CsPbX3 Perovskite Quantum Dots Research Articles

Ostwald ripening inhibition by a bipolar ligand achieves long-term-reaction and scalable synthesis of ultra-stable CsPbX3 perovskite quantum dots towards LEDs

All-inorganic perovskite quantum dots (PeQDs) hold immense potential for use in light-emitting diodes (LEDs) due to their excellent optoelectronic properties. However, the scalable synthesis and poor stability have severely hindered their application. Here, we solved both the two issues with “one stone”, namely a bipolar ligand 3-(N,N-dimethyloctadecylammonio) propane sulfonate (ASC18). ASC18 contains a positively charged quaternary ammonium group and a negatively charged sulfonic group, which enables for long-term reaction and gram-level synthesis of PeQDs with outstanding morphology, crystallinity, and optical properties. Density functional theory calculations and experimental studies show that these merits arise from the inhibition of Ostwald ripening by ASC18 due to their simultaneous interaction with undercoordinated Br– and Pb2+ via a bidentate binding mode. Furthermore, ASC18 capped PeQDs present significantly improved stabilities against air, UV irradiation, heat, and polar solvent. Finally, both electroluminescent LEDs and down-conversion white LEDs fabricated with our PeQDs show significant operational stability. This presents a trustworthy avenue to obtain high-quality PeQDs for their practical applications.

Stability of core–shell structure CsPbX3@SiO2 (X = Cl,Br) perovskite quantum dots

In this paper, CsPbX3@SiO2 (X = Cl, Br) with cubic morphology and stable optical properties have been developed. The average thickness of the SiO2 shell is 2 ∼ 6 nm, which has the effect of protecting CsPbX3 and isolating the external environment, passivating the surface and reducing the defect density, thus greatly improving the stability of CsPbX3 PQDs. Based on this, the advantages of APTES as a preparation system CsPbX3@SiO2 is revealed, the mechanism diagram is drawn and the stability improvement mechanism CsPbX3@SiO2 is analyzed in detail, which provides a new idea for the stability improvement of CsPbX3 perovskite quantum dots.

Photoluminescent Bi-doped CsPbX3 (X: Br, I) perovskite quantum dots for optoelectronic devices

Perovskite quantum dots (PQDs) became a hot spot in recent years due to their amazing properties, such as the high photoluminescence quantum yield, tunable emission, and narrow bandwidth being important for their application in different optoelectronic devices. In this work, Bi-doped CsPbBr3 and Bi-doped CsPbI3 PQDs were synthesized through the hot-injection method and compared with pristine CsPbBr3 and CsPbI3 to analyze the effect of Bi and the halogen on their properties. In addition, all the samples were synthesized at 130°C, 150°C, and 170°C with the aim of analyzing the effect of the temperature. The results showed a wide range of the emission wavelength from around 500 nm (Bi-doped CsPbBr3) to 630 nm (Bi-doped CsPbI3) as a consequence of the effect of the halogen in “X” position and a slight blueshift in the main photoluminescence emission band after doping the pristine quantum dots with Bi.Graphical abstractImpact statementWe believe that the work in this article represents an important advance in the application of perovskite quantum dots in optoelectronics applications, such as in LEDs or lasers. We report here the synthesis and characterization of Bi-doped CsPbX3 perovskite quantum dots (PQDs), being X: Br and I. These Bi-doped PQDs show a wide range of the emission wavelength from around 500 nm (Bi-doped CsPbBr3) to 630 nm (Bi-doped CsPbI3) as a consequence of the effect of the halogen in “X” position and a slight blueshift in the main photoluminescence emission band after doping the pristine quantum dots with Bi. Therefore, they are good candidates to fabricate optoelectronic devices such as LEDs and lasers thanks to their high photoluminescence emission and their tunable emission.

