CdS Nanowires Research Articles

Hybrid solar cell on a carbon fiber.

In this work, a method to assemble nanoscale hybrid solar cells in the form of a brush of radially oriented CdS nanowire crystals around a single carbon fiber is demonstrated for the first time. A solar cell was assembled on a carbon fiber with a diameter of ~5–10 μm which served as a core electrode; inorganic CdS nanowire crystals and organic dye or polymer layers were successively deposited on the carbon fiber as active components resulting in a core-shell photovoltaic structure. Polymer, dye-sensitized, and inverted solar cells have been prepared and compared with their analogues made on the flat indium-tin oxide electrode.

Fabrication of CdS nanowires with increasing anionic precursor by SILAR method

CdS nanowires were fabricated on glass substrate at room temperature by SILAR method with cadmium nitrate cationic and sodium sulfide anionic precursors. The deposition were done at different S:Cd concentration ratios of 1:1, 3:1, 5:1, and 7:1. Nanowires growth procedure was studied in the mentioned concentrations. The number of immersion cycles was kept constant at 15 cycles. EDX analysis showed that in all stoichiometric ratios, S/Cd composition ratio remains at about unity. Our results indicated that S:Cd concentration ratio of 7:1 had the longest nanowires with hexagonal structure. The main objective of this paper was to produce CdS nanowires with increasing concentration of sulfur.

Chemiluminescent lateral-flow immunoassays by using in-situ synthesis of CdS NW photosensor

A hypersensitive CdS nanowire (NW) photosensor was fabricated by an in-situ synthesis process that involved the direct synthesis of CdS NWs on an interdigitated electrode (IDE). Analysis of the photoresponse properties showed that the newly synthesized photosensor had enhanced sensitivity and a highly reproducible photoresponse compared to photosensors prepared from CdS NW suspensions. The NW photosensor was applied to measure the chemiluminescence of luminol, and the sensitivity was compared to a commercial photosensing system. Finally, the feasibility of the CdS NW photosensor for the application to the medical diagnosis of the human hepatitis B surface antigen (hHBsAg) was demonstrated using a lateral-flow immunoassay with a chemiluminescent signal band.

Color-tunable photoluminescence from In-doped CdS nanowires

Color-tunable emission from semiconductor nanostructures holds promising applications in developing multi-color/color-tunable nano-devices. Herein, we reported the growth of In-doped CdS nanowires with various dopant concentrations via a thermal evaporation method. Optical measurement revealed the photoluminescence of these doped nanowires consists of a narrow bandedge emission and a broad trap-state emission, and the intensity ratio between them is tunable depending on excitation laser intensities and trap-state concentrations. On the basis of this variable intensity ratio, a tunable photoluminescent color from red to green was demonstrated. Our work indicates that trap-state emission from doped nanostructures might be useful for color-tunable emissions.

When Nanowires Meet Ultrahigh Ferroelectric Field-High-Performance Full-Depleted Nanowire Photodetectors.

One-dimensional semiconductor nanowires (NWs) have been widely applied in photodetector due to their excellent optoelectronic characteristics. However, intrinsic carrier concentration at certain level results in appreciable dark current, which limits the detectivity of the devices. Here, we fabricated a novel type of ferroelectric-enhanced side-gated NW photodetectors. The intrinsic carriers in the NW channel can be fully depleted by the ultrahigh electrostatic field from polarization of P(VDF-TrFE) ferroelectric polymer. In this scenario, the dark current is significantly reduced and thus the sensitivity of the photodetector is increased even when the gate voltage is removed. Particularly, a single InP NW photodetector exhibits high-photoconductive gain of 4.2 × 10(5), responsivity of 2.8 × 10(5) A W(-1), and specific detectivity (D*) of 9.1 × 10(15) Jones at λ = 830 nm. To further demonstrate the universality of the configuration we also demonstrate ferroelectric polymer side-gated single CdS NW photodetectors with ultrahigh photoconductive gain of 1.2 × 10(7), responsivity of 5.2 × 10(6) A W(-1) and D* up to 1.7 × 10(18) Jones at λ = 520 nm. Overall, our work demonstrates a new approach to fabricate a controllable, full-depleted, and high-performance NW photodetector. This can inspire novel device structure design of high-performance optoelectronic devices based on semiconductor NWs.

CdS Nanowires Decorated with Ultrathin MoS2 Nanosheets as an Efficient Photocatalyst for Hydrogen Evolution.

