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26th European Photovoltaic Solar Energy Conference and Exhibition; 2489-2491, Tungsten-doped indium oxide (IWO) thin films were deposited at 350 with varying growth rates in the range of 0.01–0.04 nm/s by the reactive electron beam vapor technique and microstructure, optical and electrical properties of these IWO thin films were investigated in detail. High purity In2O3:WO3 ceramic targets and oxygen gas are used as source materials. Firstly, one 20 nm-thickness IWO buffer layer was fabricated on common glass substrate by electron beam vapor deposition at the low growth rate of ~0.01 nm/s. Secondly, the other subsequent 60 nm-thickness IWO film was fabricated on the above buffer layer via the same deposition technique at relatively higher growth rate of ~0.04 nm/s. Typical glass/IWO thin film performances with gradual growth rate: Resistivity, p~5.05×10-4 Ωcm; electron concentration, n~1.84×1020 cm-3; electron mobility, μ~67.1 cm2V-1s-1; optical transmittance in the visible and near infrared region, T~75-89%. The optical and electrical properties of IWO thin films obtained with gradual rates deposition are superior to those thin films with normal growth process. The high mobility IWO thin films are promising TCO materials applied in nip type μc-Si:H thin film solar cells and a-Si:H /μc-Si:H tandem solar cells.

26th European Photovoltaic Solar Energy Conference and Exhibition; 2482-2484, The micro-structural, electrical and optical properties of textured surface boron doped zinc oxide (ZnO:B) thin films and ZnO:B on tungsten doped indium oxide (In2O3:WO3, IWO) coated glass (glass/IWO/ZnO:B) were investigated in this work. ZnO:B thin films were directly grown via low pressure metal organic chemical vapor deposition (LP-MOCVD) at low temperature of ~150 . The IWO thin films were deposited by the reactive electron beam vapor technique. High purity diethylzinc (DEZn) and H2O were used as source materials, and diborane (B2H6) was used as an n-type dopant gas. The gradual doping growth (GDG) techniques are applied in LP-MOCVD ZnO:B thin films process. The IWO/ZnO:B thin films exhibit rough pyramid-like surface morphology with high total transparencies and excellent electrical properties as well as improved diffuse transmittance. These ZnO:B and IWO/ZnO:B thin films are promising TCO layers applied as substrates for silicon-based thin film solar cells.

26th European Photovoltaic Solar Energy Conference and Exhibition; 2479-2481, Hydrogenated Ga-doped ZnO (ZnO:Ga/H, GZO/H) transparent conductive oxides (TCOs) thin films are deposited on glass substrates via pulsed direct-current (DC) magnetron sputtering at room temperature. The influences of H2 flow rates ranged from 0 sccm to 12 sccm on the micro-structural, electrical, and optical properties of GZO/H TCO thin films are investigated. The GZO/H thin films show rather lower resistivity with relatively higher carrier concentration and electron mobility, and also present higher transmittance in visible range (~400-600 nm) than the GZO thin films. These GZO/H thin films exhibit high transparencies of ~80-95% for wide spectral region (~ 380-1000 nm). The optimized GZO/H thin film obtained at 6 sccm exhibits the lowest resistivity 6.8×10-4 Ωcm with a high electron mobility of 34.2 cm²/Vs. These GZO/H thin films are also developed for rough textured surface with post wet-etching process in diluted hydrochloric acid. The formation model for textured surface GZO/H thin films is introduced.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 3049-3051, Textured surface aluminum doped zinc oxide (ZnO:Al) thin films were directly deposited via plused direct current (DC) magnetron reactive sputtering on glass substrates. High purity metallic Zn-Al (purity: 99.999%, Al 2 wt. %) target and oxygen (purity: 99.999%) were used as source materials. During the reactive sputtering process, the oxygen gas flow rates were controlled by plasma emission monitoring (PEM). The initially as-grown ZnO:Al films at ~280 exhibit rough cone-like surface morphology (RMS~65.6 nm) with high transparencies and excellent electrical properties (~3×10-4 Ωcm). The natively textured surface ZnO:Al thin films were promising TCOs as substrates for PIN-type a-Si thin film solar cells. Large-area (S=30 cm×30 cm) textured AZO coated glass substrates for Si thin film solar cells are obtained via magnetron reactive sputtering technique.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 2802-2806, In this article, we firstly present a study of each layer of the microcrystalline silicon (μc-Si:H ) thin film solar cells prepared in a single chamber by very high frequency-plasma enhanced chemical vapor deposition (VHF-PECVD). The boron-doped microcrystalline silicon (μc-Si:H) films, the intrinsic μc-Si:H films and n-type a-Si films were all deposited at high deposition pressure (1.5 to 2.5Torr). And each layer of the solar cells was deposited at the same electrode distance. The electrical, structural and optical properties of the films were investigated. The dark conductivity as high as 2.75S/cm of ptype μc-Si:H prepared has been achieved at a deposition rate of 1.75Å/s for 25nm thin film. Intrinsic μc-Si:H films with low defect densities were deposited. Through controlling boron and phosphors contamination the single junction μc-Si:H solar cell with 7.62% conversion efficiency (1.0cm2) has been fabricated in a single chamber by VHF-PECVD. Through the optimization of bottom solar cells thickness and application of ZnO/Al back reflector, 10.59% high initial conversion efficiency of micromorph tandem solar cell (1.027cm2) , which bottom solar cell was deposited in a single chamber, with an open circuit voltage of 1.3864V has been fabricated. Micromorph module with 91.5cm2 effective area also shows 9.53% high initial conversion efficiency.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 3232-3234, In this paper, we studied n-SiOx/Al as back reflectors for amorphous silicon (a-Si:H) solar cells. Compared to Al single-layer as back reflectors, adding a n-SiOx layer into the BR could improve the solar cell performance, which not only enhances the short circuit current density by an improvement of spectral response in the wavelength range of 550-750 nm, but also improves the open circuit voltage. On the other hand, the process for depositing n-SiOx films is compatible with a-Si solar cells because the n-SiOx films were also deposited by PECVD method. With an optimized n-SiOx/Al back reflector, a-Si:H solar cells with an intrinsic layer thickness of 270 nm show 13.1% enhancement in efficiency.

