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PbS and PbS/CdS quantum dots: Synthesized by photochemical approach, structural, linear and nonlinear response properties, and optical limiting
摘要： In this work, PbS and PbS/CdS core–shell quantum dots (QDs) were synthesized by a new photochemical approach. Prepared QDs were characterized by means of x-ray diffraction (XRD), ?eld emission scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDAX), UV–Vis, and Z-scan analyses. Synthesized QDs were in a cubic phase with a spherical morphology, and the crystallite sizes are estimated using the strain–size method. A uniform shift of Bragg diffraction peaks and quenching (200) Bragg plane are interpreted as the growth of the CdS shell. Linear optical properties were investigated using Urbach analysis and Tauc formula. It was found that the density of states of QD conduction and valence bands are three dimensional. The estimated sizes of PbS QDs and PbS/CdS using exciton absorption peaks at room temperature are 1.8 and 2.7 nm, respectively, which are in good agreement with the strain–size plot analysis. The growth of the CdS shell resulted in a considerable decrease in the nonlinearity refractive index and a signi?cant increase in the nonlinear absorption.
关键词： PbS/CdS,photochemical synthesis,PbS,optical limiting,quantum dots,nonlinear optical properties
更新于2025-09-19 17:13:59
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Grain Boundary and Interface Passivation with Corea??Shell Au@CdS Nanospheres for Higha??Efficiency Perovskite Solar Cells
摘要： The plasmonic characteristic of core–shell nanomaterials can effectively improve exciton-generation/dissociation and carrier-transfer/collection. In this work, a new strategy based on core–shell Au@CdS nanospheres is introduced to passivate perovskite grain boundaries (GBs) and the perovskite/hole transport layer interface via an antisolvent process. These core–shell Au@CdS nanoparticles can trigger heterogeneous nucleation of the perovskite precursor for high-quality perovskite films through the formation of the intermediate Au@CdS–PbI2 adduct, which can lower the valence band maximum of the 2,2,7,7-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9-spirobifluorene (Spiro-OMeTAD) for a more favorable energy alignment with the perovskite material. With the help of the localized surface plasmon resonance effect of Au@CdS, holes can easily overcome the barrier at the perovskite/Spiro-OMeTAD interface (or GBs) through the bridge of the intermediate Au@CdS–PbI2, avoiding the carrier accumulation, and suppress the carrier trap recombination at the Spiro-OMeTAD/perovskite interface. Consequently, the Au@CdS-based perovskite solar cell device achieves a high efficiency of over 21%, with excellent stability of ≈90% retention of initial power conversion efficiencies after 45 days storage in dry air.
关键词： perovskite photovoltaic devices,interface passivation,Au@CdS,core–shell nanoparticles
更新于2025-09-19 17:13:59
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Characterisation of spectroscopic and magneto-optical faraday rotation in Mn2+- doped CdS quantum dots in a silicate glass
摘要： We demonstrate the control of CdS and Mn2+-doped-CdS Q-dots in a silicate glass for magneto-optical applications. The microstructural properties of Q-dot glasses were investigated by X-Ray diffraction (XRD), Field Emission Transmission Electron Microscopy (FETEM) and the optical properties by UV-Visible-NIR and Photoluminescence (PL) spectroscopic techniques, respectively. The FETEM of the CdS QD–glass heat treated at 600oC reveals that the size of CdS and Mn2+-doped CdS Q-dots are in the range of 4-5 nm and 5-6nm, respectively. The observed size distributions of Q-dots were in reasonable agreement with the data, derived from X-ray line broadening and estimated average Bohr radii using the UV-visible absorption data. Photoluminescence characteristics were investigated at room temperature by exciting the CdS and Mn2+-doped-CdS Q-dot glasses with a 420 nm excitation source, which yielded broad emission spectra in the visible and near-IR range (450-800nm). We observed a red shift in the emission peak with increase in the Q-dot size, controlled by heat treatment temperature range (550-600oC). The room-temperature magneto-optical Faraday rotation measurements on Q-dots glasses were carried out using magnetic field strength up to 360 mT, and observed an increase in the value of Verdet constant, from 6.2 to 12.0 degree/T-cm, when comparing undoped CdS-Q-dot glass with Mn2+-doped CdS glass. The demonstration of enhanced Verdet constant in Q-dot silicate glasses with sub-Tesla field paves the path for engineering range magneto-optical devices for photonics, spintronics and sensors applications, in which the polarisation of photons may be controlled with low-intensity magnetic field in optical waveguides.