CdS nanowires decorated with ultrathin MoS2 nanosheets were synthesized for the first time by ultrasonic exfoliation by using dimethylformamide as the dispersing agent. An excellent hydrogen evolution rate of 1914 μmol h(-1) (20 mg catalyst) under visible-light irradiation (λ ≥ 400 nm, ≈ 154 mW cm(-1) ) and an apparent quantum yield of 46.9% at λ=420 nm were achieved over the MoS2 /CdS composite. The presence of ultrathin MoS2 nanosheets (rich in active edge sites) on the CdS surface promotes the separation of photogenerated charge carriers and facilitates the surface processes of photocatalytic hydrogen evolution.

Synthesis and enhanced gas sensing properties of Au-nanoparticle decorated CdS nanowires

CdS nanowires (NWs) with an average diameter of 30 nm were synthesized by a solvothermal method and then Au nanoparticles with a size of 10–25 nm were decorated on the surface of the as-synthesized CdS NWs through a simple deposition process.

Cationic-exchange approach for conversion of two dimensional CdS to two dimensional Ag2S nanowires with an intermediate core–shell nanostructure towards supercapacitor application

A simple and facile chemical route for CdS, CdS/Ag2S and Ag2S nanowire surface architecture towards electrochemical supercapacitor application.

High-performance ultraviolet photodetectors based on CdS/CdS:SnS2 superlattice nanowires.

CdS heterostructure nanomaterials are attractive for their potential applications in integrated optoelectronic devices. Herein, the high-quality CdS/CdS:SnS2 superlattice nanowires were synthesized through a micro-environmental controlled co-evaporation technique, which shows periodic emission properties and that their structures are periodic and alternating. For the first time, we demonstrate the fabrication of high-performance ultraviolet photodetectors using unique CdS/CdS:SnS2 superlattice nanowires. The optoelectronic properties of the photodetectors were studied and compared to those devices based on pure CdS nanowires. The as-fabricated photodetectors (under 365 nm) based on CdS/CdS:SnS2 superlattice nanowires showed a high photocurrent to dark current ratio of 10(5), a large photoresponsivity of 2.5 × 10(3) A W(-1), a fast response time of 10 ms and an excellent external quantum efficiency of 8.6 × 10(5) at room temperature, which shows better performance than pure CdS nanowires photodetectors. The results indicate that CdS/CdS:SnS2 superlattice nanowires are very promising potential candidates in nanoscale electronic and optoelectronic devices.

Fabrication of CdS nanowires on TiO2 nanorods for solar cell application

A composition of CdS nanoparticles and nanowires were deposited on TiO2 nanorods by successive ionic layer adsorption and reaction method grown on Ti substrate. CdS/TiO2/Ti device were used as photoanode in solar cell. Efficiency, short circuit current, and open circuit voltage were measured. Also, electron life time in each Fermi level and order of recombination were obtained by open circuit voltage decay and short circuit photocurrent interrupt voltage; respectively. Our results showed that there is an optimum composition of CdS nanoparticles and nanowires which improves solar cell properties of this type of cell.

Strain Driven Spectral Broadening of Pb Ion Exchanged CdS Nanowires.

Broad visible photodetectors based on individual Pb ion exchanged CdS nanowires are reported. They are prepared via an ion exchange reaction initiated on the surface of CdS nanowires with a further diffusion of ionic reactants. The broadening of the response spectrum is relative to electronic band structure transition caused by the tensile strain in the lattice.

Growth of Hierarchical CdS Nanostructures on Fluorine-Doped Tin Oxide Glass Substrate

Hierarchical CdS nanostructures were grown on fluorine-doped tin oxide glass via a physical vapor transport method. Tin from the substrate catalyzed the growth of a flower-like hierarchical structure that consisted of a stem and branches at a growth temperature of 280 °C. The stem nanowires grew along ⟨001⟩ with a rare zinc blende structure while branched nanowires grew along ⟨0001⟩ with a wurtzite structure. A modified vapor–solid–solid mechanism dominated by the diffusion of source species along the surface of the quasi-liquid shell of the catalyst while keeping its crystalline solid core was proposed based on the finding of a faceted core–shell Sn catalyst. The tetragonal β-phase Sn structure was observed and may induce the epitaxial growth of zinc blende CdS nanowires through a thin quasi-liquid interface owing to the close lattice match to zinc blende CdS. In contrast, branches were grown via a vapor–liquid–solid mechanism by Sn catalysts, which were vapor-transported from the higher temperature zone...

