Showing papers in "Solar Energy Materials in 1990"
TL;DR: In this article, the limits of solar radiation concentration in geometrical and fluorescent systems are described as a function of the index of refraction, angular collection range, as well as the frequency shift.
Abstract: Much work has been done over the past 10 years on the concentration of solar radiation using a variety of devices. To concentrate the light, photons from a larger area are collected and directed to a smaller area. Some devices use geometrical optics, or a change in index of refraction to increase the illumination on a surface above the incident solar level. Other systems use a frequency or Stokes shift to increase the illumination of light at one photon energy at the expense of another. There is often confusion as to the concentration limit imposed by basic physical laws on these different types of systems. Presented is a unification of the ideas and principles developed for the various classifications of concentrators. Equations are developed that describe the limits of concentration in geometrical and fluorescent systems. Concentration is shown to be a function of the index of refraction, angular collection range, as well as the frequency shift. Applications of the ideas involve the understanding of diffuse radiation concentrators and the solar powered laser.
229 citations
TL;DR: In this paper, photoactive iron pyrite (FeS2) thin film layers have been synthesized by a simple method involving the reaction of Fe3O4 or Fe2O3 with elemental sulfur.
Abstract: Photoactive iron pyrite (FeS2) thin film layers have been synthesized by a simple method involving the reaction of Fe3O4 or Fe2O3 with elemental sulfur. The films were formed on a variety of different substrate materials by converting or sulfurizing iron oxide layers. The subsequent sulfur treatment of the oxide layers consisted of exposure of the films to gaseous sulfur in open or closed ampules at 350°C for 0.5–2 h. The morphology, composition and photoactivity of the films produced were checked using X-ray diffraction, X-ray photoelectron spectroscopy (ESCA), optical absorption, steady state and transient photoconductivity. The best films showed good crystallinity and purity with concurrent photoconductivity and photoelectrochemical response. The ability of this technique to produce photoactive material can be explained by interpretation of the Gibbs ternary phase diagram for the FeOS system, and may be related to the production of photoactive pyrite in nature. A discussion is made as to the future improvement of the solar cell response by proper optimization of geometric and configurational properties.
137 citations
TL;DR: In this article, the chemical stability of low-melting, ternary molten salt mixtures of NaNO 3, KNO 3 and either Ca(NO 3 ) 2 or LiNO 3 was investigated.
Abstract: Molten salts that melt at low temperature and are stable at high temperature would be very useful for solar thermal energy applications. We have investigated the chemical stability of low-melting, ternary molten salt mixtures of NaNO 3 , KNO 3 and either Ca(NO 3 ) 2 or LiNO 3 and determined the types of decomposition products formed under equilibrium conditions. The initial decomposition reaction, nitrate ⇆ nitrite + oxygen, proceeds to approximately the same extent in ternary mixtures as in an equimolar binary mixture of NaNO 3 and KNO 3 . Decomposition at high temperature was due to reactions of nitrite and nitrate that yield oxide ions. The latter reactions were strongly dependent on the composition of ternary mixtures and it was found that mixtures containing lithium nitrate were more stable than those containing calcium nitrate. Although ternary mixtures are less stable than the binary mixture, they appear to be useable at relatively high temperatures.
122 citations
65 citations
TL;DR: In this paper, chemical deposition of lead sulfide thin films on glass substrates was used to satisfy the basic requirements for solar control coatings for window glazing applications in warm climates, where a low transmittance ( ∼10% to 30% ) in the visible region is coupled with an appreciable reflectance for infrared radiation.
Abstract: Chemically deposited lead sulfide thin films on glass substrates are found to satisfy the basic requirements for solar control coatings for window glazing applications in warm climates, where a low transmittance ( ∼10%–30% ) in the visible region is to be coupled with an appreciable reflectance for infrared radiation The depositions were made on glass substrates from alkaline/ ammoniacal baths of lead acetate, thiourea and small amounts of triethanolamine The coating can produce a gray, purple or bluish appearance in reflected daylight with near normal specular reflectance (visible region) of ∼15%–25% These coatings appear yellowish in transmitted daylight with 7%–25% transmittance, depending on the duration of deposition The integrated infrared (070 to 25 μm) reflectance for air mass (AM) 2 solar spectrum of typical PbS coated glass is ∼37% as compared to ∼7% for the uncoated glass The advantages of chemical deposition for large area coatings, the desirable features of PbS as a solar control coating, and toxicity considerations are discussed
65 citations
TL;DR: In this paper, a copper-indium alloys were prepared by electroplating from citric acid bath onto a Ti substrate, and the as-deposited layers were heated in H2S. X-ray diffraction showed the annealed layers to be CuInS2 with the chalcopyrite structure, where the CuIn5S8 phase was included during annealing process.
