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

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.

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

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.

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.

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.