working systems.

Rapid and room temperature synthesis of MAPb1−xSnxBr3−2xCl2x perovskite quantum dots with enhanced lifetime in warm WLEDs: A step towards environmental friendly perovskite light harvester

In this work, a facile approach to develop nontoxic CH3NH3PbBr3 perovskite quantum dots (PQDs) by substituting tin (Sn2+) ion instead of lead (Pb2+) ion and chloride (Cl−) ion instead of bromide (Br−) ion has been reported. Synchronized cation and anion substitution in CH3NH3Pb1−xSnxBr3−2xCl2x PQDs has resulted in commercial-friendly properties like fine-tuning of bandgap, shifting of color emission from green to cyan region (523 nm–490 nm), enhancing structural stability, excitonic lifetime, and color gamut. Presence of Sn2+ cations in +2 state, Cl− anions in −1 state, and ion exchange was confirmed from various spectroscopic and morphological analyses. Photoluminescence quantum yield (PLQY) for unsubstituted CH3NH3PbBr3 was observed as 97.50% and it is reduced to >50% for 15% SnCl2 substituted CH3NH3PbBr3 PQDs because of the presence of defect-related nonradioactive recombination centres while cation and anion changeover. Warm white LED prototype with 123% color gamut encircling as per National Television System Committee Standard was achieved using as prepared CH3NH3Pb1−xSnxBr3−2xCl2x PQDs and commercial red phosphor on the blue LED chip. The inflated colour-gamut, promising PLQY, and slender FWHM of as-synthesized CH3NH3Pb1−xSnxBr3−2xCl2x PQDs illustrate great prospect to explore their utilization in display applications. Reduction in toxicity in perovskite material was confirmed by the biological study.

Spectral behavior of plasmon enhanced fluorescence in organic–inorganic perovskite quantum dot solutions

In this work, the fluorescence emission of hybrid lead bromide perovskite quantum dots is enhanced with the assistance of surface plasmon resonance of gold nanoparticles. Due to the high sensitivity of these quantum dots to an aqueous environment, a water-free synthesis method is chosen for the synthesis of gold nanoparticles. Spherical gold nanoparticles, with a diameter of 13 nm and a surface plasmon resonance peak at 527 nm, are synthesized using oleylamine. CH3NH3PbBr3 perovskite quantum dots, with two different sizes, are also synthesized that show fluorescence emission peaks at 507 and 534 nm. Different concentrations of gold nanoparticles are added to the quantum dots solutions. For quantum dots with a fluorescence peak at a higher energy than localized surface plasmon resonance (LSPR) energy, quenching of fluorescence is observed. However, for quantum dots with a fluorescence peak slightly red-shifted, compared to LSPR, the fluorescence is enhanced by the factor of 2. This fluorescence enhancement is resulted by adding nanoparticles with concentration of 140 μl. By further addition of nanoparticles, quenching of the emission is observed due to the reduction of the distances between the nanoparticles and the perovskite quantum dots.

Enhancing air-stability of CH3NH3PbBr3 perovskite quantum dots by in-situ growth in metal-organic frameworks and their applications in light emitting diodes

Perovskite quantum dots (PQDs) are getting more and more attention for their unique optical properties such as high photoluminescence quantum yield, narrow emission spectrum, and adjustable emission wavelength. However, PQDs, especially, CH3NH3PbX3 PQDs have very poor stability due to their easy decomposition by water and oxygen in the air. Herein, we grew nano-sized CH3NH3PbBr3 PQDs in situ within a kind of micro-sized metal-organic frameworks (Bio-MOF-1) to obtain MOFs-protected PQD composites (PQDs-Bio-MOF-1). The MOF protection only enables the PQD composites to maintain the fluorescence characteristics of PQDs, but also obviously improves the stability of PQDs in the air, showing promising application in light-emitting diodes (LEDs).

Graphene oxide wrapped CH3NH3PbBr3 perovskite quantum dots hybrid for photoelectrochemical CO2 reduction in organic solvents

Lead halide perovskite have primarily considered as photovoltaic materials for luminescent materials and optoelectronic devices. However, lead halide perovskite is assumed to be unsuitable for photoelectrochemical conversion due to the instability in humid environment or polar solvents. Here, we report graphene oxide (GO) wrapped organic-inorganic lead halide perovskite quantum dots (GO/CH3NH3PbBr3 hybrid) for photoelectrochemical conversion CO2 into solar fuels in nonaqueous media. Graphene oxide can protect CH3NH3PbBr3 QDs from erosion by organic solvent, and also serve as electron transport medium to separate photoinduced electrons and holes. Therefore, a photocurrent increase by ca. 200% can be obtained in the GO/CH3NH3PbBr3 hybrid due to improved electron extraction and transport. The GO/CH3NH3PbBr3 electrode exhibits an effective CO2 reduction capacity to CO, yielding 1.05 μmol cm−2 h−1.

Temperature-Dependent Photoluminescence of CH3NH3PbBr3 Perovskite Quantum Dots and Bulk Counterparts.