Abstract: Copper-indium alloys were prepared by electroplating from citric acid (C6H8O7·H2O) baths onto Ti substrate. Formation of the alloys was carried out by direct codeposition of the elements and by sequential electrodeposition of copper and indium. Studies of the alloy formation by electrochemical measurements and X-ray diffraction were performed. The presence of Cu7In4 in direct deposit as well as in sequentially electrodeposited material was observed during the alloy formation. The as-deposited layers were heated in H2S. X-ray diffraction showed the annealed layers to be CuInS2 with the chalcopyrite structure, where the CuIn5S8 phase was included during the annealing process. Photoelectrochemical characterization of the samples allowed us to determine the photoconductivity which is related with the Cu/In ratio in the samples. The energy gap for CuInS2 photoelectrodes in polysulphide solution was 1.57 eV.
55 citations
TL;DR: In this article, the optical properties of titanium-nitride-based multilayers are reported, including the transmittance and reflectance spectra as well as the solar optical parameters of the triple layers.
Abstract: Results on the optical properties of titanium-nitride-based multilayers are reported. Single layer TiO2 and TiO2/TiN/TiO2 triple layers were prepared by DC magnetron sputtering. The refractive index n and the extinction coefficient k have been calculated for the TiO2. The transmittance and reflectance spectra as well as the solar optical parameters of the triple layers are presented. The plasma current used to sputter the TiN is noted to affect the performance of the triple layer. The triple layer is shown to be an option as a solar control coating.
53 citations
TL;DR: In this article, two types of texture have been proposed to achieve light trapping in crystalline solar cells: top and/or back surface textures of realisable, "regular" facets belonging to a small class of orientations, with specific layout, to minimise escape patterns and so enhance overall beam path length in the cell.
Abstract: The light trapping properties of textured optical sheets have attracted interest lately because of their potential in reducing the thickness of solar cell material. This provides a way to lower unit costs as well as reduce bulk recombination, thus raising open-circuit voltage. The strategy can be applied to any non-imaging system with limited absorbance. Two types of texture have been proposed to achieve light trapping in crystalline solar cells. One idealised system generates a random (Lambertian) distribution of light in the cell either by refraction from a diffuse top surface or reflection from a diffuse back surface texture. The other comprises top and / or back surface textures of realisable, “regular” facets belonging to a small class of orientations, with specific layout, to minimise escape patterns and so enhance overall beam pathlength in the cell. The latter facet class may be periodic or randomly sized. Concentrating solar cells that receive light over a limited range of angles of incidence provide an environment for further refining a light trapping technique. When the top surface of a crystalline silicon randomising cell is “tuned” to accept only this incident cone, its Auger-limited efficiency is almost independent of concentration. Studies have shown that some regular textures formed on crystalline silicon by an anisotropic etch yield a higher absorbance than a diffuse texture, over a limited range of angles of incidence. The most promising class of these uses a pre-etch crystallographic orientation other than the usual 〈100〉 to asymmetric structures from intersecting 〈111〉 planes. These require only a top surface texture, which simplifies back surface fabrication and demands less from the quality of its reflector than a doubly textured design. They also nearly eliminate top surface reflection over the full solar spectrum without depending on an antireflection coating.
53 citations
TL;DR: In this article, a two-stage concentrator with a rectangular glass heliostat and a parabolic dish was used to produce a primary image of the sun at a distance of 100 m to the South.
