Band Gap Of CdS Research Articles

Surface polar charge induced Ni loaded CdS heterostructure nanorod for efficient photo-catalytic hydrogen evolution

Designing of artificial heterostructure photo-catalysts to crop solar energy for H2 evolution from water is of great importance nowadays. The ultrafine Ni (0.5, 1.0, 2.0 and 5.0 wt%) particles loaded CdS nanorods were synthesized by a simple chemical process. XRD shows the crystalline phase of CdS with increase in size from 17 to 28 nm with 10.19% and 10.06% enhancement in the lattice strain and the dislocation density for Ni (0.5–5.0 wt%). The XPS peaks observed at 854.88 eV and 861.07 eV for Ni2+ with energy separation of 6.18 eV confirmed the existence of NiO on Ni surface. The Raman bands for pure CdS and Ni (1.0 wt%)-CdS nanorods were observed at 300 cm−1 and 293 cm−1 for 1LO phonon and 601 cm−1 and 586 cm−1 for 2LO phonon, respectively. The Ni loading tuned the CdS band gap from 2.36 to 2.20 eV. The eight fold enhancement in the CdS specific surface area i.e., from 4.19194 m2 g−1 to 34.8343 m2 g−1 was achieved. After Ni loading, the synergetic effect of efficient electron separation and transportation was observed by the continuous quenching of luminescence emission intensity and the reduction of charge transfer resistance from 706 Ω for CdS to 484 Ω of CdS. The Ni (1.0 wt%)@ NiO optimal loading on CdS results highest photo-catalytic H2 evolution of 9.0 mmol at rate of 1.8 mmol h−1, which is about 50 times higher than that of 180 μmol at rate of 36 μmol h−1 for pure CdS. A thin layer of NiO on plasmonic Ni surface could be the promising system for photo-catalytic H2 evolution due to visible light photo-activity.

Band structure and enhanced photocatalytic degradation performance of Mg-doped CdS nanorods

Abstracts In this paper, Mg-doped CdS nanorods (MgCdS) were prepared by a simple solvothermal method to investigate the band structure and enhanced photocatalytic degradation performance under visible light illumination. Mg element is successfully doped into the lattice of CdS and it doesn't destroy the nanorod structure of CdS. The band gap of CdS is widened by Mg doping. The prepared MgCdS shows improved photocatalytic degradation performance than CdS, and 5% MgCdS has the optimal photocatalytic degradation performance, which can degrade approximately 96% RhB in 70-min visible light illumination. The enhanced photocatalytic degradation performance of 5% MgCdS is due to the increased photogenerated charge carrier concentration and the effectively suppressed recombination of photogenerated carriers.

Cd-Free Zn(O,S) as Alternative Buffer Layer for Chalcogenide and Kesterite Based Thin Films Solar Cells: A Review.

Cd is categorized as a toxic material with restricted use in electronics as there are inherent problems of treating waste and convincing consumers that it is properly sealed inside without any threat of precarious leaks. Apart from toxicity, band-gap of CdS is about 2.40-2.50 eV, which results significant photon loss in short-wavelength range which restricts the overall performance of solar cells. Thin film of Zn(O,S) is a favorable contender to substitute CdS thin film as buffer layer for CuInGaSe₂ (CIGS), CuInGa(S,Se)₂ (CIGSSe), Cu₂ZnSn(S,Se)₄ (CZTSSe) Cu₂ZnSnSe₄ (CZTSe), Cu₂ZnSnS₄ (CZTS) thin film absorber material based photovoltaic due to it made from earth abundant, low cost, non-toxic materials and its ability to improve the efficiency of chalcogenide and kesterite based photovoltaic due to wider band-gap which results in reduction of absorption loss compared to CdS. In this review, apart from mentioning various deposition technique for Zn(O,S) thin films, changes in various properties i.e., optical, morphological, and opto-electrical properties of Zn(O,S) thin film deposited using various methods utilized for fabricating solar cell based on CIGS, CIGSSe, CZTS, CZTSe and CZTSSe thin films, the material has been evaluated for all the properties of buffer layer (high transparency for incident light, good conduction band lineup with absorber material, low interface recombination, high resistivity and good device stability).