Organic-inorganic lead halide perovskite is emerging as a potential emissive material for light emitting devices, such as, light emitting diodes (LEDs) and lasers, which has emphasized the necessity of understanding its fundamental opto-physical properties. In this work, the temperature-dependent photoluminescence of CH3NH3PbBr3 perovskite quantum dots (QDs), polycrystalline thin film (TF), and single crystal (SC) has been studied. The optophysical properties, such as exciton-phonon scattering, exciton binding energy, and exciton decay dynamics, were investigated. The exciton-phonon scattering of perovskite is investigated, which is responsible for both PL line width broadening and nonradiative decay of excitons. The exciton binding energy of QDs, TF, and SC were estimated to be 388.2, 124.3, and 40.6 meV, respectively. The observed main exciton decay pathway for QDs is the phonon assisted thermal escape, while that for TF and SC was the thermal dissociation due to low exciton binding energy.

Encapsulation of CH3NH3PbBr3 Perovskite Quantum Dots in MOF-5 Microcrystals as a Stable Platform for Temperature and Aqueous Heavy Metal Ion Detection.

The stability issue of organometallic halide perovskites remains a great challenge for future research as to their applicability in different functional material fields. Herein, a novel and facile two-step synthesis procedure is reported for encapsulation of CH3NH3PbBr3 perovskite quantum dots (QDs) in MOF-5 microcrystals, where PbBr2 and CH3NH3Br precursors are added stepwise to fabricate stable CH3NH3PbBr3@MOF-5 composites. In comparison to CH3NH3PbBr3 QDs, CH3NH3PbBr3@MOF-5 composites exhibited highly improved water resistance and thermal stability, as well as better pH adaptability over a wide range. Luminescent investigations demonstrate that CH3NH3PbBr3@MOF-5 composites not only featured excellent sensing properties with respect to temperature changes from 30 to 230 °C but also exhibited significant selective luminescent response to several different metal ions in aqueous solution. These outstanding characteristics indicate that the stable CH3NH3PbBr3@MOF-5 composites are potentially interesting for application in fluorescence sensors or detectors.

Visual and sensitive fluorescent sensing for ultratrace mercury ions by perovskite quantum dots

Mercury ions sensing is an important issue for human health and environmental safety. A novel fluorescence nanosensor was designed for rapid visual detection of ultratrace mercury ions (Hg2+) by using CH3NH3PbBr3 perovskite quantum dots (QDs) based on the surface ion-exchange mechanism. The synthesized CH3NH3PbBr3 QDs can emitt intense green fluorescence with high quantum yield of 50.28%, and can be applied for Hg2+ sensing with the detection limit of 0.124 nM (24.87 ppt) in the range of 0 nM–100 nM. Furthermore, the interfering metal ions have no any influence on the fluorescence intensity of QDs, showing the perovskite QDs possess the high selectivity and sensitivity for Hg2+ detection. The sensing mechanism of perovskite QDs for Hg2+ is has also been investigated by XPS, EDX studies, showing Pb2+ on the surface of perovskite QDs has been partially replaced by Hg2+. Spot plate test shows that the perovskite QDs can also be used for visual detection of Hg2+. Our research indicated the perovskite QDs are promising candidates for the visual fluorescence detection of environmental micropollutants.

Homogeneous Synthesis and Electroluminescence Device of Highly Luminescent CsPbBr3 Perovskite Nanocrystals

Highly luminescent CsPbBr3 perovskite nanocrystals (PNCs) are homogeneously synthesized by mixing toluene solutions of PbBr2 and cesium oleate at room temperature in open air. We found that PbBr2 can be easily dissolved in nonpolar toluene in the presence of tetraoctylammonium bromide, which allows us to homogeneously prepare CsPbBr3 perovskite quantum dots and prevents the use of harmful polar organic solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. Additionally, this method can be extended to synthesize highly luminescent CH3NH3PbBr3 perovskite quantum dots. An electroluminescence device with a maximal luminance of 110 cd/m2 has been fabricated by using high-quality CsPbBr3 PNCs as the emitting layer.

A facile synthesis of CH3NH3PbBr3 perovskite quantum dots and their application in flexible nonvolatile memory

In this work, we present a simple and facile one step synthesis strategy to prepare CH3NH3PbBr3 perovskite quantum dots and apply them into the nonvolatile memory. Resistive switching phenomenon was observed in this perovskite quantum dots and polymer composite based memory device with the ON/OFF current ratio larger than 103 as well as good reproducibility and reliability. Flexible memory was also demonstrated, and a possible resistance switching mechanism was discussed. Our work paves a way for the application of organolead halide perovskite quantum dots in flexible and transparent nonvolatile memories.

Control of Emission Color of High Quantum Yield CH3NH3PbBr3 Perovskite Quantum Dots by Precipitation Temperature.

Emission color controlled, high quantum yield CH3NH3PbBr3 perovskite quantum dots are obtained by changing the temperature of a bad solvent during synthesis. The products for temperatures between 0 and 60 °C have good spectral purity with narrow emission line widths of 28-36 nm, high absolute emission quantum yields of 74% to 93%, and short radiative lifetimes of 13-27 ns.