Short-chain ligand achieves ultra-stable CsPbX3 perovskite quantum dots for white light-emitting diodes

All-inorganic perovskite quantum dots (PeQDs) have aroused great research interest in white light-emitting diodes (WLED) due to their excellent optoelectronic properties, but the poor stability, caused by dynamically binding long-chain capping ligands, hinders their future practical applications. To address this issue, here, we exploit short-chain butyric acid (BA) to replace long-chain oleic acid (OA) as capping ligand of CsPbX3 PeQDs by a hot-injection method. The addition of BA not only makes the morphology of CsPbBr3 PeQDs uniform and improves the crystallinity but also effectively suppresses nonradiative recombination, achieving a near unit photoluminescence quantum yield of 96%. The BA capped CsPbBr3 PeQDs exhibit high stability up to 180 d stored in ambient environment and also significantly improved resistance against polar solvent, ultra-violet lamp irradiation, and heat, which is rationalized by the strong binding capacity and shortened distance of BA to the PeQDs through ab initio calculations. Furthermore, by combining green-emission CsPbBr3 and red-emission CsPbBr0.8I2.2 PeQDs with blue GaN chip, we achieved WLEDs with excellent luminous properties, showing their great potential in practical application of wide-color-gamut display and lighting.

Advances in the preparation and biological applications of core@shell nanocrystals based on quantum dots and noble metal.

Core/shell structured nanoparticles (NPs) are a novel category of functional materials that have garnered widespread attention due to their advantageous preparation methods, unique characteristics, and multifunctional application prospects, which have shown significant performance in materials chemistry and many other fields, such as electronics, biomedical, pharmaceutical, optics, and catalysis. Although some reviews about core/shell NPs have been published, there is still an intense requirement for an extensive review about the updated literature and new reported core/shell nanomaterials. Colloidal quantum dots (QDs) and noble metal NPs have a very small size, which results in the large surface-to-volume ratio and under-coordinated chemical bonds. As a result, the effort on the design of core-shell structure has been essential for colloidal QDs and noble metal NPs. In this review, the core-shell structures dominated by traditional QDs and CsPbX3 perovskite QDs, as well as noble metal nanocrystals (NCs) were summarized. The applications of the above core-shell structure NCs in medical or biological fields such as sensing, biological imaging, medical diagnostics and therapeutics, immunological diagnosis were discussed. The main objective of this review is to provide a better basis for the synthesis, properties, and biomedical applications of QDs or noble metal core/shell NPs, which is beneficial for the further development of QDs, noble metal NPs, and other NPs.

In situ and General Multidentate Ligand Passivation Achieves Efficient and Ultra-Stable CsPbX3 Perovskite Quantum Dots for White Light-Emitting Diodes.

Inorganic CsPbX3 perovskite quantum dots (PeQDs) show great potential in white light-emitting diodes (WLEDs) due to excellent optoelectronic properties, but their practical application is hampered by low photoluminescence quantum yield (PLQY) and especially poor stability. Herein, we developed an in-situ and general multidentate ligand passivation strategy that allows for CsPbX3 PeQDs not only near-unit PLQY, but significantly improved stability against storage, heat, and polar solvent. The enhanced optical property arises from high effectiveness of the multidentate ligand, diethylenetriaminepentaacetic acid (DTPA) with five carboxyl groups, in passivating uncoordinated Pb2+ defects and suppressing nonradiative recombination. First-principles calculations reveal that the excellent stability is attributed to tridentate binding mode of DTPA that remarkably boosts the adsorption capacity to PeQD core. Finally, combining the green and red PeQDs with blue chip, we demonstrated highly luminous WLEDs with distinctly enhanced operation stability, a wide color gamut of 121.3% of national television system committee, standard white light of (0.33,0.33) in CIE 1931, and tunable color temperatures from warm to cold white light readily by emitters' ratio. This study provides an operando yet general approach to achieve efficient and stable PeQDs for WLEDs and accelerates their progress to commercialization.