EFFECT OF Ce DOPING ON THE CHARACTERISTIC PROPERTIES OF CdS NANOPARTICLES

In our present study, Ce doped CdS nanoparticles were synthesized in room temperature environment by using chemical co-precipitation technique which is cheap in cost. Ce doped CdS nanoparticles ( average particle size: 3.7 nm) were found to have cubic structure as a result of XRD measurements. It has also been clearly observed that Ce dopant ions do not alter the structure of the host semiconductor CdS. Using the spectrum obtained as a result of UV-Vis measurement, the energy band gap of Ce doped CdS nanoparticles was determined as 2.73 eV. This value was observed to be higher than the energy band gap of bulk CdS (2.42 eV). Thus, it can be said that this change in the energy band gap is due to the quantum confinement effect. The maximum IPCE value was 27% for Ce doped CdS nanoparticles while the IPCE values was 4% for pure CdS nanoparticles, respectively. The IPCE of the solar cells improves with the Ce dopant ion. Moreover, the spectral response range of Ce doped CdS nanoparticles widens with the Ce dopant ion. This is attributed to the long lifetimes of the Ce3+ excited states that facilities the transfer of the charge carries to the photoelectrode.

Performance of Graphene-CdS Hybrid Nanocomposite Thin Film for Applications in Cu(In,Ga)Se2 Solar Cell and H2 Production.

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.

Original signal amplification assay for N-Terminal pro-brain natriuretic peptide detection based on Bi2MoO6 photosensitive matrix

An original dual signal amplification immunoassay for N-Terminal pro-brain natriuretic peptide (NT-proBNP) detection is developed based on Au NPs and Zn doped CdS nanoparticles (Zn0.02Cd0.98S) co-sensitized Bi2MoO6 nanosheet photoelectrochemical (PEC) platform, the target is a good myocardial marker for diagnosing heart failure (HF). Bi2MoO6 as an outstanding photocatalysis material is successfully used in PEC analysis in this work, and the nanosheet structure provide a preponderance to capture superior Zn0.02Cd0.98S in order to achieve anticipant PEC response. The doping of Zn makes the energy band of CdS matched more compatible with Bi2MoO6, and improves the narrow band gap of CdS, making the surface plasma resonance (SPR) effect of Au NPs more significant, thus further improving the PEC response, as well as elevated the detection sensitivity of biological targets. The constructed PEC platform for NT-proBNP provides a wide detection range of 0.0001–1000 ng mL−1 and gives the minimum detection value of 0.037 pg mL−1. Great stability, high selectivity, and good reproducibility are also achieved. The proposed PEC immunoassay provides more possibilities for other protein ultra-sensitivity detection.

Highly luminescent double-heterojunction nanorods.

Anisotropic shape and band structure engineered into double-heterojunction nanorods (DHNRs) can improve and impart new optical/optoelectronic capabilities in colloidal quantum dot-based devices. However, the photoluminescence quantum yield of DHNRs, which is significantly lower than the near-ideal limit recently achieved in the state-of-the-art core/shell quantum dots, remains as their main limitation. Here, we examine how the photoluminescence of CdS/CdSe/ZnSe DHNRs is affected by (1) the length of the CdS seed nanorods, (2) the rod and tip diameter dependent variations in band offset, and (3) the CdSe-like islands on the sides of DHNRs that can result as a side-product of ZnSe shell growth. By understanding and optimizing these three key parameters, we demonstrate an improvement in the photoluminescence quantum yield up to 93% (up to 62% for excitation above CdS bandgap) while retaining useful shape anisotropy and the band structure design in DHNRs.

Ternary system from mesoporous CdS–ZnS modified with polyaniline for removal of cationic and anionic dyes

In this work, mesoporous CdS (130.7 m2/g) was prepared; then, ZnS was deposited by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR) method, to get CdS–ZnS(C) and CdS–ZnS(S), respectively. Subsequently, the highest efficient binary hybrid was sensitized with polyaniline to produce CdS–ZnS–PANI for the first time. XRD and EDX analyses confirmed the coating of CdS with ZnS using CBD and SILAR method. The careful examination for the surface morphology of the binary hybrids illustrated that CdS–ZnS(S) has uniform morphology and the CdS nanoparticles are homogeneously overcoated with ZnS. In contrast, CdS–ZnS(C) exhibits inhomogeneous surface, where there are ZnS particles that aggregate together and there is another region which contains ZnS deposited onto CdS. The estimated band gap of CdS, CdS–ZnS(S), and CdS–ZnS–PANI was 2.36 eV, 2.44 eV, and 1.9 eV, respectively. The removal efficiency for cationic and anionic dyes single and/or in combination using CdS, ZnS, CdS–ZnS(C), CdS–ZnS(S), PANI, and CdS–ZnS–PANI was studied. The effect of the amount of ZnS loaded by SILAR process on the activity of the CdS–ZnS(S) was presented. The results proposed that CdS–ZnS(S) exhibits selective adsorption and high removal efficiency for cationic dye compared to CdS–ZnS(C) due to higher negative zeta potential and large surface area. The CdS–ZnS–PANI ternary nanocomposite showed uptake efficiency of 96.7% for cationic dye (MB) and 94.3% for anionic dye (MO) in a mixed dye solution after 10 min. Finally, the possible adsorption mechanism was proposed.

