All-inorganic Halide Perovskite Quantum Dots Research Articles

Remarkable emission enhancement of CsPbBr3 quantum dots based on an Ag nanoparticle-Ag film plasmonic coupling structure.

All-inorganic halide perovskite quantum dots (QDs) have recently received much attention due to their excellent optoelectronic properties. And their emission properties still need to be improved for further applications. Here, we demonstrated a remarkable emission enhancement of the CsPbBr3 QDs based on an Ag nanoparticle-Ag film plasmonic coupling structure. Through precise control of the gap distance between Ag nanoparticle and Ag film, the localized surface plasmon resonance (LSPR) peak was tuned to match the emission wavelength of the CsPbBr3 QDs. We achieved a 30-fold fluorescence intensity enhancement and a lower lasing threshold, which is 25% of that of the CsPbBr3 QDs without plasmonic coupling structure. It is attributed to that the plasmonic coupling structure exhibits an extremely strong local electric field owing to the coupling between LSPR of Ag nanoparticle and surface plasmon polariton of Ag film. This work provides an effective way to enhance the optical emission of perovskite QDs and promotes the further exploration of on-chip light source.

APTES and CTAB Synergistic Induce a Heterozygous CsPbBr3/Cs4PbBr6 Perovskite Composite and its Application on the Sensitive Fluorescent Detection of Iodide ions.

Recently, all-inorganic halide perovskite quantum dots (IPQD) as a new fluorescent material with excellent fluorescence properties have attracted wide attention. However, their instability in polar solvents is the main factor hindering their application in analysis. Herein, a heterozygous perovskite (CsPbBr3/Cs4PbBr6) was simultaneously prepared and stabilized by a silylanization strategy using (3-aminopropyl)-triethoxysilane (APTES) and cetyltrimethyl ammonium bromide (CTAB) assisted precipitation encapsulation method. The synthesized CsPbBr3/Cs4PbBr6 emitted an independent fluorescence at 520nm. The obtained CsPbBr3/Cs4PbBr6 exhibited good stability in ethanol/water mixtures. It was used as a fluorescent probe for sensitively detecting iodide ions (I-) by fluorescence quenching mechanism in the concentration range of 1 ~ 70.0 µM with the detection limit (LOD) of 0.83 µM (relative standard deviation (RSD) = 1.33%, n = 20). The simplicity and high selectivity of the proposed fluorescent analysis method were the prominent features. This work could be extended to the other target ion detection by a perovskite fluorescent quenching.

"Whole-Body" Fluorination for Highly Efficient and Ultra-Stable All-Inorganic Halide Perovskite Quantum Dots.

Inherent "soft" ionic lattice nature of halide perovskite quantum dots (QDs), triggered by the weak Pb-X (X=Cl, Br, I) bond, is recognized as the primary culprit for their serious instability. A promising way is to construct exceedingly strong ionic interaction inside the QDs and increase their crystal cohesive energy by substituting the interior X- with highly electronegative F- , however, which is challenging and hitherto remains unreported. Here, a "whole-body" fluorination strategy is proposed for strengthening the interior bonding architecture of QDs, wherein the F- are uniformly distributed throughout the whole nanocrystal encompassing both the interior lattice and surface, successfully stabilizing their "soft" crystal lattice and passivating surface defects. This approach effectively mitigates their intrinsic instability issues including light-induced phase segregation. As a result, light-emitting devices based on these QDs exhibit exceptional efficiency and remarkable stability.

Reviving aged CsPbBr3 quantum dots by triallylamine etching

All-inorganic halide perovskite quantum dots are widely known to suffer luminescence degradation owing to their intrinsic instability in atmospheric circumstances. Their high surface energy and weak internal ionic bonding could result in quantum dot agglomeration and structural degradation. In this work, we demonstrate that triallylamine is an efficient recovery agent to reignite the luminescence emission of aged CsPbBr3 quantum dots. The aged CsPbBr3 quantum dots re-emit bright green light instantly after triallylamine etching. The X-ray photoelectron spectroscopy results indicate a noticeable decrease of surface under-coordinated Pb ions content, leading to surface re-healing and photoluminescence quantum yields increasing. The unique emission recovery could reveal the details of CsPbBr3 quantum dot surface variety and facilitate the development of perovskite quantum dot display devices.