Surface Modification Strategy Synthesized CsPbX3 Perovskite Quantum Dots with Excellent Stability and Optical Properties in Water

AbstractThe poor stability of CsPbX3 (X = Cl, Br, I) perovskite quantum dots (PQDs) in polar solvents such as water, seriously hinders their practical application. Herein, 5‐Bromovaleric acid (BVA) is used to replace oleic acid (OA), the most common surface ligand in CsPbX3 PQDs synthesis. Under the synergic action of oleylamine (OLA), CsPbX3 PQDs with high water stability can be synthesized directly in water. Because the carboxyl ligands provided by BVA, and the long chain amines provided by OLA formed hydrophobic shells on the surface of CsPbBr3 PQDs, the obtained CsPbBr3 PQDs still has high luminescence intensity and photoluminescence quantum yield after being dispersed in water for several days, and the luminescence peak is always maintained at 518 nm. In contrast, the luminescence intensity of CsPbBr3 PQDs synthesized with OA and OLA is <1% of the initial intensity after only 30 min. CsPbCl3 and CsPbI3 PQDs synthesized directly in water by this method also show high water stability. In this study, for the first time the synthesis method of CsPbX3 PQDs with high water stability using BVA/OLA as surface ligands is proposed, which provides an effective way to explore the synthesis of PQDs that can maintain stability in water.

Passivation of Surface Defects by X-type Short-Chain Ligands for High Quantum Yield and Stable CsPbX3 Quantum Dots Synthesis and Application in WLEDs

All-inorganic CsPbX3 perovskite quantum dots have excellent optoelectronic properties and are excellent candidates for optoelectronic applications. However, the surface ligands (oleyl ammonium, oleic acid) commonly used in traditional inorganic perovskite quantum dots easily fall off from the quantum dots and their protective power is relatively weak, resulting in poor quantum yield and stability of the quantum dots, limiting their application. In this paper, we introduce an X-type short-chain ligand (DDEAB) passivation strategy to enhance the optoelectronic properties of CsPbX3 quantum dots through a facile room-temperature synthesis method and the strong affinity of X-type ligands for surface atoms. The results of TRPL and X-ray photoelectron spectroscopy showed longer lifetime and stronger surface affinity. This result confirms that didecyldimethylammonium bromide (DDEAB) has better binding to CsPbBr3 QDs and can effectively reduce surface defects and improve quantum yield. As a result, the introduction of short-chain ligands can more effectively passivate the surface halogen defects of CsPbX3 QDs, achieving high quantum yield (>90%) and long-term storage environmental stability. In addition, DDEAB-passivated CsPbBr3 QDs have been successfully applied in white light emitting diodes (WLEDs) with wider color gamut (123%), and good EL stability compared to NTSC TV color standard. Our proposed short-chain ligand DDEAB passivation strategy may provide a reference guideline for the preparation of quantum dots and photovoltaic devices with high photoluminescence and environmental stability.

Multi-color UCNPs/CsPb(Br1-xIx)3 for upconversion luminescence and dual-modal anticounterfeiting.

Advanced hybrid materials have attracted extensive attention in optoelectronics and photonics application due to their unique and excellent properties. Here, the multicolor upconversion luminescence properties of the hybrid materials composed of CsPbX3(X = Br/I) perovskite quantum dots and upconversion nanoparticles (UCNPs, core-shell NaYF4:25%Yb3+,0.5%Tm3+@NaYF4) is reported, achieving the upconversion luminescence with stable and bright of CsPbX3 perovskite quantum dots under 980 nm excitation. Compared with the nonlinear upconversion of multi-photon absorption in perovskite, UCNPs/CsPbX3 achieves lower power density excitationby using theUCNPs as the physical energy transfer level, meeting the demand for multi-color upconversion luminescence in optical applications. Also, the UCNPs/CsPbX3 combined with ultraviolet curable resin (UVCR) shows excellent water and air stability, which can be employed as multicolor fluorescent ink for screen printing security labels. Through the conversion strategy, the message of the security labels can be encrypted and decrypted by using UV light and a 980 nm continuous wave excitation laser as a switch, which greatly improves the difficulty of forgery. These findings provide a general method to stimulate photon upconversion and improve the stability of perovskite nanocrystals, which will be better applied in the field of anti-counterfeiting.

