CdS Nanocrystallites Research Articles

Photovoltaic Cell Prepared from Nanoparticles of CdS/CdTe on ITO Substrate and its Characterization

CdS/CdTe based photovoltaic cell has shown the markable efficiency. The CdS/CdTe nanoparticles are being synthesized and deposited on the ITO glass plate. ITO glass has a large bandgap of about approximately 3.6 eV and is suitable to use in the fabrication of photovoltaic cell. As ITO behaves as negative terminal, it is used as front layer for capturing the light intensity. During fabrication of photovoltaic cell, the deposition of Cadmium sulphide and Cadmium telluride nanoparticles layer was done by brush painting technique. The CdS layer is used as window layer and CdTe acts as absorbing layer. The window layer’s primary function is to absorb light particularly in the visible region of the spectrum to generate electricity. The CdS layer forms p-n junction with the CdTe layer. The nanoparticles of CdS and CdTe have been synthesized first and optical characterization was carried out using UV-visible spectroscopy to obtain bandgap of CdTe and CdS. Structural characterization was being obtained by XRD. The size of the nanocrystallites of CdS and CdTe have been obtained by Debye Scherrer equation and the result was 1.64 nm and 4.09 nm respectively. The CdTe layer which was used as absorbing layer consists of high optical absorption coefficient with high mobility, good carrier lifetime and an enhanced properties of crystallographic. Silver paste was used as a back contact for good conduction.

CdS nanocrystallites sensitized ZnO nanosheets for visible light induced sonophotocatalytic/photocatalytic degradation of tetracycline: From experimental results to a generalized model based on machine learning methods

CdS/ZnO nanosheets heterostructures ((x)CdS/ZNs) with different mole ratios of Cd/Zn ((x) = 0.2, 0.4, and 0.6) were synthesized by the impregnation-calcination method. PXRD patterns showed that the (100) diffraction of ZNs was the most significant in the (x)CdS/ZNs heterostructures, and it confirmed that CdS nanoparticles (in cubic phase) occupied the (101) and (002) crystal facets of ZNs with hexagonal wurtzite crystal phase. UV–Vis DRS results indicated that CdS nanoparticles decreased the band gap energy of ZNs (2.80–2.11 eV) and extended the photoactivity of ZNs to the visible light region. The vibrations of ZNs were not observed clearly in the Raman spectra of (x)CdS/ZNs due to the extensive coverage of CdS nanoparticles shielding the deeper-laying ZNs from Raman response. The photocurrent of (0.4) CdS/ZNs photoelectrode reached 33 μA, about 82 times higher than that for ZNs (0.4 μA, 0.1 V vs Ag/AgCl). The formation of an n-n junction at the (0.4) CdS/ZNs reduced the recombination of electron-hole pairs and increased the degradation performance of the as-prepared (0.4) CdS/ZNs heterostructure. The highest percentage removal of tetracycline (TC) in the sonophotocatalytic/photocatalytic processes was obtained by (0.4) CdS/ZNs under visible light. The quenching tests showed that O2•-, h+, and OH• were the main active species in the degradation process. The degradation percentage decreased negligibly in the sonophotocatalytic (84%–79%) compared to the photocatalytic (90%–72%) process after four re-using runs due to the presence of ultrasonic waves. For the estimation of degradation behavior, two machine learning methods were applied. The comparison between the ANN and GBRT models evidenced that both models had high prediction accuracy and could be used for predicting and fitting the experimental data of the %removal of TC. The excellent sonophotocatalytic/photocatalytic performance and stability of the fabricated (x)CdS/ZNs catalysts made them promising candidates for wastewater purification.

