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Efficient All-Inorganic CsPbBr <sub/>3</sub> Perovskite Solar Cells by Using CdS/CdSe/CdS Quantum Dots as Intermediate Layers
摘要： Highly e?cient all-inorganic perovskite solar cells require a fast charge transfer from CsPbBr3 to TiO2 to reduce the recombination from trap states. Herein, we insert a CdS/CdSe/CdS quantum dot (QD) layer between the TiO2 and CsPbBr3 layers to fabricate all-inorganic perovskite solar cells. By tuning the thicknesses of the CdSe layer of CdS/CdSe/CdS QDs, the conduction band (CB) levels can be adjusted to -3.72~-3.87 eV. After inserting the QD intermediate layer, the energy o?set between the CB of TiO2 and CsPbBr3 is reduced, thus leading to a charge transfer rate boost from 0:040 × 109 to 0:059 × 109 s?1. The power conversion e?ciency (PCE) of the solar cell with QD intermediate layer achieves 8.64%, which is 20% higher than its counterpart without QDs.
关键词： CdS/CdSe/CdS quantum dots,power conversion efficiency,charge transfer,all-inorganic perovskite solar cells
更新于2025-09-23 15:21:01
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Transition metal nanohybrid as efficient and stable counter electrode for heterostructure quantum dot sensitized solar cells: A trial
摘要： Counter electrodes are critical components of third generation solar cells. A simple strategy of utilizing iso-structural analogue of graphene, namely 2D molybdenum di-sulphide as nanohybrid with CuS as counter electrode is explored in this work. Formation of heterostructure photoanode with CdSe/CdS quantum dots along with nano-hybrid counter electrode has significantly boosted current density and open circuit voltage. The designed heterostructure and the counter electrode performs exceptionally well with good stability due to synergistic effect, thus spiking new hopes in achieving high efficiency in quantum dot solar cells.
关键词： Hall effect,CuS-MoS2 nanohybrid,CdSe/CdS heterostructures,Mobility
更新于2025-09-23 15:21:01
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Effect of Polymer Capping on Photonic Multi-Corea??Shell Quantum Dots CdSe/CdS/ZnS: Impact of Sunlight and Antibacterial Activity
摘要： The highly luminescent CdSe/CdS/ZnS core?multi-shell quantum dots (QDs) were prepared without a protective atmosphere through the precursor injection method (phosphine free) in paraffin liquid and oleic acid. Polymers (PEG, PVA, PVP, and PAA) were coated to CdSe/CdS/ZnS core?multi-shell quantum dots to increase stability. However, core?multi-shell structured QDs reveal enhanced emission in the range 355?410 nm by suppressing the defect sensitive cores and nonradioactive recombination in PL spectra. The cubic zinc blended quantum dots with crystallite size in the range 22?44 nm, as confirmed by XRD, were obtained. The resultant absorption spectra of all the samples showed that the samples were absorbent in the UV region over the 302?380 nm range. In the FT-IR spectrum 712, 731, and 400?700 cm?1 band values were assigned to CdSe, CdS, and ZnS band stretching, respectively. Images of CdSe, CdSe/CdS, and CdSe/CdS/ZnS quantum dots obtained from the SEM were spherical whereas QDs capped with different polymers (PEG, PVA, PVP, and PAA) showed nanofibers that were linear and homogeneous size ranged between 12 and 38 nm. These as prepared QDs were placed under visible light for 48 h. After absorbing UV light, the range of UV?vis intensity was enhanced until 389?464 nm and emission intensity enhanced until 492?509 nm, which was confirmed by UV and PL spectra. CdSe/CdS/ZnS QDs with organic ligands revealed antibacterial activity over a broad range against Klebsiella Pneumoniae and Pseudomonas aeruginosa.