关键词： Faraday rotation,Quantum dots CdS,Photoluminescence,Dichalcogenide glass,Magneto-optics
更新于2025-09-19 17:13:59
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Cd2SnO4/CdS/Cu2O/Ag solar cell obtained by chemical techniques
摘要： By first time Cd2SnO4/CdS/Cu2O/Ag heterojunctions were studied for their application in solar cells. The heterostructure was deposited on glass-substrate and obtained by chemical techniques: i) Cd2SnO4 as TCO by sol-gel, ii) CdS as n-layer by chemical bath deposition and iii) Cu2O as p-layer by spray pyrolysis. The thicknesses of the Cd2SnO4 and CdS layers were 290 nm and 135 nm, respectively. Different thicknesses of Cu2O (τ) were used to study the effect of this parameter on the solar cell performance (135, 185, 220, 350 and 800 nm). The best photovoltaic parameters were obtained with τ= 220 nm achieving an VOC=346 mV, JSC=1.57 mA/cm2, FF=33.4 and η=0.18 %. External quantum efficiency shows current generated at energy values below Cu2O and CdS band gaps.
关键词： Cu2O/CdS,chemical techniques,solar cell,quantum efficiency,Spray pyrolysis
更新于2025-09-19 17:13:59
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Performance of Graphenea??CdS Hybrid Nanocomposite Thin Film for Applications in Cu(In,Ga)Se2 Solar Cell and H2 Production
摘要： A graphene–cadmium sulfide (Gr–CdS) nanocomposite was prepared by a chemical solution method, and its material properties were characterized by several analysis techniques. The synthesized pure CdS nanoparticles (NPs) and Gr–CdS nanocomposites were confirmed to have a stoichiometric atomic ratio (Cd/S = 1:1). The Cd 3d and S 2p peaks of the Gr–CdS nanocomposite appeared at lower binding energies compared to those of the pure CdS NPs according to X‐ray photoelectron spectroscopy analyses. The formation of the Gr–CdS nanocomposite was also evidenced by the structural analysis using Raman spectroscopy and X‐ray diffraction. Transmission electron microscopy confirmed that CdS NPs were uniformly distributed on the graphene sheets. The absorption spectra of both the Gr–CdS nanocomposite and pure CdS NPs thin films showed an absorption edge at 550 nm related to the energy band gap of CdS (~2.42 eV). The Cu(In,Ga)Se2 thin film photovoltaic device with Gr–CdS nanocomposite buffer layer showed a higher electrical conversion efficiency than that with pure CdS NPs thin film buffer layer. In addition, the water splitting efficiency of the Gr–CdS nanocomposite was almost three times higher than that of pure CdS NPs.
关键词： cadmium sulfide,Gr–CdS,Cu(In, Ga)Se2,buffer layer,water splitting
更新于2025-09-19 17:13:59
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Self-powered, all-solution processed, trilayer heterojunction perovskite-based photodetectors
摘要： Heterostructures composed of nano-/micro-junctions, combining the excellent photon harvesting properties of nano-system and ultrafast carrier transfer of micro-system, have shown promising role in high-performance photodetectors. Here, in this paper a highly-sensitive trilayer in which the CdS nanorods (NRs) layer is sandwiched between ZnO/CsPbBr3 interface to reduce self-powered perovskite-based photodetector ITO/ZnO(70nm)/CdS(150nm)/CsPbBr3(200nm)/Au, ratio of 106 with a responsivity of 86 mA/W and a specific detectivity of 6.2×1011 Jones was obtained at zero bias under 85 μW/cm2 405 nm illumination, and its rise/decay time at zero bias is to the strong built-in potential and the internal driving electric-field, an ultra-high On/Off current 0.3/0.25 s. Therefore, the enhanced device performance strongly suggest the great potential of such the interfacial charge carriers’ recombination and the charge transport resistance, is presented. Due a kind of trilayer heterojunction devices for high-performance perovskite photodetectors.