Abstract: The combination of a stationary parabolic dish concentrator and a heliostat has come to be known as solar furnace. The advantage of this combination as compared to a parabolic dish directly tracking the sun is that the focus is stationary. Both dish and instrumentation of the focus can be placed indoors. In the usual configuration a heliostat is facing a dish of approximately equal area. We have combined a rectangular glass heliostat of area 52 m2 and focal length 100 m with a parabolic dish of area 5.7 m2 and focal length 1.93 m to a two-stage concentrator. In this arrangement the heliostat produces a primary image of the sun at a distance of 100 m to the South. This image has a diameter of roughly 1 m. The bundle of rays contributing to this image has a cross section equal to the area of the dish at a distance of 70 m south of the heliostat. At this location we placed the dish in order to intercept all rays. From the primary image of the sun situated 30 m behind, the dish produces a secondary image in a plane situated 12 cm behind its focal plane. The secondary image is calculated to have a diameter of 6 cm and a numerical aperture of 0.64 ( f- number = 0.78 ). Thus except for reflectivity losses, the concentration ratio of the furnace is expected to correspond to that of the dish if used alone tracking the sun, while the total power is basically that intercepted by the much larger heliostat. This two-stage concentration has the advantage of requiring a smaller dish which can be at the same time cheaper and of higher optical quality. The disadvantage is that oblique reflection at the heliostat causes an astigmatism which distorts the secondary image to an ellipse roughly 15 cm × 6 cm and reduces the concentration ratio accordingly. This effect is larger for larger angles of incidence and for smaller dish dimensions. We show the flux distribution measured in the secondary plane of our heliostat and discuss possibilities to improve the optics by compensating the astigmatism.
50 citations
TL;DR: In this paper, fluorescent dyes were incorporated into polyethylene sheets made by extrusion to convert light from the green part of the spectrum into red light, which increased the yield of tomato and rose bushes.
Abstract: New greenhouse plastic covers were prepared by incorporation of fluorescent dyes into polyethylene sheets made by extrusion. These dyes convert light from the green part of the spectrum into red light. The use of these sheets as greenhouse covers increased the weight of the tomato fruit yields by 19.6% and the number of flowering branches on rose bushes by 26.7% as compared to sheets without the dye. The increased yield was primarily due to a morphogenetic response of the plants to the spectral change of the light, which enhanced the development of the desired organs. In addition, it is possible that there was an increased rate of photosynthesis.
43 citations
TL;DR: In this article, two different approaches for designing a linear Fresnel reflector solar concentrator (LFRSC) for a triangular absorber configuration are presented, one allowing a variation in the width of the mirror elements, while the second uses mirror elements of equal width.
Abstract: Two different approaches for designing a linear Fresnel reflector solar concentrator (LFRSC) for a triangular absorber configuration are presented. The first approach allows a variation in the width of the mirror elements, while the second uses mirror elements of equal width. For each design, the distribution of local concentration ratio (LCR) on the surfaces of two sides of the absorber which intercept the solar radiation reflected from concentrator has been investigated using the ray trace technique. Results are plotted graphically and discussed.
TL;DR: In this article, non-stoichiometric SnO x thin films were made by RF magnetron sputtering of Sn in Ar+O2 onto unheated glass.
Abstract: Non-stoichiometric SnO x thin films were made by RF magnetron sputtering of Sn in Ar+O2 onto unheated glass. Electrical DC resistivity (ϱ) as well as spectral transmittance and reflectance were studied as a function of sputtering parameters. A sharp minimum in ϱ was observed at a well-defined gas composition. Optimized parameters gave films with ϱ≈3sx10 −3 Ω cm at low deposition rate ( r ), and ϱ≈10 −2 Ω cm at r ≈ 3 nm/s . The luminous transmittance was ∼ 75%.
TL;DR: In this paper, a photoelectrochemical study of the behavior of p-type thin films of CuInSe2 (CIS) in acqueous acidic solutions is presented showing that the liquid junction can be efficiently used for the characterization of as-grown layers.
