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This paper is focused on the basic study and optimization of short time (

Laboratory studies were conducted in a cube-shaped reactor with the aim of generating and controlling homogeneous turbulence near the wall, with zero mean primary flow and minimal mean secondary flow motions, to achieve a homogeneous electrodeposition process. Turbulence was generated by a jet array, divided into 4 sectors consisting of 16 jets each. Two-dimensional Laser Doppler Velocimetry measurements showed that a high turbulence level can be achieved but that the flow is dominated by steady mean motions on the scale of the tank size. Random activation of the four sectors using an appropriate timing can strongly improve the turbulence conditions compared with continuous activation of the four jet sectors. Random activation leads to suppression of steady mean motions and RMS values increase of 100%.

Inorganic semiconductors have properties that are notoriously difficult to control due to the deleterious impact of crystalline imperfections, and this is especially so in solar cells. In this work, it is demonstrated that materials grown using wet chemistry processes for the preparation of nanocristalline precursors can achieve the same performance as the best state of the art, namely conversion efficiencies above 11% with CuInS2. Interestingly, due to the growth process, the active material inherit a porous morphology that is shown to play a part in the performance and functionality of the active material. The new device morphology leads to a device operation closer to that of nanoscale organic interpenetrated solar cells or dye sensitized solar cells than to those of standard polycrystalline ones.

In the field of Cu(Ga,In)(S,Se) 2 photovoltaic technology, zinc sulphide based buffer layers prepared by Chemical Bath Deposition (CBD) have already demonstrated their potential to replace CdS. This paper aims on a better understanding of deposition mechanism of the Zn(S,O,OH) buffer layers. First, the influence of deposition parameters is studied from solution chemistry considerations by constructing solubility diagrams of ZnS, ZnO, and Zn(OH) 2 . Experimental studies are then carried out by the in situ quartz crystal microgravimetry (QCM) technique. A global equation for the growth rate is derived from these experiments. The morphology and composition of Zn(S,O,OH) films are then determined using scanning electron microscopy and X-ray photoelectron spectroscopy techniques. Electro-deposited-CIS/Zn(S,O,OH)/ZnO and co-evaporated-CIGS/Zn(S,O,OH)/ZnO cells were prepared with efficiencies similar to that of reference CBD CdS buffer layers.

The Raman scattering analysis of S-rich CuIn(S,Se) 2 layers produced by electrodeposition of CuInSe 2 precursors and annealing under sulphurising conditions shows the strong dependence of their crystalline quality on the annealing parameters. Worsening of the crystalline quality is reflected by the presence of an increasing contribution at the higher frequency side of the main Raman band. The comparison of these data with the solar cell parameters points out the existence of a correlation between the efficiency of the devices and the width of the mode. The dependence of the Raman spectra on differences in the process parameters with significant impact in the microcrystalline quality of the layers give interest to the use of Raman scattering as process assessment technique for device quality control.

A detailed Raman scattering analysis of the electrodeposition process of nanocrystalline CulnSe 2 layers for solar cell devices is reported. The correlation of the Raman spectra measured after the growth of the layers with different times has allowed investigating the chemical phases involved in the film formation process and their resulting nanocrystalline structure. The experimental data indicate the presence of elemental Se and Cu-Se binary compounds as the main secondary phases in the layers, which are directly related to the Se and Cu excess conditions used in the electrodeposition growth. These data show the existence of a high content of elemental Se at the region close to the interface of the layer with the Mo-coated glass substrate, this being likely related to a lack of incorporation of In at the initial growth stages. Nanoscopic Cu-deficient domains are also revealed by the presence of a band at the low frequency side of the main CulnSe 2 peak.

CuInSe2 thin films one-step electrodeposited under different conditions were studied by MicroRaman spectroscopy to identify and quantify the individual phases present in the films. From the analysis of the Raman spectra, the main ternary phase (CuInSe2) and elementary selenium Se0 were clearly identified. Specific chemical etches confirm the presence of elementary selenium Se0 and copper selenide binary phases CuxSe in selenium rich film. The amounts of these two phases were evaluated from X-ray Fluorescence measurements and confirmed using phase selective chemical treatments.