Slow Photon-Enhanced Heterojunction Accelerates Photocatalytic Hydrogen Evolution Reaction to Unprecedented Rates

Slow Photon-Enhanced Heterojunction Accelerates Photocatalytic Hydrogen Evolution Reaction to Unprecedented Rates

Electrically activated chemical bath deposition of CdS on carbon nanotube arrays

Electrically stimulated depositions of CdS nanoparticles on the surface of aligned multi-walled carbon nanotube (CNT) arrays were investigated by applying a voltage of 3 V to the electrodes placed into a chemical bath with an aqueous ammonium solution of CdCl2 and thiourea. The CNT arrays were fixed on positive, negative, and neutral electrodes. Morphology, composition and structure of CdS-CNT hybrids were studied using scanning electron microscopy, Raman scattering and X-ray photoelectron spectroscopy. CdS nanocrystallites in the hybrids were found to exhibit synthesis-dependent luminescence properties. S-vacancy enriched CdS grown on the positively charged CNT array possessed red photoluminescence (PL). Purple emission was attributed to small-size CdS nanocrystals synthesized on the negatively charged CNTs. The CNT array located on a neutral electrode was uniformly covered by CdS nanoparticles with a highly intense blue PL. Our results indicate a promising effect of the electrical field for enhancement of the growth rate of CdS nanocrystals.

Fabrication, characterizations, and electron transportation from CdS/Cd/Si heterojunctions by the radio frequency magnetron sputtering method

CdS/Cd/Si heterojunctions have been prepared through depositing cadmium nanocrystallites (nc-Cd) and CdS nanocrystallites in turn on the single-crystal silicon wafer by the radio frequency (RF) magnetron sputtering method, which structures have been investigated by XRD and SEM techniques. Moreover, the dark/light current density vs voltage (I–V) and the impedance spectroscopy have been recorded to study the roles of incorporated nc-Cd in the electron transportation. The introduction of nc-Cd into the heterojunctions interface is helpful for the electron transportation at forward voltage. After nc-Cd has been introduced into the interface, the relaxation time, short-circuit current density, and energy conversion efficiency have been enhanced. Those are ascribed to the reduction of the defect concentration due to the introduction of nc-Cd into the interface of CdS/Si heterojunctions.

Structure transition and photoluminescence of CdS/Si nanoheterostructure array on thermal annealing

CdS/Si heterojunctions have been prepared through growing CdS nanocrystallites (nc-CdS) on the silicon nanoporous pillar array (Si-NPA) by the chemical bath deposition method. Cadmium nanocrystallites (nc-Cd) have been observed and ascribed to the reducibility of Si-NPA. The reason for the appearance of CdO is indistinct and the related work will be done in the future. The blue, green and red emissions are ascribed to the silicon oxide layer, band gap of nc-CdS and the sulphur vacancies, respectively. Redshift and blueshift with the annealing temperature about green emissions are contributed to quantum size effect and the structure transition from nc-Cd to CdO. It is beneficial for investigating the structures and defects to the application of CdS/Si in the optoelectronic field.

CdS nanocrystallites sensitized ZnO nanorods with plasmon enhanced photoelectrochemical performance

A novel architecture of CdS/ZnO nanorods with plasmonic silver (Ag) nanoparticles deposited at the interface of ZnO nanorods and CdS nanocrystallites, was designed as a photoanode for solar hydrogen generation, with photocurrent density achieving 4.7 mA/cm2 at 1.6 V (vs. RHE), which is 8 and 1.7 times as high as those of pure ZnO and CdS/ZnO nanorod films, respectively. Additionally, with optical absorption onset extended to ∼660 nm, CdS/Ag/ZnO nanorod film exhibits significantly increased incident photo-to-current efficiency (IPCE) in the whole optical absorption region, reaching 23.1% and 9.8% at 400 nm and 500 nm, respectively. The PEC enhancement can be attributed to the one-dimensional ZnO nanorod structure maintained for superior charge transfer, and the extended visible-light absorption of CdS nanocrystallites. Moreover, the incorporated plasmonic Ag nanoparticles could further promote the interfacial charge carrier transfer process and enhance the optical absorption ability, due to its excellent plasmon resonance effect.