High‐Performance Fiber‐Shaped All‐Solid‐State Asymmetric Supercapacitors Based on Ultrathin MnO2 Nanosheet/Carbon Fiber Cathodes for Wearable Electronics

Flexible fiber‐shaped supercapacitors have shown great potential in portable and wearable electronics. However, small specific capacitance and low operating voltage limit the practical application of fiber‐shaped supercapacitors in high energy density devices. Herein, direct growth of ultrathin MnO2 nanosheet arrays on conductive carbon fibers with robust adhesion is exhibited, which exhibit a high specific capacitance of 634.5 F g−1 at a current density of 2.5 A g−1 and possess superior cycle stability. When MnO2 nanosheet arrays on carbon fibers and graphene on carbon fibers are used as a positive electrode and a negative electrode, respectively, in an all‐solid‐state asymmetric supercapacitor (ASC), the ASC displays a high specific capacitance of 87.1 F g−1 and an exceptional energy density of 27.2 Wh kg−1. In addition, its capacitance retention reaches 95.2% over 3000 cycles, representing the excellent cyclic ability. The flexibility and mechanical stability of these ASCs are highlighted by the negligible degradation of their electrochemical performance even under severely bending states. Impressively, as‐prepared fiber‐shaped ASCs could successfully power a photodetector based on CdS nanowires without applying any external bias voltage. The excellent performance of all‐solid‐state ASCs opens up new opportunity for development of wearable and self‐powered nanodevices in near future.

Controllable synthesis of CdS nanowire by a facile solvothermal method and its temperature dependent photoluminescent property

CdS nanowires with controllable size, orientation, and morphology were synthesized on a large scale by a solvothermal method. The mechanism for the formation of CdS nanowires evolved from CdS spherical particles can be divided into a short-period solid–solid transformation process and a long-period ripening process. Near-band-emission without distinct split phenomenon was observed in the PL spectrum of CdS nanowires at 10 K. The best fit results based on Varshni empirical equation support our assignment of FX. Temperature dependent integrated peak intensity and linewidth of FX were analyzed by means of a two-step quenching process model and well fitted by Toyozawa's theory. All fitted results including thermal activation energy, LO-phonon energy were close to that observed in bulk CdS, indicating high quality of nanomaterial but also revealing its promising applications in photonics.

Simple synthesis of high-quality CdS nanowires using Au nanoparticles as catalyst

CdS nanowires were synthesized using a simple synthesis process using Au nanoparticles (average diameter: 13 nm) as catalyst. The growth conditions were optimized by varying the substrate temperature and the growth time of a thermal chemical-vapor-deposition system. CdS nanowires were successfully grown at temperatures above 480 °C. In fact, high-quality nanowires, with hexagonal wurtzite structures and an average diameter of 25 nm and length of 1.46 μm, were obtained after a 30-min synthesis at a growth temperature of 520 °C. Electron microscope images revealed that our CdS nanowires, grown at relatively lower growth temperatures, have higher average-aspect-ratio and smaller average-diameter than those previously reported in the literature. Our synthesis method resulted in CdS nanowires only without producing nanorods and nanobelts, which make it unnecessary to filter and purify nanowires from the mixture of nanowires, nanorods, and nanobelts.

Embedded nanowire window layers for enhanced quantum efficiency in window-absorber type solar cells like CdS/CdTe

Embedded CdS nanowires are used for improving the spectral transmission of the CdS window layer, thus enhancing the quantum efficiency of CdS–CdTe solar cells. Substantially higher light transmission is observed in the 300nm–550nm wavelength range. A nearly ideal spectral response of quantum efficiency over a wide spectral range provides evidence for improved light transmission through the window layer and enhanced absorption and carrier generation in the CdTe absorber layer. Nanowire CdS/CdTe solar cells on SnO2/ITO-soda lime glass substrates, and with Cu/graphite paste/silver paste as back contact electrodes, yield a power conversion efficiency of 12%. MoO3−x /Au back contacts were also investigated. With these back contacts, the nanowire CdS–CdTe solar cells exhibit efficiency comparable to the efficiency of their planar CdS counterparts. Junction transport mechanisms are delineated for advancing the basic understanding of device physics at the interface. Our results prove the efficacy of this nanowire approach for enhancing the quantum efficiency in window-absorber type solar cells (CdS–CdTe, CdS–CIGS and CdS–CZTSSe etc.) and other optoelectronic devices.