The CIS by electrodeposition (CISEL) project between Electricite de France (EDF), Centre National de la Recherche Scientifique (CNRS)/Ecole Nationale Superieure de Chimie de Paris (ENSCP) and Saint-Gobain Recherche (SGR) aims at developing a low-cost electrodeposition process for Cu(In,Ga)(S,Se) 2 (CIGS) solar cells. The process is characterized by two main steps: (i) deposition of the precursor film and (ii) thermal annealing. This process enables the preparation of a large range of sulfur containing absorbers, with S/(S+Se) atomic ratio from 0% to more than 90%. The films are single phase over the whole composition range. The influence of Sulfur content on the microstructure has been shown with grain sizes decreasing with increasing sulfur content. Efficient solar cells can be obtained from all the different precursor compositions, with efficiencies of over 10% on lab cells on sulfur-rich absorbers, and 6–7% on 30×30 cm 2 devices. The homogeneity of 15×15 cm 2 substrates is also discussed.

This paper reviews the state of the art in using electrodeposition to prepare chalcopyrite absorber layers in thin film solar cells. Most of the studies deal with the direct preparation of Cu(In,Ga)Se 2 films, and show that the introduction of gallium in the films is now becoming possible from single bath containing all the elements. Electrodeposition can also be used to form precursor films with stacked layer structures, of pure elements or of combinations with binary or even ternary films. Thermal annealing treatments are of dramatic importance to provide suitable electronic quality to the layers. They are often done in the presence of a chalcogen (selenium or sulfur) over pressure and there is a tendency to use rapid thermal processes. Less studies are devoted to complete solar cell formation. Significant progresses have been made in the recent period with several groups achieving cell efficiencies around 8–10% on different substrates. A record efficiency of 11.3% is reported for a cell with an absorber presenting a band gap of 1.47 eV. First results on the manufacturability of the corresponding process to large areas are presented.

French Pressurised Water Nuclear Reactors have steam generators made of Inconel 690, a nickel-base superalloy with high chromium and iron contents. Corrosion of this superalloy in primary water conditions may be reduced by a surface treatment of the tubes. The deposition of chromium onto Inconel 690 in cementation packs containing a chromizing mixture and a CrCl 3 activator is studied between 1273 K and 1523 K in sealed quartz tubes. At constant volume, liquid CrCl 2 is synthesised in the conditions used. Two layers are observed at 1273 K and 1323 K by metallographic observations. The composition of the outer layer is a thick a Cr-rich layer with 4.6 at% Ni and 1.7 at.% Fe. An inner diffusion layer also grows. It corresponds to a γ-Cr-Ni layer. At 1523 K, only the Cr-rich layer still grows and Kirkendall porosity appears. Growth rates of the Cr-rich layer are parabolic whatever the temperature. The rate-limiting step is very likely diffusion of chromium into the chromium-rich layer. Finally, oxidation tests were carried out in a loop simulating primary water conditions of Pressurized Water Reactor.

Two kinds of tantalum oxide films have been studied by XPS: dry and electrogenerated anodic oxides. XPS spectra of Ta4f and O1s have been used to determine the chemical composition of the different films. Ta2O5 is the main constituent of thick films (15 nm≤dox≤60 nm), although the concomitant presence of sub-oxides (mainly TaO) is observed. In thin films (dox

Deposited activity on PWR equipment and component surfaces sometimes has to be decontaminated. An appropriate method for the dissolution of contaminated chromium-rich grow-on oxides uses an alternation of oxidizing steps (generally alkaline permanganate) and a reducing step made of organic acids. These organic acids have simultaneously reducing and chelating properties. Then, chelates are destroyed on cation exchangers in the H+ form and the resulting acids are oxidized with the permanganate of the first step. Basic information on chemical properties important in these three steps has been determined: acid-base properties of the considered organic acids, stability constants of the complexes formed between these acids and the metal cations originating from the stainless steel constituents (Fe, Ni, Cr, Co), ion exchange process, oxidation of the organic acids with emphasis on various products generated before the final products (CO2, H2O).

The electrochemical behaviour of Ta-TaO x structures was investigated by impedance spectroscopy. It was shown that, after the polishing treatment, the electrode is covered by an “initial” oxide film containing tantalum monoxide, TaO, and that “electrogenerated” oxides are only composed of tantalum pentoxide, Ta 2 O 5 (⩾ 97 mol%). However, the dielectric properties of the structures strongly depend on the thickness of the oxide, d ox , because of the influence of a sub-stoichiometric oxide of TaO in thin layers, in agreement with previous results obtained by XPS measurements. The variation of the reciprocal total capacitance of the oxide, C ox , with the quantity of electricity, Q a , involved in the formation of the oxide exhibits two linear parts. The breakdown of the slope of that curve is interpreted by a variation of the relative permittivity, e r , of the oxide with its thickness: for thin films ( d ox ⩽ 19nm), ϵ r ≈ 18.5 and for thick films ( d ox > 19 nm) ϵ r ≈ 27.5.

