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Aqueous Carbon Quantum Dot-Embedded PC60-PC <sub/>61</sub> BM Nanospheres for Ecological Fluorescent Printing: Contrasting Fluorescence Resonance Energy-Transfer Signals between Watermelon-like and Random Morphologies
摘要： To go beyond the PC60 surfactant structure, the double-layer micelle morphology in water motivates exploration of altered protocols to produce new morphologies. Furthermore, the low photoluminescence quantum yield of aqueous fullerene-based particles encourages high fluorescence to create a light-emitting display. With this in mind, we established new hybrid n-type nanospheres with carbon quantum dot (CQD)-embedded PC60-PC61BM particles, processed using two different protocols. The homogenizer-assisted PC60-CQD-PC61BM resulted in a watermelon-shaped spherical particle, whereas a circular morphology with randomly embedded CQDs was observed in the microwave-treated hybrids. More surprisingly, the watermelon-shaped colloid induced efficient fluorescence resonance energy transfer (FRET) between the CQD and C60 molecules of PC61BM, and the FRET-mediated emission signature diminished gradually as the stripe patterns collapsed. This phenomenon allowed different fluorescent colors in the colloidal printing film. We thereby provided the new carrier dynamics of the particle photonic activities of the developed aqueous PC60-based colloids with the possibility of ecological utilization.
关键词： water-processable organic semiconductor colloids,fullerene-based nanoparticles,fluorescence resonance energy transfer,ecological fluorescent printing,carbon quantum dots
更新于2025-09-11 14:15:04
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Enhancing acid, base and UV light resistance of halide perovskite CH3NH3PbBr3 quantum dots by encapsulation with ZrO2 sol
摘要： Organic-inorganic methylammonium lead halide CH3NH3PbBr3 (MAPbBr3) perovskite quantum dots (QDs) have great potential in opto-electric devices such as solar cell, laser and light-emitting diode. The greatest challenge for halide perovskite QDs is the poor stability in the environment of air, moisture, acid, base and light illumination. Herein, we introduce a brief, feasible and ef?cient method to improve the stability of MAPbBr3 QDs through encapsulating them in ZrO2 sol framework. This three-dimensional network ZrO2 colloid forms a good coating on the surface of MAPbBr3 QDs. The ZrO2 sol protected MAPbBr3 QDs showed greatly improved acid, base and ultraviolet light illumination resistance. The photoluminescence intensity of MAPbBr3/ZrO2 nanocomposites remained at 95% of the initial value after 4.5 h in base environment and 90% after 10 h in acid environment. The detailed mechanism was discussed.
关键词： Quantum dots,ZrO2,Stability,Halide perovskite
更新于2025-09-11 14:15:04
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Effects of GaN capping layer on carrier occupation and interband transition probability of vertically coupled InGaN/GaN quantum dots
摘要： The carrier occupation and the interband transition probability of wurtzite (WZ) coupled InGaN/GaN quantum dots (QDs) were investigated as a function of the distance d between QDs in a range of 30?70?A. The light emission intensity rapidly decreases with increasing the distance d and becomes minimum near d=50?A. This can be explained by the fact that the matrix element values are significantly reduced with increasing d owing to an increase in the internal field and the quasi-Fermi-level separation shows a minimum value at d=50?A. However, the light intensity slightly begins to increase when d exceeds 50?A because the quasi-Fermi-level separation increases with increasing d. These results can be used as the design guideline of the active region in QD-based optoelectronic devices with a high efficiency.
关键词： optoelectronic devices,interband transition probability,GaN capping layer,InGaN/GaN quantum dots,carrier occupation
更新于2025-09-11 14:15:04
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Two-state lasing at room temperature in InAs/InP quantum dots
摘要： The two-state lasing conditions at room temperature in InAs/InP quantum dot (QD) lasers under a continuous wave electrical bias current are studied. It is found that excited state (ES) lasing is promoted by moderately decreasing spacer thickness and increasing dot-size dispersion in a QD stack, and the physical origins are due to the increased bottleneck effect and inhomogeneous broadening. Moreover, it is proved theoretically that ground state (GS) lasing with high inhomogeneous broadening may result in high phase and intensity noise at a high bias current. Therefore, an appropriate spacer thickness together with appropriate inhomogeneous broadening is critical to the GS and/or ES lasing, which helps an optimal design of laser geometry.