Fabrication and electrical properties of (0 0 2)-oriented grown CdS/Si heterojunctions by radio frequency magnetron sputtering

CdS/Si heterojunctions have been fabricated through depositing (002)-oriented grown CdS on the silicon by using a radio frequency (RF) magnetron sputtering. With increasing deposition times, CdS nanocrystallites are gradually growing. Through analyzing the current density vs voltage characterization, CdS/Si heterojunctions show the rectification effect. The onset voltages, series resistances and ideality factors are heightened with increasing deposition times. However, the reverse current densities are decreasing. For all obtained CdS/Si heterojunctions, the ideality factors are far greater than 1. It is indicated that there are a lot of defects in these heterojunctions. It is believed that through optimizing the fabrication conditions the devices based on CdS/Si heterojunctions will be promising application in the field of optoelectronic devices.

Improvement and mechanisms of carriers transportation from the interfaces incorporated by cadmium nanocrystallites in the CdS/Si nanoheterojunctions

The defect states in the interface of nanoheterojunctions can trap the separated carriers and reduce the device performance. The approach through incorporating the metal nanocrystallites into the interface can enhance the local electric field to effectively separate and transport the carriers to the corresponding carrier collecting layers and decrease the recombination probability. In this paper, CdS/Si nanoheterojunctions have been fabricated through growing CdS nanocrystallites (nc-CdS) on the silicon nanoporous pillar array (Si-NPA) by using a chemical bath deposition method. Utilizing the reducibility of Si-NPA, cadmium nanocrystallites (nc-Cd) have been incorporated into the CdS-Si interface. After incorporation of nc-Cd into the interface, the forward-to-reverse current ratios, built-in potentials, short circuit current and energy conversion efficiency have been improved. It is indicated that the incorporation of nc-Cd into the interface can decrease the carrier recombination and improve the device performance. This approach will provide an meaningful idea to benefit the carrier separation and transportation, and reduce the recombination.

White light emission with tuneable colour temperature and high colour rendering index from CdS/Si multi-interface nanoheterojunctions.

CdS/Si multi-interface nanoheterojunctions (CdS/Si-NPA) were fabricated by depositing CdS nanocrystallites (nc-CdS) on silicon nanoporous pillar arrays (Si-NPA) by chemical bath deposition. White electroluminescence (EL) with a high colour rendering index from a prototypical light emitting diode based on CdS/Si-NPA has been reported, which does not need complex colour mixing or conversion techniques. The white EL can be composed into three primary colours, which include blue emissions from the Si-NPA, the green emissions from the bandgap emission of nc-CdS and red emissions from the defects in the nc-CdS. Through the annealing treatment, the chromaticity coordinate and correlated colour temperature can be tuned. This indicates that CdS/Si-NPA is a potential candidate in the one-chip white LEDs.

Synthesis and characterization of CdS nanocrystallites and OMWCNT-supported cadmium sulfide composite and their photocatalytic activity under visible light irradiation

CdS nanocrystallites and CdS- oxidized multiwalled carbon nanotubes (OMWCNT) composite were prepared by the solvothermal decomposition of a single-source molecular precursor, [Cd(pip.dtc)2] (pip.dtc = piperidine dithiocarbamate) in the presence of ethylene glycol. The as prepared CdS nanocrystallites and CdS-OMWCNT composite were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), UV-vis and Raman spectroscopy. Peak broadening in the XRD shows the formation of nanocrystalline CdS. TEM images of CdS nanocrystallites revealed the nearly spherical shape morphology of the particles, whereas, TEM images of composite showed the deposition of CdS nanocrystallites on the OMWCNT. EDX measurements matches with a 1:1 stoichiometry of Cd and S in CdS nanocrystallites, whereas, that of the composite showed the presence of Cd and S along with C. The vibrational properties of CdS nanocrystallites and their composite with OMWCNT were studied by Raman spectroscopy. Furthermore, the photocatalytic activity studies for the degradation of methylene blue under visible light irradiation using these materials were carried out. The surface area calculated using BET surface analyzer for CdS-OMWCNT composite (148.31 m2/g) was found to be more compared to bare CdS nanocrystallites (56.78 m2/g). The CdS-OMWCNT composite exhibited very good photocatalytic activity for the degradation of methylene blue under visible light irradiation which has been attributed to the increased surface area and synergistic effect in the composite compared to bare CdS nanocrystallites.

