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Materials Research Bulletin 01/2012; in press, corrected proof. · 2.11 Impact Factor
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ABSTRACT: Electrodeposited
samples have been used as substrates for CdS growth from alkaline solutions where the ratio of thiourea,
or TU, to cadmium sulfate,
has been varied systematically from 10 to 100. Analysis of the
surface and interface chemistry as a function of the CdS bath deposition conditions has been performed by X-ray photoelectron
spectroscopy. An increase in the
surface coverage, without appreciable
chemical modifications, can be obtained by increasing the thiourea to cadmium sulfate proportion in the CdS growth solution.
As this
ratio increases, the proportion of
and
secondary phases detected on the
samples decreases with respect to water and the main CdS compound, but carbonate and cyanamide impurities incorporation increases
at the near-surface region. © 2001 The Electrochemical Society. All rights reserved.
Journal of The Electrochemical Society. 10/2001; 148(11):G602-G606.
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ABSTRACT: Thin film solar cells of CuInS2/Zn(Se,O)/ZnO configuration have been studied as a function of the Zn(Se,O) buffer layer deposition parameters. Deposition of the buffer films was carried out by the chemical bath deposition (CBD) method, at different bath temperatures and compositions, and followed in situ with a quartz crystal microbalance. The CBD conditions were chosen to grow Zn(Se,O) buffer layers under different kinetic regimes but maintaining the same buffer thickness. The cells have been characterised with current-voltage and quantum efficiency measurements. Light soaking effects and medium term stability have been checked. It is found that Zn(Se,O) grown under predominant electroless kinetics gives rise to buffer films richer in oxygen, which allow for higher fill factors, higher efficiencies (around 10%) and stability of the cells. These cells show however lower open circuit potential. On the other hand, Zn(Se,O) buffers grown under chemical regime become richer in selenium, which gives rise to cells with higher open circuit potential, but lower fill factor, conversion efficiency and stability. Light soaking effects are also more important with the chemically grown buffers.
MRS Proceedings. 12/2000; 668.
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ABSTRACT: X-ray photoelectron spectroscopy analysis of ZnSe thin films deposited by the chemical bath deposition method is carried out. The composition of the films at the surface and subsurface is determined by angle-resolved XPS detection of photoelectrons, and the elemental profile in the whole depth is determined by sputter-assisted XPS. In general, the films are composed of a mixture of ZnSe and ZnO (or Zn(OH)2 for non-annealed films), the relative proportions of which vary depending on the substrate properties and thermal treatments. Also, inhomogeneous depth composition is encountered, the films richer in ZnO being close to the film/substrate interface, with increasing ZnSe proportion above. This result is explained in relation to the mechanisms that contribute to film growth in the chemical bath. The characteristic composition of the films is expected to influence their behaviour as buffer layers for photovoltaic thin-film solar cells. Copyright © 2000 John Wiley & Sons, Ltd.
Surface and Interface Analysis 09/2000; 30(1):522 - 526. · 1.18 Impact Factor
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ABSTRACT: Many papers have been published lately on chemical bath deposition of CdS (CBD‐CdS) thin films and related materials due to
the promising results obtained using CBD‐CdS for the fabrication of thin‐film solar cells. In spite of this little of the
research proposes a realistic chemical mechanism for the deposition process based on the determination of kinetic parameters.
In this paper we present an exhaustive study of the CBD‐CdS kinetic from which we propose a new chemical mechanism which agrees
with the kinetic parameters determined supported by heterogeneous catalysis concepts. Simultaneously, the dependence of the
deposited film structure on the kinetic variables is studied and the results obtained corroborate the proposed mechanism.
These studies have allowed us to stablish a standard set of conditions for the fabrication of homogeneous and continuous very
thin CdS films.
Journal of The Electrochemical Society. 10/1997; 144(11):4081-4091.