Fluorescence Quantum Yield and Single-Particle Emission of CdSe Dot/CdS Rod Nanocrystals

The fluorescence quantum yield (QY) of CdSe dot/CdS rod (DR) nanoparticle ensembles is dependent on the Shell growth and excitation wavelength. We analyze the origin of this dependency by comparing the optical properties of DR ensembles to the results obtained in single-particle experiments. On the Ensemble level, we find that the QY of DRs with shell lengths shorter than 40 nm exhibits no dependence on the excitation wavelength, whereas for DRs with shell lengths longer than 50 nm, the QY significantly decreases for excitation above the CdS band gap. Upon excitation in the CdSe core, the ensemble QY, the fluorescence wavelength, and the fluorescence blinking behavior of individual particles are only dependent on the radial CdS shell thickness and not on the CDs shell length. If the photogenerated excitons can reach the CdSe core region, the fluorescence properties will be dependent only on the surface passivation in close vicinity to the CdSe core. The change in QY upon excitation above the band gap of CdS for longer DRs cannot be explained by nonradiative particles because the ratio of emitting DRs is found to be independent of the DR length. We propose a model after which the decrease in QY for longer CdS shells is due to an increasing fraction of nonradiative exciton recombination within the elongated shell. This is supported by an effective-mass-approximation-based calculation, which suggests an optimum length of DRs of about 40 nm, to combine the benefit of high CdS absorption cross section with a high fluorescence QY.

Effect of electrolytes on photoelectrochemical performance of a CuS–CdS heterojunction

CdS–CuS heterojunction films have been grown successfully on a copper substrate using a chemical bath deposition (CBD) method. The obtained films are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical absorption, Raman spectroscopy and photoluminescence (PL) analysis and the photo-electrochemical (PEC) properties of the CdS–CuS heterojunction have been studied using different electrolytes. The XRD pattern of CuS–CdS shows peaks corresponding to CuS (hexagonal) and CdS (cubic) structures, while the optical absorption studies revealed the presence of an absorption edge corresponding to CuS–CdS (band gap of 1.85 eV). The Raman spectra of the CuS, CdS and CuS–CdS heterojunctions were recorded and are in good agreement with the results reported in the literature. TEM and cross-sectional SEM images show an overlap between CuS rods and CdS flasks. The charge transfer across the layers was studied by using PL spectra. The measurement of the photo-electrochemical properties using a conventional two electrode system for an iodine electrolyte showed the highest conversion efficiency of 1.40% as against for potassium ferro–ferricyanide (0.38%) and polysulphide electrolytes (0.02%).

Synthesis and photocatalytic property of cubic phase CdS

In order to understand the nanostructure-based architectures and phase structures of CdS on the photocatalytic property, we have synthesized 3 D flower-like CdS with cubic phase and hexagonal phase CdS nanoparticles by hydrothermal method. The as-prepared samples have been characterized by XRD, FESEM, and UV–Vis. The photocatalytic activity has been evaluated by the photocatalytic degradation of methylene blue (MB) under simulated visible-light irradiation. FESEM results reveal that the morphologies of cubic phase CdS are flower-like structures, and the morphologies of hexagonal phase CdS are nanoparticles. The optical energy band gap of flower-like CdS is 2.25 eV from UV–Vis result. Moreover, the flower-like CdS exhibits better photocatalytic activity and its highest degradation rate to MB can reach 90.4% than that of CdS nanoparticles.

Structural and optoelectronic properties of CdS/Y/CdS thin films

In the current study, the structural, optical, photoelectrical and electrical properties of CdS/Y/CdS thin films are investigated. The current design include the evaporation of a layer of 70 nm thick yttrium between two layers of CdS. Each CdS layer is of thickness of 500 nm. It is observed that the yttrium slab increased the microstrain, defect density, stacking faults and decreased the grain size and redshifts the indirect allowed transitions energy band gap of CdS. In addition an enhancement by ~5 times in the light absorbability is detected at 1.74 eV. The enhanced absorbance results in increasing the photocurrent by ~ 21 times and changed the recombination mechanism from a trap assisted recombination to supralinear recombination mechanisms. Moreover, the ac signal analysis in the frequency domain of 10–1800 MHz has shown that the yttrium forces the CdS to exhibit negative capacitance effect and make it behave as band stop filter with notch frequency of 1520 MHz. The quality of the CdS/Y/CdS films as microwave cavities are screened by the evaluation of the return loss which revealed good features of the nanostructured films as microwave receivers.