Abstract: A photoelectrochemical study of the behaviour of p-type thin films of CuInSe2 (CIS) in acqueous acidic solutions is presented showing that the liquid junction can be efficiently used for the characterization of as-grown layers. Standard films have doping levels in the range of 1016 cm−3 and their spectral responses present high quantum efficiencies (∼ 0.9). The films have a poor photoresponse in electrolyte without added redox species, which has been attributed to slow interfacial kinetics for the reduction of protons. The deposition on the surface of metal islands that catalyze the hydrogen evolution (Pd, Pt) greatly enhances the photoresponse allowing the transfer towards the solution of the internal photocurrent via the hydrogen evolution. With the addition of Eu3+ ions in solution, the transfer of photocurrent is achieved on bare surfaces allowing the complete characterization of the layer without surface treatment. Changes of the band edge position (i.e. barrier height changes) with the illumination were observed. They are associated with losses of about 0.5 V on the predicted open circuit voltage. The similitude with the behaviour of solid state cells is underlined.
TL;DR: The pelt of polar bears acts as a translucent insulation through the hairs of which diffuse light is transferred by a combination of scattered light and luminescence light collection as mentioned in this paper, which may help the polar bear to determine the approximate position of the sun and thus to navigate under diffuse arctic visibility but also to locate ice-free sea surfaces with significantly reduced light scattering properties as compared with ice-covered surfaces.
Abstract: The pelt of polar bears acts as a translucent insulation through the hairs of which diffuse light is transferred by a combination of scattered light and luminescence light collection. The optical and morphological differences with respect to the white hair of other mammals have been investigated by scanning light microscope and UV-laser-induced luminescence studies and model experiments performed which support the suggested mechanism. An evaluation of physiological information on the energy turnover and dissipation in the polar bear suggests that comparatively little additional energy can be gained by harvesting solar radiation. However, due to the peculiar energy transparent pelt of the polar and the significant cooling of peripheral tissues suffered during cold ambient conditions, solar irradiation may change subcutaneous temperatures by as much as 10°C. It is suggested that the polar bear's skin, using the temperature pattern produced on its surface by scattered light, calibrated for wind chill against the body-temperature-controlled latissimus sheets, may be used as a kind of sensory system. This may help the polar bear to determine the approximate position of the sun and thus to navigate under diffuse arctic visibility but also to locate ice-free sea surfaces with significantly reduced light scattering properties as compared with ice-covered surfaces.
TL;DR: In this paper, the optical properties of the dye molecules in the layer and in the sol-gel solutions are studied as a function of dye concentration and changes in the thermal treatment of the layers.
Abstract: Inorganic glasses prepared by the “cold” chemical sol-gel process can present an alternative host material for organic fluorescent dyes. We report on measurements done on thin SiO2 layers prepared as sol-gels and doped with various dyes on a glass substrate. The preparation is done by dip-coating of the substrate in the corresponding alcoxide solutions. Good-quality layers without crazing after drying are achieved with a thickness of up to 1–2 μm. The measurements include absorption measurements (UV to IR), fluorescence and excitation measurements (visible to NIR), and measurements of photo-decomposition. The optical properties of the dye molecules in the layer and in the sol-gel solutions are studied as a function of dye concentration and changes in the thermal treatment of the layers. The results are examined for their applicability to fluorescent planar concentrators. Further we report on small silver islands (submicron size) brought into the sol-gel solution as stabilised colloids or by chemical reduction of Ag+ salts. According to theoretical predictions, the electromagnetic interaction between silver surface plasmons and dye molecules can result, under certain conditions, in an enhanced fluorescence quantum efficiency and photostability of the dye.
TL;DR: In this paper, Cadmium sulphide films have been deposited on nonconducting glass slides in an alkaline medium by a chemical bath deposition process and the effect of arsenic doping on them is briefly revealed.
Abstract: Cadmium sulphide films have been deposited on nonconducting glass slides in an alkaline medium by a chemical bath deposition process. The arsenic doping concentration was varied from 0.01 to 1 wt%. Film thickness is observed to vary with arsenic doping concentration. The films are characterised in terms of their electrical transport and optical properties. The effect of arsenic doping on them is briefly revealed.
TL;DR: In this article, a latent heat storage system of ternary carbonate eutectic mixture (32.1 wt% Li2CO3; 34.5wt% K2Co3; 33.4wt. Na2CO 3 ) was studied in a shell-tube heat exchanger.