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ABSTRACT: Chemical‐bath deposition of
thin films from
solutions has been studied. The effect of various process parameters on the growth and the film quality is presented. A first
approach to a mechanistic interpretation of the chemical process is reported. The structural, optical, chemical, and electrical
properties of the
thin films deposited by this method have been studied. The electron diffraction (EDS) analysis shows that the films are microcrystalline
with a cubic structure. EDS analysis has demonstrated that the films are highly stoichiometric. Scanning electron microscopy
studies of the
thin films deposited by this method show that the films are continuous and homogeneous. Electrical conductivity measurements
have shown the highly resistivity nature of these films
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Journal of The Electrochemical Society. 12/1993; 141(1):205-210.
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ABSTRACT: Indium hydroxy sulphide thin films have been deposited from an acidic bath using indium (III) chloride, thioacetamide and acetic acid as complexing agent. It has been found that the proper control of deposition conditions significantly influences the film quality and reproducibility as well as the film thickness. XPS measurements have been carried out for samples prepared using different reactant concentrations in order to study variations in the surface composition. Some films have been also air-annealed at 300 and 400°C to know in which way the composition is affected by this processing. Films are formed by indium hydroxy sulphide, indium oxide and indium sulphate having contaminant species adsorbed on the surface. All samples annealed have shown an oxygen incorporation from the air and an important sulphur loss. The S/In atomic ratio in the indium hydroxy sulphide compound is about one for the non-annealed samples showing that the compound is sulphur deficient. When samples are annealed at 400°C, this value is decreased down to 0.3 owing to the formation of sulphur containing volatile species. The molecular formula for the indium hydroxy sulphide as deposited can be close to InOHS with slight variation in the OH:S proportion depending on the deposition conditions and the annealing temperature.
Thin Solid Films 353:100-107. · 1.89 Impact Factor
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ABSTRACT: The leveling capability of sol–gel SiO2 layers onto titanium and Kovar (Fe54 Ni29 Co17) foil substrates has been analyzed by atomic force microscopy (AFM) and profilometer roughness measurements as a function of the sol–gel preparation parameters. SiO2 coatings have been prepared by immersion of metallic foils in a solution where the [alkoxide]/[EtOH] ratio was between 0.05 to 0.7, and subsequent withdrawal of the samples at a constant rate between 8 and 49 cm/min. By increasing the [alkoxide]/[EtOH] ratio and/or the withdrawal velocity, the SiO2 layer thickness and leveling capability increase but its mechanical integrity decreases. By increasing SiO2 film thickness, better coverage of large-scale heterogeneities but poorer coverage of short-scale features have been observed. A compact (cracks and striations free) coverage which minimizes the roughness sample surface at short and large scales has been obtained by applying successive SiO2 layers with various thicknesses.
Surface and Coatings Technology 138:205-210. · 1.87 Impact Factor
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ABSTRACT: The growth of indium(III) sulphide thin films from aqueous thioacetamide (TA)–In(III) solution has been studied with a quartz crystal microbalance (QCM). It is found that the growth of the film consists in the parallel deposition of In2S3 and In2O3. Both processes are induced by sulphide anions (S2−) produced after decomposition of thioacetamide. In2S3 is deposited by precipitation of crystallites formed in the bulk solution. On stirred solutions this reaction is hindered due to the disruption of the nucleation centres. On the other hand, In2O3 is deposited by electrochemical reduction of naturally dissolved oxygen (O2) by the S2− anions, followed by chemical reaction with In3+. This process is of electroless-chemical nature and has important consequences on the properties of the films. Both reaction mechanisms, chemical and electroless-chemical, compete under different experimental conditions: temperature, solution composition, stirring. For instances, the deposit of In2O3 is favoured at low bath temperature, in aerated solutions, giving rise to films with higher oxide proportion. Additives like hydrochloric acid and acetic acid also favour In2O3 deposition. The system has easy possibility to tune chemical and physical properties of the films, like composition, transparency and absorption edge, of interest for photovoltaic applications.
Electrochimica Acta. 49(5):737-744.