Post-synthetic ammonium hexafluorophosphate treatment enables CsPbBr3 perovskite quantum dots exhibiting robust photoluminescence and environmental stability for white light-emitting diodes

All-inorganic CsPbX3 perovskite quantum dots (QDs) have attracted extensive attention as the promising materials for new-generation optoelectronic applications. However, massive surface defects on CsPbX3 QDs usually result in the inferior photoluminescence (PL) and environmental stability, severely hindering their real applications. For this sake, herein, an effective and low-cost post-synthetic treatment is employed to improve the optical properties and colloidal stability of CsPbBr3 QDs via directly adding the ammonium hexafluorophosphate (NH4PF6) into the as-synthesized CsPbBr3 colloidal QDs. By virtue of the interaction between Pb2+ and PF6−, as well as the similar chemical properties of PF6− and halides, the post-synthetic NH4PF6 treatment is demonstrated to effectively passivate surface defects on CsPbX3 QDs and form the Br-rich organic-inorganic hybrid passivation mode. As a consequence, the NH4PF6-treated CsPbBr3 QDs robust PL emission and long-term stability, which can be successfully applied in white light-emitting diodes (WLEDs), showcasing bright practical application potentials. Our work provides a novel and simple strategy for preparing CsPbBr3 perovskite QDs with excellent PL and environmental stability, which will further promote their commercialization process.

Encoding CsPbX3 perovskite quantum dots with different colors in molecularly imprinted polymers as fluorescent probes for the quantitative detection of Sudan I in food matrices

All-inorganic cesium lead halides (CsPbX3, X = Cl, Br, I) perovskite quantum dots (PQDs) have attracted extensive research attention due to their unique optical properties. However, their instability and sensitivity to air and moisture hinder further use in fluorescent sensing applications. In this work, the construction and application of PQDs encoded molecularly imprinted polymers (MIPs-CsPbX3) for Sudan I detection were proposed. After being encoded the PQDs, the obtained MIPs-CsPbX3 microspheres exhibited high stability for the external environment, remarkable bright fluorescence, and specific recognition for Sudan I. The fluorescent intensity of the MIPs-CsPbX3 microspheres was obviously quenched upon loading Sudan I, and good linear responses in the range of 0.5–150 µg L−1, limit of detection of 0.3 µg L−1, and good recoveries of 95.27 % to 105.96 % in spiked samples were obtained. The developed fluorescent probe provided a selective and sensitive quantified method for Sudan I detection in food matrices.

Efficient purification method for CsPbX3 perovskite quantum dots

CsPbX3 perovskite quantum dots (QDs) have attracted increasing attention for the applications of lighting and display due to their excellent properties. Although the preparation of perovskite QDs has been widely developed, there is still not a universal and efficient method to purify perovskite QDs, which is due to the labile ionic characteristics of the perovskites. Here, a new purification method is proposed by using the addition of a new antisolvent-dimethicone oil (DMO). Compared to the two commonly used purification methods (direct centrifugation and centrifugation with ethyl acetate antisolvent), the sample purified by DMO addition shows the highest photoluminescence quantum yield (PLQY) and stability. Besides, the yield of the samples obtained from DMO addition is also the highest. This new purification method is also suitable for the products prepared by the room temperature method, where large amounts of QDs with high PLQY can be acquired. Furthermore, a simple differential centrifugation method is designed based on this anti-solvent. Size-selected perovskite QDs with narrow size distribution are obtained from this differential centrifugation method.

Facile synthesis of KaCs1−aPbBr3@ molecular sieve SBA-15 composite with improved luminescence and wet/thermal stability