International audience; Electrodeposited CuInSe2 thin films are of potential importance, as light absorber material, in the next generation of photovoltaic cells as long as we can optimize their annealing process to obtain dense and highly crystalline films. The intent of this study was to gain a basic understanding of the key experimental parameters governing the structural-textural-composition evolution of thin films as function of the annealing temperature via X-ray diffraction, scanning/transmission electron microscopy and thermal analysis measurements. The crystallization of the electrodeposited CuInSe2 films, with the presence of Se and orthorhombic Cu2−xSe (o-Cu2−xSe) phases, occurs over two distinct temperature ranges, between 220 °C and 250 °C and beyond 520 °C. Such domains of temperature are consistent with the melting of elemental Se and the binary CuSe phase, respectively. The CuSe phase forming during annealing results from the reaction between the two secondary species o-Cu2−xSe and Se (o-Cu2−xSe+Se→2 CuSe) but can be decomposed into the cubic β-Cu2−xSe phase by slowing down the heating rate. Formation of liquid CuSe beyond 520°C seems to govern both the grain size of the films and the porosity of the substrate-CuInSe2 film interface. A simple model explaining the competitive interplay between the film crystallinity and the interface porosity is proposed, aiming at an improved protocol based on temperature range, which will enable to enhance the film crystalline nature while limiting the interface porosity.

Les proprietes de transfert electronique aux interfaces "M.I.E." (Metal/Isolant/Elec trolyte) ont ete mises en evidence en s'appuyant sur l'exemple significatif du tantale. Ce metal, recouvert d'une couche passivante d'oxyde Ta2 O5 , a ete etudie en presence du couple Fe (II)/Fe (III) en solution. Par ailleurs, le depot a l'interface d'un metal noble tel que le platine genere une structure "M.I.M." (Metal/Isolant/Metal) qui possede des proprietes de conduction remarquables. Le comportement electrochimique de cette "electrode modifiee" en presence d'un couple redox en solution est tres voisin de celui d'une electrode de platine pur.

This article reports a detailed Raman scattering and microstructural characterization of S-rich CuIn(S,Se)2 absorbers produced by electrodeposition of nanocrystalline CuInSe2 precursors and subsequent reactive annealing under sulfurizing conditions. Surface and in-depth resolved Raman microprobe measurements have been correlated with the analysis of the layers by optical and scanning electron microscopy, x-ray diffraction, and in-depth Auger electron spectroscopy. This has allowed corroboration of the high crystalline quality of the sulfurized layers. The sulfurizing conditions used also lead to the formation of a relatively thick MoS2 intermediate layer between the absorber and the Mo back contact. The analysis of the absorbers has also allowed identification of the presence of In-rich secondary phases, which are likely related to the coexistence in the electrodeposited precursors of ordered vacancy compound domains with the main chalcopyrite phase, in spite of the Cu-rich conditions used in the growth. This points out the higher complexity of the electrodeposition and sulfurization processes in relation to those based in vacuum deposition techniques.

This paper describes the detailed microstructral characterisation of S-rich CuIn(S,Se)2 absorbers fabricated by single step electrodeposition (ED) of nanocrystalline CuInSe2 precursors followed by rapid thermal annealing under sulphurising conditions. This has allowed identifying the main secondary phases in the precursors as elemental Se, CuSe and Cu2Se. The Raman spectra from these precursors also show the presence of Cu-poor OVC domains, which contrasts with the Cu-rich conditions used in the ED growth. This has been related to the presence in the annealed layers of In rich secondary phases, which lead to a slightly Cu poor composition. Moreover, the used sulphurising conditions also lead to the formation of a relatively thick MoS2 layer between the absorber and the Mo back contact. The high microcrystalline quality of the layers is likely responsible of the relatively high efficiency value of 11% of the solar cells fabricated with these absorbers.