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ABSTRACT: The structure, morphology and optical properties of copper indium sulfide thin films prepared by a novel modulated flux deposition procedure have been investigated for layers from 200 to 400 nm thickness. These polycrystalline CuInS2 films grown onto glass substrates showed CuAu-like structure, similar to epitaxial CuInS2 films grown onto monocrystalline substrates, and direct band gap values Eg=1.52–1.55 eV, optimum for single-junction photovoltaic applications. The increase in the layer thickness leads to growth of the average crystallite size and increases slightly the surface roughness and the absorption coefficient.
Thin Solid Films · 1.89 Impact Factor
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ABSTRACT: Thin film solar cells based on CuInS2/buffer/ZnO have been prepared with different buffer layers of mixed ZnS-In2S3 composition. The buffer films are grown by chemical bath deposition (CBD) from acidic solutions of InCl3, ZnSO4 and thioacetamide (TA). A kinetics study of the growth of the buffer layers is carried out with the quartz crystal microbalance. The influence of bath conditions (solution, temperature and composition) on the growth rate is studied. Films are obtained with different physical, chemical and morphological properties. The absorption coefficient spectra of the films show a variation depending on the CBD conditions, with absorption edges between 2.6 and 3.35 eV. Surface morphology of the films, observed with scanning electron microscopy, reveals that the presence of Zn produces characteristic structures with microtubular form, compared with pure In2S3 buffer films. Solar cell results show a significant increase of Voc and FF upon introducing Zn2+ ion in the buffer layer.
Thin Solid Films 515(15):6036-6040. · 1.89 Impact Factor
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ABSTRACT: The electrochemical quartz crystal microbalance (EQCM) has been used to study the growth of CuInS2 films by one-step electrodeposition. Films have been grown on SnO2/glass substrate from aqueous solutions of In2(SO4)3, CuSO4, and Na2SO3. Differences in the properties and structure of the CuInS2films are observed depending on the deposition potential and concentration of precursors. X-ray diffraction shows a CuInS2 phase predominant for films, after annealing at 200 °C in nitrogen atmosphere. The composition of the films was studied with X-ray photoelectron spectroscopy (XPS), showing again predominant CuInS2, together with secondary phases of Cu2O/Cu2S, CuO/CuS, and In2S3 compositions.
Thin Solid Films.
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Boletín de la Sociedad Española de Cerámica y Vidrio, ISSN 0366-3175, Vol. 43, Nº. 2, 2004 (Ejemplar dedicado a: VII Reunión Nacional de Materiales), pags. 367-369.
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ABSTRACT: The chemical bath deposition of Cd1 − xZnxS thin films has been attempted following the usual methods employed for the chemical bath deposition of CdS and ZnS. The films obtained show compositions which vary almost linearly with the bath composition variation. However, the formation of a unique phase does not seem to be possible by this method, rather, the films seem to be composed of ZnS, CdS and Cd1 − xZnxS with an x value of 0.7 for all the bath compositions. The films obtained by this method have been characterized showing properties among the range found for pure CdS and ZnS, however the ZnS deposition process, which is slower than that of CdS, seems to dominate the deposition process.
Thin Solid Films.
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ABSTRACT: The influence of CdS thickness and TCO deposition condition on the optoelectronic, morphological and structural properties of CdSTCO bilayers has been studied. CdS was deposited by chemical bath, whereas the TCOs (ITO and aluminium-doped ZnO) were prepared by rf-magnetron sputtering. Cadmium sulphide thickness below 0.1 μm have been found to be optimal for avoiding optical absorption losses and conductivity deterioration. Though both types of window coatings, with TCO made at 25 and 200°C, have good quality, the ITO-based samples have shown a higher infrared transmission than those based on ZnO. Additionally, 10 and 70 minutes air-annealing treatments at 200°C have been carried out. Their analysis has demonstrated that the shorter ones are more suitable for enhancing structure maintaining unchanged electro-optical characteristics.
Solar Energy Materials and Solar Cells.