Surface ligand modified cesium lead bromide/silica sphere composites for low-threshold upconversion lasing

In recent years, all-inorganic halide perovskite quantum dots (QDs) have drawn attention as promising candidates for photodetectors, light-emitting diodes, and lasing applications. However, the sensitivity and instability of perovskite to moisture and heat seriously restrict their practical application to optoelectronic devices. Recently, a facile ligand-engineering strategy to suppress aggregation by replacing traditional long ligands oleylamine (OAm) during the hot injection process has been reported. Here, we further explore its thermal stability and the evolution of photoluminescence quantum yield (PLQY) under ambient environment. The modified CsPbBr 3 QDs film can maintain 33% of initial PL intensity, but only 17% is retained in the case of unmodified QDs after 10 h continuous heating. Further, the obtained QDs with higher initial PLQY (91.8%) can maintain PLQY to 39.9% after being continuously exposed in air for 100 days, while the PLQY of original QDs is reduced to 5.5%. Furthermore, after adhering CsPbBr 3 QDs on the surface of a micro SiO 2 sphere, we successfully achieve the highly-efficient upconversion random laser. In comparison with the unmodified CsPbBr 3 QDs, the laser from the modified CsPbBr 3 QDs presents a decreased threshold of 79.81 μJ / cm 2 and higher quality factor ( Q ) of 1312. This work may not only provide a facile strategy to synthesize CsPbBr 3 QDs with excellent photochemical properties but also a bright prospect for high-performance random lasers.

Perovskite versus ZnCuInS/ZnS Luminescent Nanoparticles in Wavelength-Shifting Layers for Sensor Applications.

In this work, the application of quantum dots is evaluated in order to sensitize the commercially popular Si detectors in the UV range. The wavelength-shifting properties of two types of all-inorganic halide perovskite quantum dots as well as ZnCuInS/ZnS quantum dots are determined in order to assess their potential in the effective enhancement of the sensors’ detection range. In a further part of the study, the wavelength-shifting layers are formed by embedding the quantum dots in two kinds of polymers: PMMA or Cyclic Olefin Polymer. The performance of the layers is evaluated by transmission and PLE measurement. Incorporating the nanoparticles seemingly increases the transmittance in the UV range by several percent. The observed phenomenon is proportional to the quantum dots to polymer concentration, which indicates the successful conversion action of the luminescent agents.

White Lght Emission from the Tb3+/Eu3+ Co-doped All-inorganic Halide Perovskite Quantum Dots in Ambient Air

White Lght Emission from the Tb3+/Eu3+ Co-doped All-inorganic Halide Perovskite Quantum Dots in Ambient Air

Investigation of random lasing from all-inorganic halide perovskite quantum dots prepared under ambient conditions.

Random lasing from CsPbBr3 quantum dots (QDs) prepared by the hot injection method under ambient conditions has been investigated. The lasing characteristics and performance were related to the thickness and aggregation of the QDs film on a glass substrate. The perovskite emitted linear polarized ASE from the edge of the prepared sample as pump energy above a certain threshold, owing to the gain guiding effect. In comparison to the Q-switched Nd:YAG laser, the prepared perovskite random lasers produced a speckle reduced image with a lower contrast of around 0.051. Through temperature-dependent measurements under a surface normal emission configuration, the photon energy of ASE revealed a red shift as the temperature increased and showed a larger characteristic temperature of around 230 K. This result illustrates that the perovskite prepared under ambient conditions can be a promising material for a microcavity laser in the near future.

Composition-dependent optical limiting behavior of all-inorganic halide perovskite quantum dots

Abstract Nonlinear optical nanostructured materials are gaining interest as optical limiters for various applications. Here, all-inorganic halide perovskite quantum dots (PQDs, SiO2@CsPbX3 (X = Cl, Br, I) QDs) with tunable composition were prepared via ligand assisted reprecipitation, using 3-aminopropyltriethoxysilane as a ligand. The formation of the SiO2@CsPbX3 QDs was confirmed by transmission electron microscopy, X-ray diffraction, infrared spectroscopy, ultraviolet–visible absorption spectroscopy and photoluminescence spectroscopy. The composition-dependent optical limiting (OL) behavior of the SiO2@CsPbX3 QDs was observed using nanosecond and picosecond laser pulses at a wavelength of 532 nm. The SiO2@CsPbBr3 QDs exhibit favorable OL properties. Their OL threshold for the nanosecond laser pulse is 1.68 J/cm2, which is comparable to that of carbon nanotube suspension (a benchmark optical limiter). The presence of chloride or iodide in the SiO2@CsPbX3 QDs leads to weaker OL performance. The OL behavior of the SiO2@CsPbBr3 QDs is attributed to the narrow band gap, large average size, abundant charge carriers under laser excitation and high stability. The OL mechanism was investigated using the open-aperture and closed-aperture techniques. The OL behavior of the SiO2@CsPbX3 QDs is largely attributed to the combined mechanisms of nonlinear absorption and nonlinear refraction. These results reveal the physical processes of the composition-dependent OL properties of the CsPbX3 QDs. These findings provide a means to tailor the OL response of PQDs by controlling the halide ion ratio.