关键词： CdSe/CdS/ZnS,Photoluminescence,Polymer capping,Quantum dots,Antibacterial activity
更新于2025-09-23 15:19:57
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Quantification of the Photon Absorption, Scattering, and On-resonance Emission Properties of CdSe/CdS Core/Shell Quantum Dots: Effect of Shell Geometry and Volumes
摘要： Reliable quantification of the optical properties of fluorescent quantum dots (QDs) is critical for their photo-chemical, -physical, and -biological applications. Presented herein is the experimental quantification of photon scattering, absorption, and on-resonance-fluorescence (ORF) activities of CdSe/CdS core/shell fluorescent QDs as a function of the shell sizes and geometries. Four spherical QDs (SQDs) with different diameters and four rod-like QDs (RQDs) with different aspect ratios (ARs) have been analyzed using UV-vis, fluorescence, and the recent polarized resonance synchronous spectroscopic (PRS2) methods. All quantum dots are simultaneous absorbers and scatterers in the UV-vis wavelength region, and they all exhibit strong ORF emission in the wavelength regions where the QDs both absorb and emit. The absorption and scattering cross-sections of the CdS shell are linearly and quadratically, respectively, proportional to the shell volume for both the SQDs and RQDs. However, the effects of CdS shell coating on the core optical properties are different between SQDs and RQDs. For RQDs, increasing the CdS shell volume through the length elongation has no effect on either the peak wavelength or intensity of the CdSe core UV-vis absorption and ORF, but it reduces the QD fluorescence depolarization. In contrast, increasing CdS shell volume in the SQDs induces red-shift in the CdSe core peak UV-vis absorption and ORF wavelengths, and increases their peak cross-sections, but it has no effect on the SQD fluorescence depolarization. The RQD ORF cross-sections and quantum yields are significantly higher than their respective counterparts for the SQDs with similar particle sizes (volumes). While these new insights should be significant for the QD design, characterization, and applications, the methodology presented in this work is directly applicable for quantifying the optical activities of optically complex materials where the common UV-vis spectrometry and fluorescence spectroscopy are inadequate.
关键词： quantum dots,CdSe/CdS,photon absorption,shell geometry,scattering,shell volumes,on-resonance fluorescence
更新于2025-09-19 17:13:59
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CdSe@CdS Dot@Platelet Nanocrystals: Controlled Epitaxy, Mono-Exponential Decay of Two-Dimensional Exciton, and Non-Blinking Photoluminescence of Single Nanocrystal
摘要： Wurtzite CdSe@CdS dot@platelet nanocrystals—a dot-shaped CdSe nanocrystal encased within an epitaxially-grown CdS nanoplatelet—are controllably synthesized with nearly monodisperse size/shape distribution and outstanding photoluminescence (PL) properties. The excellent size/shape control with their lateral to thickness dimension ratio up to 3 to 1 is achieved by systematically studying the synthetic parameters, which results in a simple, tunable yet reproducible epitaxy scheme. This special type of core/shell nanocrystals possess two-dimensional emission dipole with the ab plane of the wurtzite structure. While their near-unity PL quantum yield and mono-exponential PL decay dynamics are at the same level of the-state-of-art CdSe/CdS core/shell nanocrystals in dot shape, CdSe@CdS dot@platelet nanocrystals possess ~2 orders of magnitude lower probability for initiating PL blinking at single-nanocrystal level than the dot-shaped counterparts do.
关键词： dot@platelet nanocrystals,non-blinking,photoluminescence,CdSe@CdS,epitaxy
更新于2025-09-19 17:13:59
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Oxygen Stabilizes Photoluminescence of CdSe/CdS Core/Shell Quantum Dots via Deionization
摘要： By taking advantage of well-defined spectroscopic signatures of high-quality CdSe/CdS core/shell QDs, effects of oxygen on photoluminescence (PL) of QDs were studied systematically and quantitatively at both single-dot and ensemble (on substrate and in solution) levels, which reveals a unified yet simple picture. With a sufficient amount of oxygen in the system during photo-excitation, the core/shell QDs in all forms would be deionized timely from the photo-generated and inefficient trion state back to efficient single-exciton state, with superoxide radicals as the reduction product of oxygen. Under a given excitation power, rates of both spontaneous deionization and photo-deionization channels increased by increasing the oxygen pressure, but photo-ionization of the QDs was barely affected by the oxygen pressure. While stabilizing PL by oxygen was identified for both CdSe plain core and CdSe/CdS core/shell QDs, irreversible photo-corrosion was only observed for CdSe plain core QDs, suggesting importance of high-quality epitaxial shells for QDs in various applications.
关键词： CdSe/CdS,superoxide radicals,oxygen,deionization,photoluminescence,quantum dots
更新于2025-09-19 17:13:59
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Nonvolatile Resistive Switching Memory Device Employing CdSe/CdS Core/Shell Quantum Dots as an Electrode Modification Layer
摘要： Accompanied with great advantages in various fields of performance, memristors show huge potential in the next generation of mainstream storage devices. However, their random distribution of resistance switching voltage has always been one of the problems in applications. In this present work, a nonvolatile resistive switching memory device was proposed, which employed CdSe/CdS core/shell quantum dots (QDs) assembled as an electrode modification layer with the device configuration of Pt/CdSe-CdS QDs/TaOx/Ta. The device possesses multiple excellent resistance switching characteristics such as lower and more consistent set/reset threshold voltage and better endurance performance, which is considered as the effect of the electrode modification layer based CdSe/CdS core/shell QDs. A model with uneven QDs/Pt electrode interface was put forward to explain the different resistance switching behaviors, which may be beneficial to the development of existing research about memristors based on metal oxides and quantum dots.