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ABSTRACT: The influence of deposition parameters on optoelectronic and structural properties of Sn-doped In2O3 thin films grown by r.f. magnetron sputtering has been investigated. Two different targets, ( at.%) and In2O3:SnO2 () have been studied in order to compare resulting samples and try to reduce the substrate temperature down to room temperature. By using the target, transparent conductive indium tin oxide has been obtained at a substrate temperature of 400 °C, with T = 80–90% and p~ 10−4 Ω cm. Meanwhile, low sheet resistance, 5–15 Ω/□, and high transmittance in the visible range, 80–90%, have been measured for ITO coatings made at room temperature with the oxidized target, by introducing very low O2 mass-flow rates in the sputtering chamber.
Thin Solid Films.
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ABSTRACT: Thin film solar cells based on CuInS2/ZnS/ZnO have been prepared with ZnS buffer film of different thickness. ZnS films are grown by chemical bath deposition (CBD) from acidic solutions of ZnSO4 and thioacetamide (TA). The change of the growth rate with time is studied by means of the quartz crystal microbalance. Films with different thickness show variable physical, chemical and morphological properties. The structure is studied with X-ray diffraction, showing different crystallinity with deposition time. The absorption coefficient depends also on the CBD deposition time, and shows absorption edges between 2.70 and 3.65 eV. The compositional analysis carried out with XPS (surface) and EDAX (bulk). Bulk composition reflects highly stoichiometric films, with Zn/S ratios close to unit. Preliminary results with CuInS2-based solar cell show efficiencies around 5%, lower than usually found with standard CdS buffer films (around 9%).
Solar Energy Materials and Solar Cells.
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ABSTRACT: The influence of cadmium salt and thiourea concentrations on the morphological and structural properties of chemical bath-deposited CdS thin films has been investigated. Two different feature regimes have been distinguished: an inner continuous layer grown directly on the glass and independent on the deposition conditions, and other porous overlayer, more dependent on the chemical concentrations. Root mean square, RMS, and average roughnesses, Ra, as quantified by AFM, are about 10–13 nm and 7–11 nm, respectively, for all CdS samples tested. These films are sulphur-poor, decreasing S/Cd atomic ratio from 0.82 at low cadmium salt, 1 mM, and high thiourea concentrations, 100 mM, down to 0.76 at higher [Cd2+], 5 mM, and lower [TU], 10 mM.
Applied Surface Science.
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ABSTRACT: Thin film solar cells based on CuInS2 buffer ZnO have been prepared with different buffer layers of mixed ZnS In2S3 composition. The buffer films are grown by chemical bath deposition CBD from acidic solutions of InCl3, ZnSO4 and thioacetamide TA . A kinetics study of the growth of the buffer layers is carried out with the quartz crystal microbalance. The influence of bath conditions solution, temperature and composition on the growth rate is studied. Films are obtained with different physical, chemical and morphological properties. The absorption coefficient spectra of the films show a variation depending on the CBD conditions, with absorption edges between 2.6 and 3.35 eV. Surface morphology of the films, observed with scanning electron microscopy, reveals that the presence of Zn produces characteristic structures with microtubular form, compared with pure In2S3 buffer films. Solar cell results show a significant increase of Voc and FF upon introducing Zn2 ion in the buffer layer
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ABSTRACT: Thin film solar cells based on CuInS2 ZnS ZnO have been prepared with ZnS buffer film of different thickness. ZnS films are grown by chemical bath deposition CBD from acidic solutions of ZnSO4 and thioacetamide TA . The change of the growth rate with time is studied by means of the quartz crystal microbalance. Films with different thickness show variable physical, chemical and morphological properties. The structure is studied with X ray diffraction, showing different crystallinity with deposition time. The absorption coefficient depends also on the CBD deposition time, and shows absorption edges between 2.70 and 3.65 eV. The compositional analysis carried out with XPS surface and EDAX bulk . Bulk composition reflects highly stoichiometric films, with Zn S ratios close to unit. Preliminary results with CuInS2 based solar cell show efficiencies around 5 , lower than usually found with standard CdS buffer films around 9
