Papers by Keyword: CdS

Abstract: In this work, the optical and structural properties of the modified crystalline structures of the nanostructured cadmium sulphide (CdS) semiconductor caused by doping with (Cu²⁺, Ag⁺, Au⁺) transition metal ions are studied. Using the chemical bath deposition technique, thin CdS films of good crystalline quality were deposited, which were doped in synthesis without the need for additional steps, obtaining thicknesses of around 100 nm. The chemical binding energies and their interactions of the CdS semiconductor compound with the different transition metal ions were determined by X-ray photoelectron spectroscopy. The crystalline and quality phase of the CBD-CdS thin films were determined by X-ray diffraction that were confirmed by Raman scattering, obtaining that the dominant crystalline phase is zinc blende in the (1 1 1) crystalline direction. A change in crystalline quality from monocrystalline to polycrystalline was observed by XRD in the CdS thin films doped with transition metal ions, keeping the crystalline direction (1 1 1) of the zinc blende phase of CdS as the dominant one; this crystalline behaviour was confirmed by HRTEM micrographs, in addition to the different levels of quantum confinement favoured by each transition metal incorporated into the CdS. By Raman scattering measurements, the crystalline zinc blende phase of CdS was confirmed and also allowed the analysis of the phononic interactions of the binary compound, where Raman shifts provided information on the structural quality and also confirm the effects of quantum confinement. UV-visible optical spectroscopy describes the effects of the crystalline structural modifications with blue shifts on the optical band gap energies of the evaluated CdS samples, related with the different levels of quantum confinement given by the (Cu²⁺, Ag⁺, Au⁺) transition metal dopants.

Abstract: In this work, CdS nanosheets were synthesized by microwave hydrothermal method. We used a simple synthesis method to prepare Mn₃O₄/CdS composites. The crystal phase, surface chemical component and optical properties of Mn₃O₄/CdS, Mn₃O₄ and CdS were analyzed based on the characterizations such as XRD, FT-IR, DRS and PL. Mn₃O₄/Cd composites showed obvious broadened visible-light adsorption at wavelength over 460 nm. When the mass ratio of Mn₃O₄ and CdS was 1.0%, Mn₃O₄/CdS displayed the best RhB degradation efficiency which was 22.39% higher than the pure CdS. The improved photocatalytic efficiency should be attributed to the lower photo-induced electron–hole pair recombination rate and accelerated transfer rate of photogenerated electrons based on heterojunction structure. The achievements provided new way to exploring novel CdS-based heterojunctions for decomposing organic pollutants.

Abstract: New nanocrystals (NCs) were engineered with a core/shell/shell system consisting of CdSe core/ CdTe shell/ CdS shell. The white light generation mechanism was described depending on mixing colors from the illuminated CdSe/CdTe/CdS core/shell/shell nanocrystals. The color mixed in CdSe/CdTe/CdS core/shell/shell NCs system were used to generate extreme white light when illuminated by InGaN/GaN UV LED (λ=360 nm) the core/shell/shell NCs system tuned the chromaticity coordinates to (0.332, 0.340) and increased the intensity of the emitted white light. The synthesis of the CdSe/CdTe/CdS core/shell/shell NCs were confirmed by SEM, AFM, XRD and photoluminescence (PL) experiments due to create of surface states defects information. This enhancement was recognized to the overlap of emission with the photoluminescence (PL) spectrum of CdSe/CdTe/CdS core/shell/shell NCs which indications to a cold white light generation. Current-voltage (I–V) characteristics indicate that the output current is good compared to the few voltages (6 V) used which give acceptable results to get a generation of white light.

Abstract: In this article, simulation results of novel and facilitated heterostructures of the Second Generation (2G) Thin-film Solar Cells (TFSCs): hydrogenated amorphous Silicon (a-Si:H), Cadmium Telluride (CdTe), and Copper Indium Gallium di-Selenide (Cu(In,Ga)Se₂ or CIGS) have been presented to compare their performances. The solar cells have been modeled and analyzed for investigating optimized structure with higher stabilized efficiency. Entire simulations have been accomplished using Analysis of Microelectronic and Photonic Structures – 1 Dimensional (AMPS-1D) device simulator. The thickness of the absorber layer was varied from 50 nm to 1400 nm for a-Si:H and from 50 nm to 3 μm for both CdTe and CIGS cells to realize its impact on cell performance. The utmost efficiency, η of 9.134%, 20.776%, and 23.03% were achieved at AM 1.5 (1000 W/m²) for a-Si:H, CdTe, and CIGS material cells, respectively. Lastly, the operating temperature of the three cells was varied from 280°K to 328°K to realize its effect on the cell PV performances.