Lead-free all-inorganic halide perovskite quantum dots: review and outlook

Halide perovskite is attracting significant attention in optoelectronic because of its unique properties. Lead-free halide perovskites, in particular, have been studied intensively for their nontoxicity. In addition to the attention given to lead-free halide perovskites, the manufacture of these materials on a quantum scale has also received considerable attention due to the quantum confinement effect. This review discusses the current status of lead-free, all-inorganic halide perovskite quantum dots (LFAIHP QDs). First, synthetic methods for producing quantum dots are introduced; then materials are discussed with a focus on tin, bismuth, antimony, copper-based and double perovskite quantum dots. The properties of these materials-such as their physical structure, optical properties, electrical properties, and stability-are discussed. The application of these materials for solar cells, light-emitting diodes, photodetectors, photocatalysts, and memory devices are also examined. Finally, the limitations of LFAIHP QDs, possible methods to overcome them and prospects for these materials in the future are provided.

Modulating Charge-Carrier Dynamics in Mn-Doped All-Inorganic Halide Perovskite Quantum Dots through the Doping-Induced Deep Trap States.

Transition-metal ion doping has been demonstrated to be effective for tuning the photoluminescence properties of perovskite quantum dots (QDs). However, it would inevitably introduce defects in the lattice. As the Mn concentration increases, the Mn dopant photoluminescence quantum yield (PLQY) first increases and then decreases. Herein the influence of the dopant and the defect states on the photophysics in Mn-doped CsPbCl3 QDs was studied by time-resolved spectroscopies, whereas the energy levels of the possible defect states were analyzed by density functional theory calculations. We reveal the formation of deep interstitials defects (Cli) by Mn2+ doping. The depopulation of initial QD exciton states is a competition between exciton-dopant energy transfer and defect trapping on an early time scale (<100 ps), which determines the final PLQY of the QDs. The present work establishes a robust material optimization guideline for all of the emerging applications where a high PLQY is essential.

Flexible, Printable Soft-X-Ray Detectors Based on All-Inorganic Perovskite Quantum Dots.

Metal halide perovskites represent a family of the most promising materials for fascinating photovoltaic and photodetector applications due to their unique optoelectronic properties and much needed simple and low-cost fabrication process. The high atomic number (Z) of their constituents and significantly higher carrier mobility also make perovskite semiconductors suitable for the detection of ionizing radiation. By taking advantage of that, the direct detection of soft-X-ray-induced photocurrent is demonstrated in both rigid and flexible detectors based on all-inorganic halide perovskite quantum dots (QDs) synthesized via a solution process. Utilizing a synchrotron soft-X-ray beamline, high sensitivities of up to 1450 µC Gyair -1 cm-2 are achieved under an X-ray dose rate of 0.0172 mGyair s-1 with only 0.1 V bias voltage, which is about 70-fold more sensitive than conventional α-Se devices. Furthermore, the perovskite film is printed homogeneously on various substrates by the inexpensive inkjet printing method to demonstrate large-scale fabrication of arrays of multichannel detectors. These results suggest that the perovskite QDs are ideal candidates for the detection of soft X-rays and for large-area flat or flexible panels with tremendous application potential in multidimensional and different architectures imaging technologies.

Photocatalytic and Photoelectrochemical Degradation of Organic Compounds with All-Inorganic Metal Halide Perovskite Quantum Dots.

Inspired by the outstanding optoelectronic properties reported for all-inorganic halide perovskite quantum dots (QDs), we have evaluated the potential of these materials toward the photocatalytic and photoelectrochemical degradation of organic compounds, taking the oxidation of 2-mercaptobenzothiazole (MBT) as a proof-of-concept. First, we determined electrochemically the energy levels of dispersions of perovskite QDs with different band gaps induced by the different ratios between halides (Br and I) and metallic cations (Pb and Sn). Then, we selected CsPbBr3 QDs to demonstrate the photocatalytic and photoelectrochemical oxidation of MBT, confirming that hole injection takes place from CsPbBr3 QDs to MBT, resulting in the total degradation of MBT as evidenced by electrospray mass spectrometry analyses. Although the stability and toxicity of these QDs are major issues to address in the near future, the results obtained in the present study open promising perspectives for the implementation of solar-driven catalytic strategies based on these fascinating materials.