Improved magnetic and photocatalytic properties of spray deposited (Li+Co) codoped CdS thin films

Undoped, Li-doped and (Li + Co) codoped CdS thin films were spray deposited using perfume atomizer. All the films crystallizes with hexagonal structure and they show a (0 0 2) preferential growth. The crystallite size value of pure CdS decreased with Li doping and (Li + Co) codoping. The surface morphology of pure CdS significantly modified with Li doping and (Li + Co) codoping. Nanoneedles were observed for the (Li + Co) codoped CdS thin film. The existence of the elements Cd, S, Li and Co in the codoped film was ascertained from the XPS spectra. Optical band gap of pure CdS decreased from 2.47 eV to 2.43 eV with Li doping and with Co codoping it increased to 2.51 eV. Decreased electrical resistivity was observed for the Li-doped and (Li + Co) codoped films. Improved magnetic property was observed for the (Li + Co) codoped thin film which was ascertained from the presence of well defined hysteresis loop. Photocatalytic tests showed that the (Li + Co) codoped CdS thin film exhibited a maximum photodegradation efficiency of 81.25% against metanil yellow under visible light irradiation.

Photocatalytic Performance of Cubic and Hexagonal Phase CdS Synthesized via Different Cd Sources

CdS has been widely used in photocatalysis, by virtue of its sensitivity to visible-light irradiation. But CdS has two crystalline phases, which are not equally well understood. Hence, we synthesized cubic phase and hexagonal phase hierarchical CdS with different Cd sources by the hydrothermal method. These as-prepared CdS samples were characterized by powder x-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), ultraviolet–visible spectrophotometer (UV–Vis), and room temperature photoluminescence (PL). Photocatalytic degradation of methylene blue was evaluated under simulated visible-light irradiation. PXRD results revealed that the CdS samples manifested a cubic phase when the Cd source was CdCl2, but the CdS assumed a mixed hexagonal and cubic phase when the Cd source was Cd(NO3)2. FESEM results indicate that the morphologies of CdS are both flower-like structures. The optical energy band gap of cubic phase CdS is 2.26 eV, but mixed hexagonal and cubic phase CdS is 2.24 eV according to UV–Vis results. PL results show that CdS samples of both phases have a similar emission peak near 560 nm, which is consistent with UV–Vis absorption spectrums. In addition, mixed hexagonal and cubic phase CdS exhibits better photocatalytic activity than cubic phase CdS.

The High Performance of Quantum Dot Sensitized Solar Cells Co-Sensitized with Mixed-Joint CdS and ZnS Quantum Dots

We propose a facile way to prepare CdS and ZnS quantum dots (QDs) in photoanode oxide films in quantum dot sensitized solar cells (QDSCs). CdS QDs as sunlight harvester and ZnS as passivation layer are deposited in mesoporous RGO/TiO2 (reduced graphene oxide and TiO2 composite) films alternately through successive ionic layer adsorption and reaction (SILAR) to engineer the mixed-joint CdS/ZnS QDs. For comparison, another CdS and ZnS QDs are prepared with depositing all CdS firstly and then ZnS QDs in mesoporous RGO/TiO2 films. The power conversion efficiency (PCE) of mixed-joint CdS/ZnS based cell samples improve greatly, up to 6.37%, almost two times higher than that of bare CdS based quantum dot sensitized solar cells (2.54%), and also higher than that of CdS/ZnS based QDSCs (4.12%) obviously. Since the conduction band of ZnS (bandgap, 3.6ev) is higher than that of CdS (bandgap, 2.25ev), ZnS quantum dots can suppress reversed transport of photo-excited electrons and improve the efficiency of electron collection and meanwhile, they also impede hole transfer from the valance band of CdS to electrolytes. It seems to be an optimal way to solve this contradiction when mixed-joint CdS/ZnS are used to cosensitize QDSCs due to their characteristic architecture. The mechanism of effect of ZnS QDs on the photovoltaic performance of QDSCs is investigated combined sensitized photoanode microstructural characterization and electrochemical impedance spectroscopy (EIS) and J-V curve analysis of cell samples.