Abstract: This study describes extracellular biosynthesis of cadmium sulfide quantum dots by Fusarium oxysporum f. sp. lycopersici. Mycelia was incubated with a cadmium sulfate solution at 30°C and after 12 days the mixture became yellow, then the biomass was discarded through paper filtration. The filtrate containing extracellular cadmium sulfide quantum dots displayed increased UV-Vis absorption from 300 - 500 nm and fluorescence at 520 nm which was not shown when incubated without cadmium sulfide, thus indicating the presence of biologically synthesized quantum dots. Transmission electron microscope analysis of biologically synthesized quantum dots evinced individual 2 - 6 nm diameter circular nanoparticles of uniform size. Energy dispersive spectroscopy confirmed the presence of S and Cd. Additionally, this study showed the relevance in the use of positive and negative controls when evaluating the biosynthesis of CdS quantum dots using UV-Vis and fluorescence spectrophotometry.

Abstract: A possibility to improve the quality of polycrystalline CdS thin film by Nd:YAG laser irradiation was shown. The CdS thin film was prepared by closed space sublimation method on ITO/glass structure and irradiated by Nd:YAG laser with intensity up to 15 MW/cm². Several evidences demonstrated the improvement of the optical properties of the CdS thin film after the laser radiation: appearance of photoluminescence band at ~2.530 eV, which is attributed to bound exciton emission; appearance of “spike” in the reflection spectrum at ~2.573 eV between upper and lower polariton branches and the increase intensity of LO phonon line at 305 cm^-1 about 3 times in Raman back scattering spectra. Moreover, the increase by 20% of the size of crystals in CdS after laser radiation takes place, which was proved by using X-Ray diffraction analysis.

Abstract: Cu₂Zn_1-xCd_xSnS₄ pentrary alloys nanostructures have been grown on glass substrate using sol-gel technique. The concentration of Cd has showed obvious effect for structural properties. X-ray diffraction (XRD) measurements have proved nanoscale nature of the utilized alloys. The stiffness has been calculated using specific model of bulk modulus as a function of Cd concentration. The obtained results give good comparison with the experimental and theoretical data.

Abstract: Cadmium sulfide (CdS) were synthesised directly in the active layer of solar cell by mixing regioregular poly (3-hexylthiophene-2,5-diyl) or P3HT with stearic acid, and exposed to hydrogen sulfide gas. The exposure times to hydrogen sulfide gas were varied and the isotherm of P3HT:Stearic acid obtained show that the presence of cadmium ions in the subphase changes the gas-liquid-solid transformation profile. UV-Vis-NIR results indicated that exposure to hydrogen sulfide gas created CdS particles resulting in wider absorption spectra. The exposed P3HT:SA active layer exhibit high resistance that affects short circuit current density and open circuit voltage of the solar cells device. Keywords: CdS, P3HT, Thin Film, Angle Lifting Deposition, Solar Cells

Abstract: This article presents a simple method for fabrication of Au-CdS composite thin films onto indium-tin-oxide (ITO) coated glass substrates. The method starts with electrodeposition of CdS thin films onto ITO substrates and followed by spontaneous growth of Au nanoparticles onto the CdS surface in solutions containing AuCl₄^- ions. X-ray diffraction (XRD) and UV-vis spectroscopy were used to investigate the Au-CdS thin films. The photoelectrochemical property and sensing for Hg²⁺ ions of the Au-CdS/ITO were studied. The electrode exhibits a low limit of detection of 2.5 μM and a high selectivity for Hg²⁺ ions, even in the presence of a large excess (1000-fold) of other metal (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cd²⁺, Pb²⁺, and Zn²⁺) ions.

Abstract: Recently, we considered the application of carbon nanotubes as the buffer layer between the CdS and Cu (In,Ga)Se₂ thin film solar cells. In this work the structure of a p-n heterojunction solar cell is analyzed including the single walled carbon nanotubes as the absorber and CdS as n-type semiconductor window layer. The interface and current-voltage characteristics of this proposed structure are studied exerting the general formulation of the p-n heterojunction solar cells proposed by Fonash. We propose that SWCNTs/CdS heterojunction solar cell can overlap with a main part of the sunlight spectrum leading to improve efficiency and short circuit current. The interesting property of such devices is that the light can inter to the device from the absorber as carbon nanotubes are transparent semiconductor nanostructures. The results of this study can be extended to graphene nanolayers as it has been extensively studied by the PV community in recent years.