CsPbX3 (XCl, Br, I) perovskite quantum dots (PeQDs) have excellent properties, which makes it the most promising optoelectronic materials for the next generation of light-emitting diodes (LEDs) and display devices fields. However, CsPbX3 PeQDs have poor-term stability and easily decompose in moist or heat conditions. In this paper, the KaCs1−aPbBr3 @SBA-15 composite was prepared at room temperature. Alkali metal ion doping can enhance the luminous intensity and tune the emission spectrum of CsPbBr3 PeQDs, while the introduction of the SBA-15 matrix improves the stability of the KaCs1−aPbBr3 PeQDs (a=0, 0.1, 0.25, 0.35, 0.4, 0.45). When the molar ratio of K+/Cs+ is 0.4 / 0.6, the PL intensity of CsPbBr3 PeQDs increased by 21.4%. The luminous intensity of K0.4Cs0.6PbBr3 @SBA-15 composite is further increased by 18.8% compared to the K0.4Cs0.6PbBr3 PeQDs, and its moisture and heat resistance are significantly improved. The PL intensity of K0.4Cs0 6PbBr3 @SBA-15 can maintain 52% of the initial brightness after immersion in deionized water for 21 days, as well as reaching 95% of the initial value in the heating/cooling cycle treatment. Such excellent properties make the KaCs1−aPbBr3 @SBA-15 composite an ideal material for lighting and display applications.

High-stability CsPbIBr2 nanocrystal with nitrogen-doped graphene quantum dot/titanium dioxide for enhancing rhodamine B photocatalytic degradation under visible light

All-inorganic CsPbX3 perovskite quantum dots have attracted substantial research interest because of their great potential for application on the photoelectronic materials. However, CsPbX3 is sensitive to polar substances and thermal treatment, both of which severely degrade the photoluminescence (PL) properties. In this study, highly stable CsPbIBr2 nanocrystals with nitrogen-doped graphene quantum dots (N-GQD-CsPbIBr2 nanocrystals) were successfully synthesized. The nanocrystals exhibit excellent thermal stability and high chemical stability in a polar environment. Titanium dioxide (TiO2) was combined with N-GQD-CsPbIBr2 nanocrystals to obtain a N-GQD-CsPbIBr2/TiO2 nanocomposite. Photocatalytic activity was assessed by testing the rate of rhodamine B (RhB) degradation under visible-light irradiation. The N-GQD-CsPbIBr2/TiO2 nanocomposite exhibited more efficient RhB degradation after 1 h (90% efficiency) than the N-GQDs, TiO2, the N-GQD-CsPbIBr2 nanocrystals, and the N-GQD/TiO2 nanocomposite. The degradation efficiency of the N-GQDs, TiO2, the N-GQD-CsPbIBr2 nanocrystals after 1 h of approximately 2%, 5%, 3%, and 45% respectively. This enhanced photodegradation was attributed to electron and hole transport in opposite directions at the junction of the N-GQD-CsPbIBr2/TiO2 nanocomposite and reduced recombination of charge carriers, which enable the rapid generation of active species (•OH radicals and •O2− ions).

Inverse opal photonic crystal stabilized CsPbX3 perovskite quantum dots and their application in white LED

Although the perovskite quantum dots (PQDs) have great application prospects, the poor stability of PQDs limits their commercial development. Inspired by the previous works, which employ the hydrophobic polymers and micro-nano structures to encapsulate and protect the PQDs, non-wetting inverse opal photonic crystals (IOPCs) are introduced to improve the stability of the PQDs in this work. In the designed composite, the PQDs are embedded in the porous structures of the IOPCs. The inner large surface area provides enough space for the dispersion of the PQDs, thus preventing the luminescence quenching induced by agglomeration. Meanwhile, the non-wetting of the IOPCs’ outer surface can prevent the PQDs from contacting with water in the natural environment. Under the combined function of the above two protective effects, the luminescence stability of the prepared composite film was improved to more than four months. In addition, since the PQDs are inside the IOPCs, the luminescence properties of the PQDs can be regulated by matching the emission peak of the PQDs with the reflection peak of the IOPCs. A “sandwich” composite film composed of PQDs and IOPCs is also designed, which presents the application potential in white LED.

