Spectral properties and microstructure of sputtered WOx films for solar conversion applications

Tungsten oxides (WO_x) films have gained promising attention in terms of selective solar absorption due to its high intrinsic absorption properties. We fabricated a series of single-layer WO_x films on aluminum substrates by a magnetron sputtering system. The optical absorption properties of the film were investigated by spectrophotometer and ellipsometry. We found that the optical properties of the film were very sensitive to the change of the thickness. The result showed the highest α value can reach up 0.82 with the thickness of 26 nm at 0.6 Pa or 70 nm at 1.5 Pa, and both ε values was around 0.05, indicating the high spectral selectivity properties. The different reflectance evolutions presented a wide range of color appearances, such as yellow, reddish, cyan, and blue. Moreover, the surface morphologies and phase structures of single-layer WO_x films were investigated by SEM, XRD, and Raman. A WO_x/SiO₂ solar selective absorber coating indicated that the as-obtained WO_x film was a promising application in solar-thermal conversion.     

Nanostructured ultraviolet resistant polymer coatings

Nanoparticle-embedded acrylic coatings that can absorb copious amounts of UV radiation yet scatter little were developed to protect base fabrics from sun-induced degradation. Zinc oxide and titanium dioxide nanoparticles with diameters ranging from 15 to 70 nm were used. Nanoparticles (5 wt%) were dispersed in acrylic emulsions. Nanoparticle-embedded acrylic films of 10 μm and 20 μm thick were prepared and bonded to Kevlar fabric. Mechanical tests as well as infrared, visible and UV spectroscopy were used to characterize nanoparticle-embedded acrylic emulsions and coated Kevlar fabric.The changes in mechanical and chemical properties of Kevlar fabric after a day and week of intense UV exposure were assessed using tear and strip tensile testing, UV, visible and infrared spectroscopy, and wide and small angle X-ray analysis. Tear and tensile data, with support from UV results, showed that 20 μm nanoparticle-embedded coatings largely prevented degradation of Kevlar fabric, allowing only 5% of the degradation that occurred in the unprotected fabric after a week of UV exposure.     

Nanostructured ZrO2-Coated TiO2 Electrodes for Dye-Sensitised Solar Cells

Thin films of ZrO₂ were deposited on nanostructured anatase TiO₂ electrodes via sol-gel route and utilised in the assembly of a dye-sensitised solar cells (DSSCs) forming nanostructured core-shell networks. The ZrO₂-coated TiO₂ electrodes were characterised by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and constructing a DSSC. The characterisation concluded that core-shell morphologies were produced with varying ZrO₂ shell thickness without altering the anatase TiO₂ core. When a DSSC was constructed from the ZrO₂:TiO₂ core-shell electrode, the efficiency increased to 2.27% from 0.42% for the uncoated TiO₂ electrode. As the ZrO₂ shell thickness increased, the cell efficiency was reduced.     

Effect of carbon black content on electrical and microwave absorbing properties of polyaniline/carbon black nanocomposites

Carbon black coated with polyaniline, forming a core-shell structure, was synthesized by in situ polymerization at different carbon black contents (5-30 wt.%) and introduced into epoxy resin to be a microwave absorber. The spectroscopic characterizations of the formation processes of polyaniline/carbon black composites were studied using Fourier transform infrared, ultraviolet-visible spectrophotometer, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and electron spin resonance. Microwave absorbing properties were investigated by measuring reflection loss in the 2-18 and 18-40 GHz microwave frequencies range using the free space method. The results showed that a wider absorption frequency range could be obtained by adding different carbon black contents in polyaniline.     

An alternative efficient redox couple for the dye-sensitized solar cell system

A series of new cobalt complexes [Co(LLL)(2)X(2)] were synthesized and evaluated as redox mediators for dye-sensitized nanocrystalline TiO(2) solar cells. The structure of the ligand and the nature of the counterions were found to influence the photovoltaic performance. The one-electron-transfer redox mediator [Co(dbbip)(2)](ClO(4))(2) (dbbip = 2,6-bis(1'-butylbenzimidazol-2'-yl)pyridine) performed best among the compounds investigated. Photovoltaic cells incorporating this redox mediator yielded incident photon-to-current conversion efficiencies (IPCE) of up to 80%. The overall yield of light-to-electric power conversion reached 8 % under simulated AM1.5 sunlight at 100 W m(-2) intensity and more than 4% at 1000 W m(-2). Photoelectrodes coated with a 2 microm thick nanoporous layer and a 4 microm thick light-scattering layer, sensitized with a hydrophobic ruthenium dye, gave the best results.     