Synthesis and characterization of CdS nanoparticles decorated TiO2 matrix for an efficient N3 based dye sensitized solar cell (DSSC)

The conventional dye sensitized solar cell (DSSC) comprise of mostly the titania matrix sensitized with absorber dye molecules acting as light energy scavengers. The present investigation deals with formulating CdS–TiO2 conjugate matrix for the DSSC system using N3 dye sensitizer. TiO2 nanoparticles (NPs) were pasted on FTO glass substrate and thin film of CdS was coated on titania matrix by chemical bath deposition technique using precursors cadmium acetate and thiourea. The differential absorbance spectra of the CdS–TiO2 conjugate system shows sharp absorption edges around 345–500 nm, corresponding to band gap energies in the region 3.59 and 2.47 eV respectively, indicative of formation of two distinguishable energy region for the existence of the nano crystallites of both TiO2 and CdS. The shift in Raman bands was also observed with the incorporation of CdS in TiO2 matrix. XRD data confirms the formation of crystalline CdS nanoparticles. The FE–SEM images revealed that the TiO2 particles are spherical and monodispersed having diameter in the range 20–30 nm and embedded with CdSNPs of average particle size 10–15 nm. The performance characteristics of the synthesized films towards photovoltaic behavior were studied with the record of short circuit currents through J–V measurement using N3 absorber dye and the I−/I3 − electrolyte under 30 mW cm−2 light intensity. An effective increase of efficiency is observed with the CdS modified TiO2 matrix compared to the bare TiO2 in the DSSC system and a maximum photo-conversion efficiency of 7.5 % was obtained with the optimized dye loading. Impedance spectroscopic measurements give important information about the interfacial electron injection and recombination dynamics of the device. The incident photon-to-current conversion efficiency measurements show that both the absorbers CdS and N3 dye, contribute to the cell performance.

Constructing ternary CdS/reduced graphene oxide/TiO2 nanotube arrays hybrids for enhanced visible-light-driven photoelectrochemical and photocatalytic activity

Ternary nanocomposite photoelectrodes composed of CdS nanocrystallites, reduced graphene oxide (RGO) and TiO2 nanotube arrays (TNTs) are prepared by a coupling technique of electrophoretic deposition (EPD) and successive ionic layer adsorption and reaction (SILAR). Compare to pure TNTs, RGO/TNTs, and CdS/TNTs, the ternary CdS/RGO/TNTs hybrids show much higher visible-light-driven photoelectrochemical (PEC) and photocatalytic (PC) activity due to that the outer layer of CdS acts as sensitizer for trapping substantial photons from the visible light, the middle layer of RGO not only serves as electrons mediator and transporter for suppressing the recombination of photogenerated carriers, but also plays as a green sensitizer for enhancing visible light absorption, and the inner TNTs with narrowed band gap collect the hot electrons form the CdS and RGO to participate subsequent redox reaction for hydrogen production and organic pollutants degradation.