Abstract: A latent heat storage system of ternary carbonate eutectic mixture (32.1 wt% Li2CO3; 34.5 wt% K2CO3; 33.4 wt% Na2CO3) has been studied in a shell-tube heat exchanger. In the heat storage stage, the phase change transition of the ternary eutectic takes place in the temperature range 395–400°C. In the heat recovery stage, the carbonate eutectic exhibits a distinct phase transition temperature (395–397°C) without supercooling over 50 thermal cycles. The average heat transfer coefficient ranges from 34 to 51 W/m2·K with heat transfer fluid's Reynolds number in the range 5 × 103−2.1 × 104. It has been found that 316-stainless steel is a suitable material without appreciable corrosion for the present ternary eutectic mixture.
TL;DR: In this paper, the authors show that with suitable optics to bring radiation onto bifacial solar cells, the power output per unit area of silicon wafer may in principle be double that of equivalent monofacial cells for the same incident radiation intensity level.
Abstract: With suitable optics to bring radiation onto bifacial solar cells the power output per unit area of silicon wafer may in principle be double that of equivalent monofacial cells for the same incident radiation intensity level. Bifacial cells in fixed non-imaging concentrators which incorporate a coupling dielectric may, in principle, achieve up to seven times the annual energy output of equal area monofacial cells in flat panels. In practice the power gains are closer to three due to optical and thermal losses and asymmetry between the faces of currently available bifacial cells.
TL;DR: In this paper, thin films of SnO2:F (a transmitting selective surface) and PbS (a selective absorber) are evaluated in a spray pyrolysis technique.
Abstract: Thin films of SnO2:F (a transmitting selective surface) and PbS (a selective absorber) are evaluated in this study. The coatings are prepared by a spray pyrolysis technique. SnO2:F is prepared on glass slides at a temperature of 400°C, with a thickness of 0.6 μm while PbS is prepared on aluminium substrates at a temperature of 250°C with a thickness of 0.9 μm. Properties of each surface are investigated separately. SnO2:F films showed 90% optical transmission at solar maximum (550 nm) and high infrared reflectivity indicating that the film is a good heat mirror with low sheet resistance of 3 ω/□. Chemically deposited PbS films on chemically etched aluminium substrate have high absorptance ( α = 0.92 ) in the visible spectrum and small thermal emittance ( ϵ (100° C ) = 0.12 ). This indicates the film is a good solar selective surface. Comparison studies of the stagnation temperature of different absorbing systems showed some improvement related to the transmission selective properties of the tin oxide film. Such an improvement can be more pronounced with high temperature collectors where radiative losses are greater.
TL;DR: In this paper, the authors extended an existing heat transfer model of multipane windows filled with gasses to include the effects of infrared absorption within the gasses, and presented a one-dimensional, finite-element, control-volume approach for calculating the heat transfer across a horizontal window filled with an infrared absorbing gas.
Abstract: This paper extends an existing heat transfer model of multipane windows filled with gasses to include the effects of infrared absorption within the gasses. A one-dimensional, finite-element, control-volume approach for calculating the heat transfer across a horizontal window filled with an infrared absorbing gas is presented. This model includes the coupled effects of conduction and radiation but not convection. Experimental data on the heat transfer rates through windows filled with infrared absorbing gasses and heated from above (to minimize convection) agree with results from this model. Infrared absorbing gasses are shown to have a small effect on reducing heat transfer through common window systems and are not as effective as low-emittance coatings for reducing radiative heat transfer.
TL;DR: In this paper, the influence of chemical and photoelectrochemical etching on the physical parameters (grain size, d, donor concentration, N D and hole diffusion length, L p ) determining the photoelectronchemical behaviour of electrodeposited CdSe 0.65 Te 0.35 thin films in contact with sulfide/polysulfide electrolyte has been systematically studied.
Abstract: The influence of chemical and photoelectrochemical etching on the physical parameters (grain size, d , donor concentration, N D and hole diffusion length, L p ) determining the photoelectrochemical behaviour of electrodeposited CdSe 0.65 Te 0.35 thin films in contact with sulfide/polysulfide electrolyte has been systematically studied. Photoetching in 1M Na 2 SO 3 of the electrodes, annealed at 600°C in Ar with several ppm of O 2 , produces maximum quantum efficiencies of near 100% with monochromatic radiation of 560 nm. As a result of this optimized study a PEC cell has been fabricated.