Effects of CdS quantum dot in polymer nanocomposites: In terms of luminescence, optic, and thermal results

CdS quantum dots (QDs) which have unique luminescence efficiency were synthesized by two-phase method using oleic acid (OA) as a surfactant. The nanocomposites have been obtained by blended CdS quantum dots with low-density polyethylene (LDPE) in different ratios. Primarily, radioluminescence (RL) properties were investigated as well as their structural (FT-IR, XRD), morphological (TEM, SEM), thermal (TG-DTA) and absorption (UV–Vis) properties of these nanocomposites. The RL peaks of OA-capped CdS QD were observed at 456 nm and 655 nm. As a consequence of the nanocomposites being doped with powder CdS QD, a significant blue shift was observed in the absorption bands. The optical band gap of CdS was calculated as ̴ 2.3 eV. The nanocomposites blended with CdS QD, this value increased to ̴ 2.7 eV. It has also been observed that nanoparticles cause nanocomposites to have lower melting temperatures.

Temperature dependence of the band gap of high optical quality CdS:Dy thin films based on exciton spectra

CdS:Dy films were prepared by CSVS method on the cleaned glass substrates. The influence of Dy doping on the optical properties of CdS thin (500 nm) films was studied. The presence of narrow lines of bound and free excitons in the photoluminescence, reflection and absorption spectra shows a remarkable optical quality of the investigated films. The temperature dependence of the band gap of the films was studied on the basis of measurements of the energy position of the free excitons. A decrease in the anisotropic crystal field and the effect of depolarization of free exciton absorption spectra with increasing temperature are observed. It was concluded that the efficiency of CdS:Dy thin films photovoltaic applications can be further increased.

Systematic stacking of PbS/CdS/CdSe multi-layered quantum dots for the enhancement of solar cell efficiency by harvesting wide solar spectrum

Fabrication of multi-layered quantum dot sensitized solar cells, especially q-dot solar cells that contain more than two layers of q-dots as light harvesting materials is a great challenge due to adverse effects exert by the q-dots in the outer-layers on the inner optimized q-dot layer. In this work, multi-bandgap q-dots of PbS (bandgap 1.16 eV), CdS (bandgap 2.01 eV) and CdSe (bandgap1.76 eV) are stacked in different combinations on the mesoporous TiO2 layer to enhance the light harvesting ability. The problems associated with stacking of multi-layers of q-dots on the mesoporous TiO2 layer were also investigated. The observed photovoltaic properties of multiband q-dot solar cells with different stacking configurations are then compared with the optical and electrical properties of multi-band gap quantum dots. The optimized three-layer PbS/CdS/CdSe q-dot solar cell showed a solar cell efficiency of 6.2% while two-layer q-dot solar cells fabricated with PbS/CdS and CdS/CdSe showed solar cell efficiencies of 5.8 and 4.2% respectively. The enhanced solar cell performance of three-layer PbS/CdS/CdSe q-dot solar cell is found to be mainly due to proper cascade stacking of three q-dot layers in photoanode that ensuing in enhanced charge transport as well as higher light harvesting.

Properties of the CdSxTe1-x solid solution: As a single product and as a part of the CdS/CdTe solar cell

Thin film CdS/CdTe solar cells are promising candidates for large-scale photovoltaics. The CdSxTe1-x solid solution is always formed at the interface between the CdS window layer and CdTe absorber layer due to the intermixing at the interface region. It is confirmed that this interdiffusion process significantly affects the device performance. This occurs through several things of which are changing the bandgap of both CdTe and CdS, which modifies the spectral response of the solar cell, and reducing the lattice mismatch at the CdS/CdTe junction which results in the reduction of the number of interfacial states and recombination centers. This work gives a short review of the properties of this solid solution in two cases; first, when it is produced as a separate product (i.e. powder or thin films), and second when it is part of the solar cell (i.e. created due to interdiffusion or introduced as a layer between CdS and CdTe).

Indium doping on the structural, surface and optical properties of CdS thin films prepared by ultrasonic spray pyrolysis method

CdS nanostructures are important and useful materials for photovoltaic applications. In this paper, pure CdS and In doped CdS (CdS:In) thin films were fabricated on soda lime glass substrate using ultrasonic spray pyrolysis (USP) method, to investigate the effect In concentration on the structural behavior, surface and optical properties of the CdS thin films by X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Ultraviolet–visible (Uv-vis) spectrophotometry. X-ray diffraction patterns of the pure and In doped CdS films indicated that pure CdS film had a mixed of cubic and hexagonal structure with polycrystalline nature while In doped CdS had a hexagonal structure with polycrystalline nature. Increasing the In doping ratio improve the (002) preferential orientation. The optical properties of the In-doped CdS and pure CdS films showed that the energy band gap of the In-doped CdS is a slightly lower than the energy band gap of the pure CdS film. The surface properties of the films showed that all thin films are compact and uniform.