CuInSe2 and Cu(In, Ga)Se2 precursor layers have been prepared by electrodeposition, with morphologies suitable for device completion. These precursor films were transformed into photovoltaic quality films after thermal annealing without any post-additional vacuum deposition process. Depending on the preparation parameters annealed films with different band gaps between 1eV and 1.5 eV have been prepared. The dependence of resulting solar cell parameters has been investigated. The best efficiency achieved is about 10,2 % for a band gap of 1.45 eV. This device presents an open circuit voltage value of 740 mV, in agreement with the higher band gap value. Device characterisations (current-voltage, capacitance-voltage and spectral response analysis) have been performed. Admittance spectroscopy at room temperature indicates the presence of two acceptor traps at 0.3 and 0.43 eV from the valance band with density of the order of 2. 1017 cm-3 eV-1.

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cVA fur Wasserbau/Hydrologie/Glaziologie, 8092 Zurich, Switzerland Randomly firing jet arrays can be used for large-scale electrodeposition from dilute solutions for which tertiary current distribution prevails, for example, the electrodeposition of Cu‐In‐Se layers, which are promising compounds for thin-layer solar devices. For this type of electrodeposition, a stirring system is needed to enhance the mass-transfer rate toward the cathode. The studied stirring system is a modular jet array firing in the horizontal direction, submerged in the tank containing the electrolyte. A dilute Cu electrolyte was used to investigate and optimize the hydrodynamic conditions determined by the stirring system. Two parameters were investigated to vary the hydrodynamic conditions: the mesh of the jet nozzles and the distance between the jet nozzles and the cathode. An optimized configuration was found, allowing the jets to merge and create a homogeneous tertiary distribution. Random sequential activation of the jets was used with the optimized configuration, and the resulting copper layer exhibited higher homogeneity than those resulting from continuous activation of the jets.

The first stages of the electrochemical deposition of a Cu-In-Se compound on molybdenum-coated glass were investigated. The surface morphology was examined after various deposition times by a field emission gun-scanning electron microscope. The surface composition and chemical environment analysis were characterized by X-ray photoelectron spectroscopy (XPS). Raman spectroscopy, X-ray diffraction, and X-ray fluorescence were also performed. This enabled the growth steps to be evidenced. A quasi-instantaneous three-dimensional nucleation occurs. The first nuclei are made of a copper-rich Cu-Se phase without indium. Codeposition of indium starts when the Se/Cu surface ratio reaches a value close to 1, which confirms that the formation of a Cu-Se phase is a prerequisite for indium incorporation. With increasing the deposition time, the In/Cu surface ratio increases and tends to a constant value close to 0.5, smaller than the bulk value. The Se/Cu ratio increases first rapidly and then more slowly, when coalescence of the nuclei has occurred. XPS analysis shows that this two-step behavior corresponds to an evolution of the chemical environment of the Se species, indicating the presence of several Se compounds in the film. X-ray diffraction and Raman spectroscopy confirm the presence of a Cu-Se phase and elemental Se, in addition to the predominant chalcopyrite phase.

Surface reactions of molybdenum-covered glass plates, used as back contact for thin Cu(In,Ga)(S,Se) 2 solar cells, are examined at open circuit in acidic electrolytes used for plating CuInSe 2 layers. A multinary element cementation reaction occurs, leading to the corrosion of molybdenum and the formation of CuSe x electroless deposit (x from 0.2 to 0.8), with well-defined compositions. Immediately after immersion, small nuclei appear on the surface, which then grow to form a quasi-continuous layer. The time evolution of the open-circuit potential of Mo and the Se/Cu surface atomic ratio are correlated and are in agreement with thermodynamic data predictions.

The electrochemical behavior of polycrystalline molybdenum thin films in contact with acidic aqueous solutions containing Cu(II), In(III), and Se(IV) species was investigated. The substrate and solutions are used for the electrodeposition of CuInSe 2 films in the field of photovoltaics. The chemical interaction between Mo electrode and the electrolyte at the initial steps of immersion is studied by in situ electrochemical measurements of the time evolution of the open-circuit potential. Ex situ field emission gun-scanning electron microscope observations for morphological investigations, X-ray photoelectron spectroscopy for surface composition, and chemical environment analysis was carried out. Raman spectroscopy, X-ray diffraction, and X-ray fluorescence were also performed. It is shown that molybdenum undergoes electrochemical cementation reactions associated with a characteristic potential increase with immersion time. Immediately after immersion, small nuclei of Cu-Se deposits appear on the surface, which then grow to form a quasi-continuous layer after 400 s. The chemical composition of the layer evolves with immersion time. No indium is incorporated. The global composition changes from a Se/Cu atomic ratio close to 0.3 to a ratio close to 0.7. The final layer contains at least two phases, i.e., umangite Cu 3 Se 2 and CuSe. These complex evolutions are discussed in terms of competing electrochemical reactions and thermodynamic considerations.