Thermal decomposition approach for the synthesis of CdS–TiO2 nanocomposites and their catalytic activity towards degradation of rhodamine B and reduction of Cr(VI)

CdS–TiO2 nanocomposites were prepared by a simple thermal decomposition approach. The effect of using four different types of TiO2 (as-prepared sol–gel TiO2 nanoparticles, sol–gel TiO2 after calcination at 500°C, sol–gel TiO2 after calcination at 700°C and macro-crystalline TiO2 ) on the structure, optical properties and photocatalytic activity of the nanocomposites was investigated. The nanocomposites were characterized by powder X-ray diffraction, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy, diffuse reflectance spectroscopy and photoluminescence spectroscopy. The CdS–TiO2 nanocomposites consist of cubic CdS and anatase TiO2 nanocrystallites when as-prepared sol–gel TiO2 nanoparticles, sol–gel TiO2 calcined at 500°C and macro-crystalline TiO2 were used. On the other hand, when sol–gel TiO2 after calcination at 700°C was used, the nanocomposites were found to consist of rutile TiO2. TEM results indicate uniform distribution of CdS nanoparticles (10.5±1.6nm) on the TiO2 matrix in the nanocomposites prepared using as-prepared sol–gel TiO2 nanoparticles and sol–gel TiO2 after calcination at 500°C. In the nanocomposites, a blue shift of the band gap of CdS compared to bulk CdS is observed. The CdS–TiO2 nanocomposites act as good catalyst for the photodegradation of rhodamine B (RhB) and reduction of Cr(VI) in the presence of sunlight.

A Novel Approach for the Synthesis and Characterization Studies of Mn 2 + -Doped CdS Nanocrystals by a Facile Microwave-Assisted Combustion Method

A simple and efficient microwave-assisted combustion method was developed to synthesize Mn 2+-doped CdS (Mn xCd 1−xS: x= 0.0, 0.3, and 0.5) nanocrystallites. The study suggested that the application of microwave heating produced spherical shaped cluster of pure and Mn 2+-doped CdS nanocrystallites, which was achieved in few minutes. The effects of Mn 2+-doping on structural, morphological, optical and magnetic properties of CdS nanocrystallites were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution scanning electron microscopy (HR-SEM) with energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED), UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM). The XRD results confirmed the formation of hexagonal CdS. The formation of pure and Mn 2+-doped CdS phase was also confirmed by FT-IR and EDX. The formation of spherical shaped cluster of nanocrystallites was confirmed by HR-SEM and HR-TEM. The as-synthesized nanocrystallites were found to have good optoelectronic properties that were determined by DRS and PL spectra. VSM results of the as-synthesized Mn 2+-doped CdS nanocrystallites showed ferromagnetic behavior.

Effect of interface incorporation of cadmium nanocrystallites on the photovoltaic performance of solar cells based on CdS/Si multi-interface nanoheterojunction

A non-planar and multi-interface CdS/Si nanoheterojunction was prepared by growing CdS nanocrystallites (nc-CdS) onto silicon nanoporous pillar array (Si-NPA) using a chemical bath deposition (CBD) method. Utilizing the surface reducibility of Si-NPA, small quantities of Cd nanocrystallites (nc-Cd) were incorporated naturally into the CdS–Si interface during the CBD process. Solar cells with a device construction of ITO/CdS/Si-NPA/Al were prepared based on CdS/Si-NPA and their photovoltaic performances, including open circuit voltage, short circuit current density, external quantum efficiency and energy conversion efficiency, were measured under simulated AM 1.5G illumination. Compared with CdS/Si-NPA cells without nc-Cd incorporation, an energy conversion efficiency promotion by two orders of magnitude was achieved, which was ascribed to the reduction of the series resistance resulted from the nc-Cd incorporation at the interface. Our results show that the incorporation of nc-Cd at CdS–Si interface might be an effective path for obtaining high-efficiency solar cells based on CdS/Si multi-interface nanoheterojunctions.

Enhanced photoluminescence from ordered arrays of cadmium sulfide nanotubes synthesized using nanoscale chemical reactors.