Hierarchical CdS Nanowires Based Rigid and Flexible Photodetectors with Ultrahigh Sensitivity.

Hierarchical CdS nanowires were synthesized via a facile vapor transport method, which were used to fabricate both rigid and flexible visible-light photodetectors. Studies found that the rigid photodetectors on SiO2/Si substrate showed ultrahigh photo-dark current ratio up to 1.96 × 10(4), several orders of magnitude higher than previously reported CdS nanostructures, as well as high specific detectivity (4.27 × 10(12) Jones), fast response speed and excellent environmental stability. Highly flexible photodetectors were also fabricated on polyimide substrate, which exhibited comparable photoresponse performance as the rigid one. In addition, the as-prepared flexible devices displayed excellent mechanical flexibility, electrical stability and folding endurance. The results indicate that the hierarchical CdS nanowires may be good candidates for nanoscale optoelectronic devices such as high-efficiency photoswitches and highly photosensitive detectors.

High-Performance Fully Nanostructured Photodetector with Single-Crystalline CdS Nanotubes as Active Layer and Very Long Ag Nanowires as Transparent Electrodes.

Long and single-crystalline CdS nanotubes (NTs) have been prepared via a physical evaporation process. A metal-semiconductor-metal full-nanostructured photodetector with CdS NTs as active layer and Ag nanowires (NWs) of low resistivity and high transmissivity as electrodes has been fabricated and characterized. The CdS NTs-based photodetectors exhibit high performance, such as lowest dark currents (0.19 nA) and high photoresponse ratio (Ilight/Idark ≈ 4016) (among CdS nanostructure network photodetectors and NTs netwok photodetectors reported so far) and very low operation voltages (0.5 V). The photoconduction mechanism, including the formation of a Schottky barrier at the interface of Ag NW and CdS NTs and the effect of oxygen adsorption process on the Schottky barrier has also been provided in detail based on the studies of CdS NTs photodetector in air and vacuum. Furthermore, CdS NTs photodetector exhibits an enhanced photosensitivity as compared with CdS NWs photodetector. The enhancement in performance is dependent on the larger surface area of NTs adsorbing more oxygen in air and the microcavity structure of NTs with higher light absorption efficiency and external quantum efficiency. It is believed that CdS NTs can potentially be useful in the designs of 1D CdS-based optoelectronic devices and solar cells.

Effects of the CdS nanowire layer on the photocurrent generation in CIGS solar cells

In this paper, we perform a simulation on nanowire-CdS/bulk-CIGS heterojunction solar cells. In order to calculate the improvement in the efficiency, the light generated current density for the junction was calculated and it is shown that replacing CdS nanowires (NWs) with bulk CdS, leads up to 17% improving in short circuit current. Band diagram of typical bulk and NW-CdS/CIGS has been calculated and an improvement in band discontinuity in NW-CdS/CIGS observed. Also, light generated current density calculation shows absorption edge shift in CdS NWs, especially in the range of 400–480nm, in comparison bulk CdS.

Gas Sensors Based on Metal Sulfide Zn(1-x)Cd(x)S Nanowires with Excellent Performance.

Metal sulfide Zn1-xCdxS nanowires (NWs) covering the entire compositional range prepared by one step solvothermal method were used to fabricate gas sensors. This is the first time for ternary metal sulfide nanostructures to be used in the field of gas sensing. Surprisingly, the sensors based on Zn1-xCdxS nanowires were found to exhibit enhanced response to ethanol compared to those of binary CdS and ZnS NWs. Especially for the sensor based on the Zn1-xCdxS (x = 0.4) NWs, a large sensor response (s = 12.8) and a quick rise time (2 s) and recovery time (1 s) were observed at 206 °C toward 20 ppm ethanol, showing preferred selectivity. A dynamic equilibrium mechanism of oxygen molecules absorption process and carrier intensity change in the NWs was used to explain the higher response of Zn1-xCdxS. The reason for the much quicker response and recovery speed of the Zn1-xCdxS NWs than those of the binary ZnS NWs was also discussed. These results demonstrated that the growth of metal sulfide Zn1-xCdxS nanostructures can be utilized to develop gas sensors with high performance.