The behavior of sputter deposited polycrystalline thin films of molybdenum covered glass plates, used as standard back contact for thin Cu(In, Ga)(S,Se)2 solar cells is examined while in contact with acidic aqueous solutions containing Cu(II), In(III) and Se(IV) species at open circuit potential. These solutions are used for the electrodeposition of CuInSe2 thin films. An electrochemical investigation was carried out, in combination with SEM-FEG observations, Raman spectroscopy and XPS surface analysis. It is shown that molybdenum undergoes an electrochemical cementation reaction. Its potential increases with immersion time. Immediately after immersion, small nuclei appear on the surface, which then grow to form a quasi-continuous layer after 600s. The chemical composition of the layer evolves with immersion time. No indium is incorporated. Cu-Se phases are formed whose composition changes from Se/Cu > 0.3 to a Se/Cu atomic ratio ~ 0.7. The final layer contains two phases, Umangite Cu3Se2 and CuSe.

Corrosion-oxide layers are formed in pressurized water at 633 K on Zr and Zr-1.4% Sn (Zircaloy 4) during 476 and 590 days, respectively. Oxidation is continuously monitored in situ with impedance spectroscopy (IS), and results are compared to ambient temperature impedance. IS confirms at both materials an acceleration of corrosion after the initial phase of parabolic to cubic growth. At Zr-1.4% Sn, accelerated corrosion consists of cycles of little attenuation and about 80 days cycle time following the first cubic period. At unalloyed Zr, where corrosion is slower, acceleration begins after 360 days. IS at Zr-1.4% Sn shows a cyclic evolution/annihilation of one of the two oxide relaxations which traces a bilayer evolution: (i) formation of a protective (sub)layer at the metal/oxide side to a critical thickness, (ii) conductivity increase in that layer during stress relief, and (iii) regrowth of a protective sublayer into the metal. Such behavior is confirmed by scanning electron microscopy micrographs which identify sublayers separated by crack layers. Thickness of the protective layer is estimated from IS. Degradation at the end of each cycle occurs gradually (∼15 days at Zr-1.4% Sn). Reasons for accelerated corrosion at degraded layers, such as a formation of open porosity soaked with liquid, are discussed. Dielectric and ac conduction loss terms at 633 K dominate impedance up to high frequencies. IS results indicate that higher loss terms in the outer layer reflect solid-state properties of the oxide rather than a liquid soaking of pores or interfacial roughness.

This paper reports the microstructural analysis of S-rich CuIn(S,Se)2 layers produced by electrodeposition of CuInSe2 precursors and annealing under sulfurizing conditions as a function of the temperature of sulfurization. The characterization of the layers by Raman scattering, scanning electron microscopy, Auger electron spectroscopy, and XRD techniques has allowed observation of the strong dependence of the crystalline quality of these layers on the sulfurization temperature: Higher sulfurization temperatures lead to films with improved crystallinity, larger average grain size, and lower density of structural defects. However, it also favors the formation of a thicker MoS2 interphase layer between the CuInS2 absorber layer and the Mo back contact. Decreasing the temperature of sulfurization leads to a significant decrease in the thickness of this intermediate layer and is also accompanied by significant changes in the composition of the interface region between the absorber and the MoS2 layer, which becomes Cu rich. The characterization of devices fabricated with these absorbers corroborates the significant impact of all these features on device parameters as the open circuit voltage and fill factor that determine the efficiency of the solar cells.

This paper presents the influence of the solution chemistry of chemical bath deposition (pH and complexing agents) on the performance of CuIn(S,Se)2 cells after an initial CN treatment. It is shown that it is possible to modify the deposition conditions of the CdS by increasing the pH of the solution and by replacing the complexing agent (ammonia) by citrate ions. Both NH3 based and citrate based process give very homogenous and covering thin films. However, in the case of the citrate based process a decrease of open circuit voltage (Voc) and fill factor (FF) and thus of the cell efficiencies is observed. This points out that the main role of the buffer layer is not only related to the specific properties of the CdS itself but also to the near surface modifications of the CuIn(S,Se)2 caused by the presence of the complexing agent in the bath.