Eco‐friendly conductive polymer nanocomposites (CPC) for solar absorbers design

To reduce both the cost and the environmental impact of copper‐based thermal solar absorbers, we have investigated their possible substitution by bio‐based conductive polymer nanocomposite (CPC) elements. Our results show that carbon nanotubes (CNT) have no significant influence on polymers’ calorimetric properties such as T_m and T_g but lead to a strong increase in crystallinity of poly(lactic acid) (PLA) and to a lesser extent of poly(amide 12) poly(amide 12) (PA12) for 2 and 3 CNT wt % respectively. Percolation thresholds as low as 0.5 and 0.58 were obtained for PA12 and PLA, respectively, and visco‐elastic properties such as η*, G’ and G” were found to increase exponentially with CNT content confirming the formation of a CNT network within the matrix. All CPC are absorbing more energy in the visible and infrared than in the ultraviolet wavelength ranges. Finally, the thermal conductivity k of PLA–CNT and PA12–CNT were increased, respectively, of 85% and 24%, to reach 0.28 W.m^?1.K^?1 and 0.26 W.m^?1.K^?1, for only 5 wt% CNT. The figure of merit suggests that PA12 is the polymer which satisfies at best all criteria, particularly combining a lower viscosity at almost equivalent thermal conductivity and absorptivity. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and characterization of benzobisthiazole based polymers as donor materials for organic solar cells

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Thermal decomposition and cobalt species transformation of carbon nanotubes supported cobalt catalyst for Fischer-Tropsch synthesis

The effect of calcination condition on the cobalt species and Fischer-Tropsch synthesis (FTS) was studied. It was found that higher calcination temperature resulted in decreased FTS activities because CNTs were consumed by oxidation in air at temperature higher than 230°C. Cobalt species went through transformation from Co3O4 to metallic Co in Ar by autoreduction at temperature over 500°C. The autoreduction route might be Co3O4→CoO→Co or Co3O4→Co2C→Co. Reduction at temperature higher than 500°C also resulted in decreased FTS activities due to the methanation of CNTs in hydrogen.     

Comparative study of dye-sensitized solar cell utilizing selenium and palladium cathode

This work is concerned with the comparative study of dye-sensitized solar cell (DSSC) utilizing selenium (Se) and palladium (Pd) cathode. The influence of concentration of selenium dioxide (SeO₂) and palladium chloride (PdCl₂) on the performance of the device has been investigated. The Se and Pd cathode have been prepared via dip coating-based multilayer deposition technique. The device using Se cathode with seven layers possesses the highest performance in term of short-circuit current density (J_sc). The photovoltaic measurement results show that the device utilizing Pd cathode demonstrates higher power conversion efficiency (η) compared with that of the device using Se cathode. The highest η of the device with Se and Pd cathode are 0.071 and 0.169%, obtained at the 0.5 ?M SeO₂ and 0.60 ?M PdCl₂, respectively. The Pd cathode-based device prepared with 0.60 ?M PdCl₂ owns the highest η due to the lowest sheet resistance (R_s). These photovoltaic results imply single material has potential to be modified into binary or ternary cathode material in order to improve the performance of DSSC.     

Nanostructured carbon black filled polypropylene/polystyrene blends containing styrene-butadiene-styrene copolymer: Influence of morphology on electrical resistivity

This paper is part of a comprehensive study on using selective localization of carbon black (CB) at the interface of immiscible polymer blends in order to reduce the percolation threshold concentration and enhance the conductivity of the blends. CB was successfully localized at the interface of polypropylene/polystyrene (PP/PS) blend by introducing styrene-butadiene-styrene (SBS) tri-block copolymer to the blend. In CB-PP/PS/SBS blends, CB has higher affinity for the polybutadiene (PBD) section of the SBS copolymer, whereas in CB-PP/PS blends, CB prefers the PS phase. PP/PS interface is one of the preferred locations for the SBS copolymer in the (PP/PS) blend; at which the PBD section of the SBS copolymer forms a few nanometers thick layer able to accommodate the CB nano-particles. The influence of SBS addition on the morphology and electrical properties of various PP/PS blends filled with 1 vol% CB were studied. SBS influence on the conductivity of PP/PS blends was found to be a function of the PP/PS volume ratio and SBS loading. The most dramatic increase in conductivity was found in the (60/40) and (70/30) PP/PS blends upon the addition of 5 vol% SBS. 5 vol% SBS was found to be the optimum loading for most blends. Using 10 vol% of SBS was reported to deteriorate electrical conductivity of the conductive co-continuous PP/PS blends. For all blends studied, SBS addition was found to compatibilize the blends. Finer morphologies were obtained by increasing SBS loading.     