We report enhanced room temperature photoluminescence from ordered arrays of few micrometers long cadmium sulfide nanotubes fabricated using 'nanoscale chemical reactors' of porous alumina by a unique two-chamber synthesis without using any surfactants. Photoluminescence from these nanotubes is -20 times larger than that of nanocrystalline cadmium sulfide particles prepared by bulk mixing of the same reactants. However, we rule out any quantum size effect as a source of enhanced photoluminescence from these intentionally un-passivated nanotubes. We identify sulfur deficiency in these nanotubes and directional orientation of these ordered nanotube arrays as the main reason for its superior photoluminescence as compared to agglomerated nanocrystallites of CdS prepared by bulk mixing.

Structural and Spectroscopic Studies of Sm3+/CdS Nanocrystallites in Sol–Gel TiO2-ZrO2 Matrix

A sol–gel method was used to prepare titania-zirconia matrices doped with Sm3+/CdS nanocrystallites. The structural properties of the matrices were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier-transform infrared spectroscopy studies. The thermal stability of the material was determined by TGA/DTA analysis. The absorption spectrum shows the characteristic peaks of the Sm3+ ions and the absorption peak corresponding to the CdS nanocrystallites. The optical bandgap and size of the CdS nanoparticles were calculated from the absorption spectrum. From TEM, the interplanar distance (d) was estimated to be 3.533 A, which matches with the (1 0 0) plane of bulk CdS. The measurements yield a nanocrystallite size of around 7.8 nm. The optical absorption and emission spectra confirmed the formation of CdS nanoparticles along with samarium ions in the titania-zirconia matrices. The fluorescence intensity of the samarium ions was found to be greatly enhanced by codoping with CdS nanocrystallites.

A simple route in the synthesis of CdS nanoparticles

A simple route in the synthesis of CdS nanoparticles (cubic-type) is presented. The synthesis is based on the reaction of H2S gas with a 10% aqueous solution of Cd(CH3COO)2 at room temperature The XRD pattern showed very broadened diffraction lines. The presence of CdS nanocrystallites 2–3nm in size was estimated by the Scherrer method. The CdS nanoparticles were characterized by Raman and UV/vis spectroscopies. The FE-SEM image showed the formation of uniform CdS nanoparticles with an average size ∼20–25nm, thus indicating that these nanoparticles consisted of very fine CdS nanocrystallites.

Synthesis and X-ray single crystal structure of a cadmium(II) acetophenone thiosemicarbazone complex and its use as a single-source precursor for the preparation of CdS nanocrystallites and thin films

A cadmium(II) acetophenone thiosemicarbazone complex has been prepared and characterized by elemental analysis, infrared and nuclear magnetic resonance (1H and 13C{1H}) spectroscopic techniques. Its single crystal structure has also been determined. The compound is found to be monoclinic, space group C2/c, with a=12.1020(3)Å, b=11.7410(3)Å, c=19.4050(8)Å, β=109.903(1)° and Z=4. The coordination geometry around the cadmium atom was found to be tetrahedral with coordination from two sulfur atoms of neutral ligands and two iodine atoms. The complex was exploited as a single source precursor for the synthesis of CdS nanocrystallites using the solvothermal decomposition and pyrolysis method and for thin films using the aerosol assisted chemical vapor deposition technique. In the solvothermal process, aliquots of the reaction mixture were taken out after 30min, 1, 2 and 5h time intervals to study the time dependent size and morphology of the nanomaterials. The obtained nanomaterials and thin films were characterized by powder X-ray diffraction, transmission electron microscopy, energy dispersive X-ray analysis, selected area electron diffraction pattern, UV–Vis, Photoluminescence, IR and Raman spectroscopy. Peak broadening in the X-ray diffraction showed the presence of smaller size CdS nanocrystals. Transmission electron microscopy images showed the presence of spherical shaped CdS nanocrystallites. Selected area electron diffraction pattern supported formation of hexagonal CdS. Energy dispersive X-ray analysis showed a 1:1 stoichiometry of Cd and S. Morphological studies of thin films were carried out using scanning electron microscopy and atomic force microscopy techniques. The vibrational properties of CdS were studied by Raman spectroscopy.