A facile strategy to synthesize high colour purity blue luminescence aluminium-doped CsPbBr3 perovskite quantum dots

Recently, metal halide perovskite materials (CsPbX3, X = Cl, Br, and I) have attracted extensive attention for designing optoelectronic devices owing to their tuneable bandgap and high photoluminescence quantum yields (PLQYs). However, the corresponding study of CsPbX3 perovskite quantum dots (QDs) with blue luminescence still lags far behind that of their red and green counterparts. Herein, we developed aluminium (Al3+) ion-doped CsPbBr3 perovskite QDs through a supersaturated recrystallization synthetic approach at room temperature. The crystal structure and optical properties of the as-prepared QDs were systematically characterized. The results reveal that the particle size and lattice spacing of Al3+ ion-doped CsPbBr3 QDs decrease as the Al/Pb molar ratio increases, which is attributed to the radius of Al3+ ions being much smaller than Pb2+ ions. A significant blueshift in the luminescence from 503 nm to 465 nm of Al3+ ion-doped QDs is observed as the Al/Pb molar ratio increases. Moreover, high colour purity (wide full-width at half-maximum of 83.3 meV) blue photoluminescence emission at 465 nm with a PLQY of 65.7% is achieved when the Al/Pb ratio reaches 1.0 in the Al3+ ion-doped CsPbBr3 QDs, which shows good stability under ambient atmosphere. These as-prepared high colour purity blue luminescence Al3+ ion-doped CsPbBr3 QDs show promising potential in blue optoelectronic fields.

Improved luminescent performances of CsPbI3 perovskite quantum dots via optimizing the proportion of boron-silicate glass and precipitation processing

In-situ crystallization of CsPbX3 perovskite quantum dots (PQDs) in inorganic glasses has been considered to be a feasible protective method to enhance its stability when exposing in air. However, comparing to CsPbCl3 PQDs and CsPbBr3 PQDs inside glass, CsPbI3 PQDs@glass still suffers from the low photoluminescence quantum yield (PLQY) and extremely poor stability, resulting in keeping away from practical application. Herein, the rigidity of borosilicate glass is optimized through adjusting the molar ratio of B2O3/SiO2 in the glass system, which allows fine-control of precipitation and growth of quantum dots. The highest PLQY value of glass stabilized CsPbI3 reaches 17.1%. Importantly, because of the dense and strong protection of the glass, CsPbI3 PQDs@glass exhibits excellent water resistance and still maintain about 95% luminescence after soaking them in water for 60 days. A series of prototypes light-emitting diode devices were combined by coupling LuAG phosphor, as-made red CsPbI3 PQDs@glass powders with a commercial blue-chip, yielding bright white light luminescence with optimal luminous efficiency of 95 lm/W, color temperature of 5755 K and high color rendering index of 95.

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.

In-situ guanidinium bromide passivation treatment of CsPbBr3 perovskite quantum dots exhibiting high photoluminescence and environmental stability

All-inorganic CsPbX3 perovskite quantum dots (QDs) are of great interest in the new-generation optoelectronic applications. However, the inferior long-term stability of CsPbX3 QDs has severely hindered their real applications. In this paper, we have developed a simple and efficient in-situ guanidinium bromide (GABr) passivation approach to synthesize CsPbBr3 QDs by introducing appropriate amount of GABr into the precursor solution using the traditional hot injection method. The in-situ GABr passivation treatment is demonstrated to effectively improve the crystallinity and regulate the grain size of CsPbBr3 QDs without changing the crystal structure. More importantly, the in-situ GABr passivation treatment strategy can induce the passivation of surface defects and formation of the stable bromine-rich surface with tri-ligand mode. Consequently, the in-situ GABr passivated CsPbBr3 QDs display remarkably improved optical properties and environmental stability. Additionally, the in-situ GABr passivated CsPbBr3 QDs have been successfully employed in photodetectors and white light-emitting diodes (WLEDs), showing great practical application prospects. Our work may afford a new guideline to prepare CsPbBr3 QDs with high photoluminescence and environmental Stability.

CsPbX3 Quantum Dots Embedded in Zeolitic Imidazolate Framework-8 Microparticles for Bright White Light-Emitting Devices

CsPbX3 perovskite quantum dots (QDs) have been receiving extensive attention in the fields of luminescence and photovoltaics. However, the bad stability of the CsPbX3 QDs limited their practical ap...