TL;DR: In this paper, a mechanistic model of Ag film degradation consisting of initiation, propagation, and termination steps is proposed, based on the results of their studies and other reported work.
Abstract: Humidity-induced degradation in typical Ag-based low-emissivity films appears to be caused primarily by physical agglomeration of Ag, not chemical reaction, and its resulting disruption of overlying layers. This physical restructuring is controlled fundamentally by changes in surface free energy and diffusion of Ag. Both temperature and humidity as well as the surrounding layers, the substrate, and particulate contamination affect the process. Based on the results of our studies and other reported work, a mechanistic model of Ag film degradation consisting of initiation, propagation, and termination steps is proposed.
TL;DR: In this paper, thin films of hydrated manganese oxide were electrodeposited out of a base solution onto conductive SnO2:F glass, showing the ability to reversibly store ions of dissociated water, however they show phase instability upon longer cycling.
Abstract: Thin films of hydrated manganese oxide were electrodeposited out of a base solution onto conductive SnO2: F glass. When cycled in a 1 M KOH solution, these films show the ability to reversibly store ions of dissociated water, however they show phase instability upon longer cycling. X-ray photoelectron spectroscopy was employed to investigate the chemical composition of the manganese oxide films. Our results indicate that hydrated MnO2 is the composition of the film in the oxidized state. Very low coloration was noted in these films making them useful for transparent counter-electrodes. As indicated by voltammetry, the switching voltage and ion-storage capacity fit the electrochromic switching of nickel oxide, undergoing a similar reaction. Because of its properties, manganese oxide, once stabilized, may serve as a counter-electrode for an electrochromic nickel oxide device.
TL;DR: In this article, a DC magnetron reactive sputtering of an indium-tin target using argon-oxygen-hydrogen sputter gas mixtures is described, which significantly broadens the process window for production of transparent ITO of resistivity −3 Ω cm for substrate temperatures 20 −200°C.
Abstract: Transparent conducting indiumtinoxide films have been produced by DC magnetron reactive sputtering of an indiumtin target using argonoxygenhydrogen sputter gas mixtures. The addition of hydrogen to the sputtering gas significantly broadens the process window for production of transparent ITO of resistivity −3 Ω cm for substrate temperatures 20–200°C. For higher substrate temperatures (∼ 350°C) the process window is broadened slightly. Electrical and optical properties, and degradation of ITO films of various thickness deposited onto soda glass, silica and polyester are discussed in detail.
TL;DR: In this paper, a spray pyrolytic decomposition of a spray solution of SbCl3, SnCl4, CH3CH2, CH2OH, H2O and HClCl was used to obtain high transparent and conductive antimony-doped tin oxide films.
Abstract: Highly transparent and conductive antimony-doped tin oxide films were prepared by pyrolytic decomposition of a spray solution of SbCl3, SnCl4, CH3CH2, CH2OH, H2O and HCl. The effects of the parametric variations on the film characteristics and the influence on the growth rate were studied. It is shown that our reasonably inexpensive and simple spray pyrolysis system is suitable for obtaining thin films with reasonably satisfactory properties. To improve the overall performance, the system was designed such that the parameters that effect the formation of the films were effectively controlled. The film properties studied include the surface morphology, Hall effect, electrical conductivity, optical transmission in the visible region and band gap. The experimental conditions necessary to obtain films with optimum characteristic features were successfully determined. Films with fairly high optical transmission (> 85% between 450 and 800 nm), low resistivity (∼10 −3 Ω cm ) and a direct band gap, Eg ≈ 3.82 eV, were obtained at about 430°C substrate temperature, Ts, with a relatively high deposition rate and good crystallinity.
TL;DR: The concentration of hydrogen and lithium ions in colored and bleached WO3 polycrystalline films was measured by secondary ion mass spectroscopy (SIMS) depth profile analysis and inductively coupled plasma mass spectrography as discussed by the authors.