Polymeric materials for solar water purification

Solar-based desalination or water purification is regarded as one of the promising solutions to global water scarcity as the only energy input is abundant and sustainable solar light. Interfacial solar vapor generation (SVG), which converts natural sunlight into clean water vapor, has attracted extensive research interests due to its high-energy utilization efficiency and simple implementation. With tunable molecular structures and tailorable physical properties, polymers have demonstrated great potential as candidate materials for solar evaporators. In this review, we summarize the recent progress on polymer materials for solar-powered water purification. First, we present functional polymers with highly tunable molecular composition and morphology as high-efficiency solar absorbers. Next, the recent development of various polymeric materials and structural engineering strategies for adequate water supply and efficient thermal management are discussed, along with their excellent desalination and purification performance. Last, we outline the challenges and future directions on the further development of polymer materials for solar water purification technologies.     

Waxes for powder coatings

Since the first beginnings at the end of the 50^th, the powder coating technology has become a perfected alternative in product and procedure respect to liquid paints. Powder coatings are primarily a mixture of synthetic resins, pigments and additives offering economical and ecological advantages compared to other coating systems. The raw materials are mixed, extruded and ground to coating powders. Waxes play an important part as additives in powder coatings. Production, storage and processing as well as the properties of the applied powder coating can be influenced positively by different waxes. Various waxes and their advantages are demonstrated by practical advantages.     

Nickel/cobalt based materials for supercapacitors

We briefly summarize the fundamental mechanism of supercapacitors and classify them into three kinds according to the different energy storage mechanism. We further discuss the energy storage mechanism of nickel/cobalt based materials, and we suggest that these kinds of battery-type materials should be classified into hybrid supercapacitor instead of pseudocapacitors.     

Development of niobium-promoted cobalt catalysts on carbon nanotubes for Fischer-Tropsch synthesis

Cobalt-based catalysts were prepared by a wet impregnation method on carbon nanotubes (CNTs) support and promoted with niobium.Samples were characterized by nitrogen adsorption,TEM,XRD,TPR,TPO and H2-TPD.Addition of niobium increased the dispersion of cobalt but decreased the catalysts reducibility.Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K,1 atm and H2/CO=2 for 5 h.Addition of niobium enhanced the C5+ hydrocarbons selectivity by 39% and reduced methane selectivity by 59%.These effects were more pronounced for 0.04%Nb/Co/CNTs catalyst,compared with those observed for other niobium compositions.     

Synthesis, characterization and activity of alumina-supported cobalt nitride for NO decomposition

A new type of transition metal nitride, viz. alumina-supported cobalt nitride, was synthesized for the first time by NH₃-temperature-programmed reaction, and its structure was characterized by BET, X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS) techniques. The supported cobalt nitride performs much better than its bulk counterpart for NO decomposition, owing to its small crystal size, high thermal stability and big surface area.     

Process optimization of dip-coated MWCNTs thin-films: Counter electrode in dye sensitized solar cells

Present research article emphasizes the first report on a simple and cost-effective ‘dip and dry’ coating method to coat MWCNTs at room temperature as a counter electrode towards dye sensitized solar cells (DSSCs) with ZnO/Eosin-Y as a photoanode. Process optimization through the number of dips (10, 15, 18, and 20) have been performed and compared to standard platinum (Pt) as counter electrode with iodide-triiodide as a liquid electrolyte. Photovoltaic performance through current density-voltage characteristic under standard 1 Sun illumination condition (AM 1.5G, 100 ​mW/cm²) and external quantum efficiency have been well supported which are correlated through structural, surface morphological, and electrochemical studies. Interestingly, DSSCs device with 18 cycles of MWCNTs yields half of the power conversion efficiency than that of Pt device.     

Donor-acceptor conjugated cooligomers for single molecule solar cells

Five novel donor-acceptor(D-A) conjugated cooligomers(F4B-hP,F5B-hP,F5B2[1,2]-hP,F5B2[1,3]-hP and F7B2[1,2]-hP) were synthesized.The absorption spectra of the cooligomers cover a wide range from 300 nm to 630 nm.The cooligomers could form films featured by alternating D-A lamellar nanostructures with the periods relative to the molecular lengths after thermal annealing or solvent vapor annealing.Single molecule solar cells were fabricated,and F5B-hP exhibited the best device performance.When the film of F5B-hP was thermally annealed,a power conversion efficiency(PCE) of 1.56% was realized.With solvent vapor annealing,the PCE could be further improved to 1.72% with a short-circuit current(J SC) of 5.76 mA/cm 2,an open-circuit voltage(V OC) of 0.87 V and a fill factor(FF) of 0.34.