关键词： two-state lasing,spacer thickness,room temperature,InAs/InP quantum dots,inhomogeneous broadening,dot-size dispersion,intensity noise,continuous wave electrical bias,bottleneck effect,phase noise
更新于2025-09-11 14:15:04
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New strategies for colloidal-quantum-dot-based intermediate-band solar cells
摘要： The intermediate-band solar cell (IBSC) concept promises to increase the efficiency limit in a single-junction solar cell through the absorption of below-bandgap-energy photons. Despite their operating principle having been proposed over 20 years ago, IBSCs have not delivered on this promise yet, and the devices fabricated so far, mainly based on embedded epitaxial quantum dots, have instead operated with lower efficiency than conventional solar cells. A new paradigm, based on the exploitation as the intermediate band of the intragap states naturally occurring in the density functional theory description of colloidal (i.e., chemically synthesized) quantum dots, was suggested recently. Here, we revisit this intriguing concept unveiling its shortcomings and propose two alternative schemes: in the first, the localized electron surface trap states, ubiquitously found in commonly synthesized colloidal quantum dots, are used as intermediate bands in strongly coupled films made of small InAs nanocrystals and, in the second scheme, the intermediate band is provided by the conduction-band-minimum-derived miniband in films of larger InAs nanocrystals. Both schemes yield estimated limiting IBSC efficiencies exceeding Shockley-Queisser’s limit for a single absorber.
关键词： efficiency,InAs nanocrystals,intermediate-band solar cell,colloidal quantum dots,Shockley-Queisser limit
更新于2025-09-11 14:15:04
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An Unexpected Transformation of Organic Solvents into 2D Fluorescent Quantum Dots During Ultrasonication Assisted Liquid Phase Exfoliation
摘要： Ultrasonication within organic solvents is widely used to exfoliate layered materials and produce two-dimensional (2D) nanostructures. Several 2D materials synthesized by such liquid phase exfoliation (LPE) approaches are reported to exhibit photoluminescence. In these approaches, it is presumed that while the 2D nanostructures are derived from the layered parent material undergoing delamination, the organic solvent serves as a dispersing medium. However, in this study, we show that the organic solvent also contributes towards formation of 2D nanostructures that are optically active. We show that that bare organic solvent, when exposed to ultrasonication, transforms into 2D photoluminescent carbon quantum dots (CQDs) that display blue, cyan, green, and yellow emissions depending upon the excitation wavelength. Although this finding is intuitive, it has remained unacknowledged in the design of experiments which require ultrasonication of layered materials in organic solvents. Our results suggest that optical properties of dispersions obtained by LPE embody a contribution not only from the 2D nanostructures derived from the layered material but also from the 2D CQDs that are formed as a natural result of the liquid medium being exposed to ultrasonication. We anticipate that this new physical insight would form an important addition to the guidelines for exfoliation and help in rightly inferring the optical properties of the 2D material dispersions produced by these methods.
关键词： 2D nanostructures,Carbon quantum dots,Organic solvents,Liquid phase exfoliation,Ultrasonication,Photoluminescence
更新于2025-09-11 14:15:04
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Kinking effects and transport properties of coaxial BN-C nanotubes as revealed by <i>in situ</i> transmission electron microscopy and theoretical analysis
摘要： The insights into transport behavior and the effects of bending on heterostructures constructed from boron nitride (BN) and carbon (C) nanotubes are important for their flexible device applications because the two systems have equally excellent mechanical but completely different electrical properties. In this work, coaxial BN–C nanotubes have been fabricated and their intrinsic transport properties, as well as structural and electrical response to bending deformation, are studied inside a high-resolution transmission electron microscope. Ballistic, diffusive, and hopping transports within different tube length ranges have been observed. When bending deformation was applied to the tubes, although severe kinking becomes apparent, their transport properties are not notably affected. Meanwhile, both theoretical and experimental analyses confirm that the kink positions depend on the ratio of tube diameter to its length. Possible formation of quantum dots, directly within the kink areas, was predicted through calculations of electron density redistribution between nanotube walls at bending.