Photoinstable hybrid all-inorganic halide perovskite quantum dots as single downconverters for white light emitting devices

Abstract All-inorganic CsPbX3 (X = I, Br, Cl) perovskite quantum dots (QDs) are emerging as potential candidates for photoelectric devices such as light-emitting diodes (LEDs), solar cells etc. due to their outstanding optical properties including tunable bandgap, narrow size distribution and high photoluminescence (PL) quantum yield (QY). However, instability originated from the strong anion-exchange effect and the lower melting temperature hinders their further practical application. Here, blue emission CsPbBr1.5Cl1.5 QDs with peak wavelength ∼450 nm are prepared by means of hot injection method, and mesoporous silica particles are introduced to wrap them. On one hand, the silica coat, protecting the core QDs from oxygen and humidity somewhat, the stability of the PL QYs and the luminescence of the CsPbBr1.5Cl1.5 QDs, as well as the emission and vision properties of the devices based on these QDs are improved evidently. On the other hand, by integrating the prepared blue emission CsPbBr1.5Cl1.5 QDs or the silica-coated CsPbBr1.5Cl1.5 QDs as single downconverters on violet chips with emission wavelength 365 nm, surprisingly, we observe a new peak ∼550 nm in the PL spectrum of the resultant devices, except for the originate blue emission. We speculate that the new emission peak, which is helpful for the construction of white LEDs (WLEDs), is originated from the bromide-enriched majority domains resulted from the photo-induced segregation of CsPbBr1.5Cl1.5 QDs. The fabricated WLEDs based on CsPbBr1.5Cl1.5@SiO2 QDs, in comparison with that based on CsPbBr1.5Cl1.5 QDs, exhibits stable color rendering index (CRI) with the least variation of 1.4, and stable color correlated temperature (CCT) with the least variation of 325 K. These results suggest that the large full width of half maximum of the new emission benefits for the construction of WLEDs, and mesoporous silica particles serving as coat layer hold great promise for the improvement of performance stability for the devices based on CsPbBr1.5Cl1.5@SiO2 QDs.

Highly stable and water-soluble monodisperse CsPbX3/SiO2 nanocomposites for white-LED and cells imaging

In spite of the excellent optical properties of all-inorganic halide perovskite quantum dots (PQDs), they still suffer from inherent poor stability even when exposed to moisture from the atmosphere, restricting their applications, especially in white-light-emitting diodes (LEDs) and cells imaging. Here, we proposed a strategy by encapsulating the CsPbX3 (X = Cl, Br, I) PQDs into silica nanoplates to prepare highly stable and water-soluble CsPbX3/SiO2 nanocomposites. First, the 120 nm monodisperse CsPbX3/SiO2 nanocomposites inlayed with several CsPbX3 PQDs were fabricated via the modified Stöber method. After coating, their stability exposed in the air was largely improved for all the CsPbX3 (X = Cl, Br, I) PQDs without changing their emission peaks and full-width at half-maximum, attributed to the suppression of the anion-exchange and decomposition. Moreover, further experiments demonstrated that the CsPbX3/SiO2 nanocomposites were highly water-soluble and stable in the water. Their applications in LEDs and cell imaging demonstrated their ultrastability and high biocompatibility. Therefore, this study shows the possibility of their use in photoelectric devices and biological applications.

A simple method to improve the performance of perovskite light-emitting diodes via layer-by-layer spin-coating CsPbBr3 quantum dots.

Recently, all-inorganic halide perovskite quantum dots have become a very promising material for light-emitting diodes. Herein, we demonstrate a facile method, namely, layer-by-layer spin-coating of CsPbBr3 QDs to improve device performance. After optimization of the number of emissive layers, the maximum EQE can be increased from an initial value of 0.69% to 2.31%. Additionally, we inserted a CBP layer between PEDOT:PSS and CsPbBr3 multilayers to balance charge transportation and recombination. As a result, a 37% improvement in EQE (up to 3.16%) and highest luminance of 2629 cd m−2 are obtained.