Abstract: The concentration of hydrogen and lithium ions in colored and bleached WO3 films was measured by secondary ion mass spectroscopy (SIMS) depth profile analysis and inductively coupled plasma mass spectroscopy. X-ray analysis revealed that as-prepared WO3 films changed to a mixture of WO3 and tungsten bronze ( H x WO 3 or Li x WO 3 ) during the electrical coloration process. Poly-AMPS, 10% H2SO4 aqueous solution, and 1M LiClO4-propylene carbonate (PC) were used as the electrolytes. The crystal structure of colored films changed back to the initial state when the films were bleached, even though a large quantity of hydrogen or lithium atoms still remained inside bleached films. We proposed that a fraction of hydrogen or lithium cations will bind on optically inactive sites, possibly the grain boundaries of the WO3 polycrystalline film in the bleaching process, and will not contribute to the coloration.
TL;DR: In this paper, the spectral properties of some luminescent dyes, derivatives of xanthene and benzoxazinone groups, in a liquid polymer matrix, Triton x-100, have been studied.
Abstract: Spectral characteristics of some luminescent dyes, derivatives of xanthene and benzoxazinone groups, in a liquid polymer matrix, Triton x-100, have been studied. It is seen that Triton x-100 could serve as a suitable liquid matrix for the luminescent solar concentrators (LSCs).
TL;DR: In this article, the growth and texture of RF-sputtered cadmium sulfide thin films were investigated using the X-ray diffraction technique, and the results showed that the film quality is very sensitive to the argon pressure in the deposition chamber, heating the substrate at 200°C enhances the degree of preferential orientation, and higher substrate temperatures increase the stacking fault density in the grains.
Abstract: The growth and the texture of RF-sputtered cadmium sulfide thin films are investigated using the X-ray diffraction technique. The results show that: (1) the film quality is very sensitive to the argon pressure in the deposition chamber, (2) heating the substrate at 200°C enhances the degree of preferential orientation, and (3) higher substrate temperatures increase the stacking fault density in the grains. The sizes of crystallites are estimated from the reflection widths, and an analytical model for grain orientation is proposed.
TL;DR: In this article, an organic electrochemical deposition technique for preparation of coherent and uniform CdS thin films with oriented crystalline structure is described under the conditions of high Cd2+ ion concentrations (> 0.075M) and high deposition currents (>62; 5 mA/cm2).
Abstract: An organic electrochemical deposition technique for preparation of coherent and uniform CdS thin films with oriented crystalline structure is described. Under the conditions of high Cd2+ ion concentrations (> 0.075M) and high deposition currents (>62; 5 mA/cm2) void free films with crystallite sizes ∼ 0.5 μm having a preferred c-axis orientation are deposited for solar cell application. The film composition is stoichiometric and invariant with deposition variables. Deposition occurs by a cathodic reaction of deposited Cd with S through a bielectronic exchange process. On deposition from low Cd electrolytes ( 8 3 electron process. Non-linear growth kinetic behaviour reveals importance of extrinsic reactions like physico-adsorption involving S82− and S62− ionic species in determining the structural development of CdS films. CdS film resistivity ranges between 107 and 104 ω cm and depends on film thickness and electrolytic ratio of Cd and S ions.
TL;DR: In this article, the effect of the heat treatment as well as of the organic binders on the solid state and surface characteristics of the pyrrhotite powders and electrodes, has been analyzed by XRD, XPS and Mossbauer spectroscopy.
Abstract: Polycrystalline layers of pyrrohotite (Fe0.9S) mixed with PTFE and triton have been produced through a screen-printing method, followed by pressure and thermal (N2) treatments. The effect of the heat treatment as well as of the organic binders on the solid state and surface characteristics of the pyrrhotite powders and electrodes, has been analysed by XRD, XPS and Mossbauer spectroscopy. The pyrrhotite electrodes showed behavior as photoactive n-type semiconductors giving rise to a photopotential of about 200 mV in I− and Fe2+ containing solutions. Although the electrochemical corrosion was greatly inhibited by PTFE, the presence of a photocorrosion process was monitored at the illuminated electrode in presence of the redox electrolytes. A discussion is given as to explain the electrode behavior. Hypotheses related with its structure property are made.