关键词： Migration,Oxygen vacancy,Schottky interface,CdSe/CdS core/shell quantum dots,resistive switching
更新于2025-09-19 17:13:59
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High efficient light-emitting diodes with improved the balance of electron and hole transfer via optimizing quantum dot structure
摘要： Modifying the structure of quantum dots (QDs) is regarded as one of the promising way to improve the charge transfer balance of quantum dot light-emitting diodes (QLEDs). In this paper, we report highly bright Cd0.1Zn0.9S/CdSe/CdS quantum dots by optimizing the CdSe shell and CdS outer shell and explore their application in QLEDs. We ?nd that with appropriate thicknesses of CdSe and CdS shell the charge transfer balance of the device can be improved. Comparable studies on two red QLEDs with Cd0.1Zn0.9S/CdSe/CdS and CdSe/CdS show that the external quantum e?ciency (EQE) of the Cd0.1Zn0.9S/CdSe/CdS device is over 3 folds higher than its counterpart, implying that structure of the QDs plays an important role in controlling the charge transfer balance of the QLEDs.
关键词： quantum dots,external quantum efficiency,QLEDs,charge transfer balance,Cd0.1Zn0.9S/CdSe/CdS
更新于2025-09-16 10:30:52
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Electronic coupling in colloidal quantum dot molecules; the case of CdSe/CdS core/shell homodimers
摘要： Coupled colloidal quantum dot molecules composed of two fused CdSe/CdS core/shell sphere monomers were recently presented. Upon fusion, the potential energy landscape changes into two quantum dots separated by a pretuned potential barrier with energetics dictated by the conduction and valence band offsets of the core/shell semiconductors and the width controlled by the shell thickness and the fusion reaction conditions. In close proximity of the two nanocrystals, orbital hybridization occurs, forming bonding and antibonding states in analogy to the hydrogen molecule. In this study, we examine theoretically the electronic and optical signatures of such a quantum dot dimer compared to its monomer core/shell building-blocks. We examine the effects of different core sizes, barrier widths, different band offsets, and neck sizes at the interface of the fused facets on the system wave-functions and energetics. Due to the higher effective mass of the hole and the large valence band offset, the hole still essentially resides in either of the cores, breaking the symmetry of the potential for the electron as well. We found that the dimer signature is well expressed in a red shift of the band gap both in absorption and emission, in slower radiative lifetimes and in an absorption cross section which is significantly enhanced relative to the monomers at energies above the shell absorption onset, while remains essentially at the same level near the band-edge. This study provides essential guidance to predesign of coupled quantum dot molecules with specific attributes which can be utilized for various new opto-electronic applications.
关键词： optical signatures,CdSe/CdS core/shell,electronic coupling,colloidal quantum dot molecules,quantum dot dimer
更新于2025-09-12 10:27:22
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Low‐Threshold Amplified Spontaneous Emission and Lasing from Thick‐Shell CdSe/CdS Core/Shell Nanoplatelets Enabled by High‐Temperature Growth
摘要： Colloidal semiconductor nanoplatelets (NPLs) have recently emerged as highly promising optical gain medium because of their superior optical properties. Here, the shell-thickness-dependent optical gain properties of CdSe/CdS core/shell NPLs synthesized by high-temperature growth are systematically investigated for the first time. The core/shell NPLs show the increased quantum yields and enhanced photostability as well as clear reduced emission blinking, thanks to the preferable passivation of nonradiative surface defects by the growth of the high-quality CdS shells under high reaction temperature. Meanwhile, the amplified spontaneous emission (ASE) performance of CdSe/CdS NPLs indicates a nonmonotonic dependence on the shell thickness. The ASE threshold is achieved as low as ≈4.4 μJ cm?2 for thick-shell NPLs with six monolayer CdS shells, and exhibiting ultrafast transient dynamics process (≈11 ps). Besides, an extremely long lifetime (>800 ps) and large bandwidth (>140 nm) of optical gain are observed by employing ultrafast transient absorption spectroscopy. Finally, a thick-shell NPLs vertical cavity surface-emitting laser is developed, which demonstrates spatially directional single-mode operation with an ultralow lasing threshold of ≈1.1 μJ cm?2. These excellent results are attributed to the remarkable optical gain performance of core/shell NPLs and represent an important step toward practical NPL laser devices.
关键词： CdSe/CdS,amplified spontaneous emission,nanoplatelets,vertical cavity surface-emitting laser,optical gain
更新于2025-09-12 10:27:22