关键词： bending deformation,transport properties,BN-C nanotubes,in situ TEM,quantum dots
更新于2025-09-11 14:15:04
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Effects of Hexagonal Boron Nitride Sheets on the Optothermal Performances of Quantum Dots-Converted White LEDs
摘要： Recently, quantum dots-converted white light-emitting diodes (QDs-WLEDs) are attracting numerous attention due to their high luminous efficiency and excellent color quality. As for color conversion material, the quantum dots (QDs) are commonly embedded into a low-thermal-conductivity polymer matrix. In this case, their generated heat during the photoluminescence process can hardly be dissipated into the heat sink, leading to a high working temperature and reduced lifetime. Adding particles with high thermal conductivity to the QDs layer can enhance its thermal conductivity, and thus reduce QDs’ working temperature. At the same time, these particles may affect the optical properties of QDs. However, this problem has still not been deeply studied. In this article, we systematically investigated the effects of the highly thermal-conductive hexagonal boron nitride sheets (hBNSs) on the optothermal performances of QDs/phosphor film in white light-emitting diodes (WLEDs). The thermal conductivity of QDs/phosphor film was significantly increased by 24% after adding 5wt% of 45-μm-diameter hBNS. As for the optical performance, the transparency of the silicone gel film with 45-μm-diameter hBNS was much better than that with 6–9-μm-diameter hBNS under the same weight fraction. Furthermore, the scattering effect of hBNS plays a more important role in enhancing the light conversion performance of QDs than that of phosphor. At last, a color stability test showed the increasing rate of correlated color temperature (IRCCT) of hBNS-added WLEDs are 21% smaller than that of common WLEDs after working 153 h, meaning a better QDs stability in hBNS-added WLEDs.
关键词： light conversion,quantum dots (QDs),Hexagonal boron nitride sheets (hBNSs),thermal conductivity
更新于2025-09-11 14:15:04
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CTAB decorated SnO <sub/>2</sub> nanosheet assembled micro-flowers for photocatalysts
摘要： Self-driven photodetectors are widely used in communication and imaging. As a newly developed semiconductor material, perovskite quantum dots (QDs) are not only bandgap tunable, but also easily combined with other materials. In this paper, a vertical structure self-driven photodetector based on heterojunction of CsPbBr3 QDs and PbS QDs is proposed, and the device is prepared by solution spin coating method. The device can work in visible and near infrared (400–1130 nm) regions, and has excellent performance, such as ultrafast response speed (rise and decay time are 0.4 μs/0.73 μs under 532 nm laser irradiation in self-driven mode, the estimated response time under 1064 nm laser irradiation is about 11.5 μs), more than 100 dB linear dynamic range for both visible and infrared regions, and good stability. Similarly, the responsivity of the photodetector can also reach an average of 10 mA W?1, and the detectivity is 1.13 × 1010 Jones at 0 V bias for 1064 nm laser irradiation. The device combines two kinds of QDs revealing its good prospects and great advantages in self-driven photodetectors and high-speed optical communication devices.
关键词： perovskite,quantum dots,self-driven,heterojunction
更新于2025-09-11 14:15:04
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - High-Color-Purity Microfluidic Quantum Dots Light-Emitting Diodes Using the Electroluminescence of the Liquid Organic Semiconductor Backlight
摘要： We proposed microfluidic quantum dots light-emitting diodes using a liquid organic semiconductor (LOS) and quantum dots (QDs) solutions. LOS and QDs solutions were used as a backlight and a luminophore, respectively. Channels for the QDs solutions were stacked on the LOS backlight. With applying voltage, red photoluminescence (PL) emissions of the QDs solution excited by the LOS backlight, was observed. The full width at half maximum of the red-PL emission was 29.8 nm, which is narrower than that of the LOS backlight by 40%. The proposed device is expected to provide highly-bright flexible displays with high-color-purity.
关键词： liquid organic semiconductor (LOS),Liquid organic light-emitting diodes (OLEDs),high-color-purity,functional organic liquid,quantum dots light-emitting diodes (QLEDs)
更新于2025-09-11 14:15:04