关键词： On/Off current ratio,CdS nanorods (NRs) layer,trilayer heterojunction,specific detectivity,gradient energy alignment,Self-powered photodetector,high-performance
更新于2025-09-19 17:13:59
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Selective and Sensitive Visible-Light-Prompt Photoelectrochemical Sensor of Cu2+ Based on CdS Nanorods Modified with Au and Graphene Quantum Dots
摘要： Nowadays, increasing the risk for copper leaching into the drinking water in homes, hotels and schools has become unresolved issues all around the countries such as Canada, the United States, and Malaysia. The leaching of copper in tap water is due to a combination of acidic water, damaged pipes, and corroded plumbing fixtures. To remedy this global problem, a triple interconnected structure of CdS/Au/GQDs was designed as a photo-to-electron conversion medium for a real time and selective visible-light-prompt photoelectrochemical (PEC) sensor for Cu2+ ions in real water samples. The synergistic interaction of the CdS/Au/GQDs enabled the smooth transportation of charge carriers to the charge collector and provided a channel to inhibit the charge recombination reaction. Thus, a detection limit of 2.27 nM was obtained, which is 10,000 fold lower than that of WHO’s Guidelines for Drinking-water Quality (~30 μM). The photocurrent reduction was negligible after 30 days of storage under ambient conditions, suggesting the high stability of photoelectrode. Moreover, the real-time monitoring of Cu2+ ions in real samples was performed with satisfactory results, confirming the capability of the investigated photoelectrode as the most practical detector for trace amounts of Cu2+ ions.
关键词： Copper sensing,Photo-to-electron conversion,High stability,Photoelectrochemistry,CdS/Au/GQDs
更新于2025-09-19 17:13:59
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Photoluminescence emission from nanostructured porous preparations of CdSa??ZnTiO <sub/>3</sub> assembled nanoparticles
摘要： This study reports the structural and optical properties of CdS/ZnTiO3 nanocomposites prepared using a chemical bath and different titanate concentrations. Commercial ZnTiO3 nanoparticles were introduced into a chemical bath that had been used to produce CdS semiconductor nanoparticles (NPs). Here, the growing CdS crystallites precipitated onto the suspended zinc titanate NPs. X-ray diffraction patterns revealed that samples of CdS/ZnTiO3 nanopowders were made of cubic ZnTiO3 and hexagonal CdS wurtzite. The morphology of the particles was studied using transmission electron microscopy and scanning electron microscopy images. These images demonstrated the different characteristics of the CdS/ZnTiO3 nanocomposites and their dependence on titanate concentration when placed into the CdS-growing solution. Photoluminescence spectra showed three main emission bands for the electron transitions in the CdS/ZnTiO3 composite. This composite produced three photoluminescence bands, the intensities of which depended on composite shape, which in turn depended on the relative concentrations of CdS and ZnTiO3.
关键词： CdS/ZnTiO3 nanocomposites,transmission electron microscopy,X-ray diffraction,chemical bath,photoluminescence,scanning electron microscopy
更新于2025-09-19 17:13:59
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Stable and efficient hybrid Ag-In-S/ZnS@SiO2-carbon quantum dots nanocomposites for white light-emitting diodes
摘要： As a promising energy-saving technique, the eco-friendly and low-cost solid-state white light-emitting diodes (WLEDs) based on quantum dots (QDs) have been widely studied. Herein, a WLED device prepared by core–shell structure nanocomposites based on Ag-In-S/ZnS@SiO2 quantum dots (AIS@SiO2) and carbon quantum dots (CDs) was successfully constructed. CDs were combined onto the surface of AIS@SiO2 QDs to synthesize Ag-In-S/ZnS@SiO2-Carbon quantum dots (AIS-CDs) nanocomposites with a white-light emission, which successfully overcome the quenching effect of CDs induced by conventional aggregation. The as-prepared AIS-CDs nanocomposites presented high stability and a photoluminescence quantum yield (PLQY) of 35%. Moreover, the corresponding AIS-CDs nanocomposites-based WLEDs demonstrated the color coordinate of (0.32, 0.33), which is comparable to the pure white light (0.33,0.33); Furthermore, the luminous efficiency of the as-prepared WLEDs showed 15.1 lm W-1. These results reported herein may open up a new avenue for the development of high-performance, low-cost, and environmentally-friendly WLEDs.
关键词： WLEDs,Ag-In-S/ZnS QDs,Nanocomposites,CDs
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