Colloque avec actes et comité de lecture. Internationale.; International audience; La maîtrise des propriétés de frottement est une nécessité pour la plupart des systèmes fonctionnels. En effet, même dans les cas où ces systèmes n'ont pas une fonction première de protection mécanique ou de contrôle du contact, les propriétés de frottement vont conditionner facilité de mise en œuvre et durabilité. C'est cette idée que nous illustrerons par différents exemples, empruntés au domaine des matériaux silicatés, pris tant comme vitrages que comme matériaux structuraux. Dans ce domaine, deux échelles apparaissent. A l'échelle atomique, je montrerai comment la friction intrinsèque aux surfaces des verres silicatés peut être contrôlée, parfois subtilement, par la physico-chimie. Comme exemple, je développerai le cas des surfaces dites auto-nettoyantes, mais j'évoquerai également quelques résultats pertinents pour la lubrification de fibres de verre. A une échelle plus macroscopique, c'est l'architecture du système fonctionnalisant qui doit être prise en compte, avec ses propriétés interfaciales aussi bien que mécaniques. J'illustrerai cette idée avec l'exemple des empilements nanométriques de (multi)couches utilisés pour le contrôle thermique. Je montrerai comment leur comportement en rayure est déterminé par leur caractère composite (métal/oxyde), tout en restant d'abord piloté par les propriétés interfaciales (friction et adhésion). Enfin je montrerai comment les techniques récentes de microfabrication, en ajoutant, par la texturation, une dimension supplémentaire aux méthodes de modification de surface, ouvrent un champ d'exploration nouveau pour la fonctionnalisation.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 2623-2626, During the high rate deposition process of hydrogenated microcrystalline silicon(μc-Si:H) thin film in plasma enhanced chemical phase deposition(PECVD), some kinds of heating effects may occur to increase the substrate temperature, arising from the excitation power heat accumulation and the change of the inter-electrode distance or the total gas flow. This paper demonstrates that, though in different ways, all of these heating effects could gradually modify the μc-Si:H structural properties with deposition time, and a higher input power combined with a smaller inter-electrode distance, often used in high rate deposition, could bring a stronger heating effect. Thus we propose both of them should be suitable as much as possible, especially for the device-grade quality μc-Si:H material.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 2631-2633, Hydrogenated microcrystalline silicon (μc-Si:H) solar cells were deposited with very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) process at high deposition rates in a high power and high pressure regime. The structural evolution in μc-Si:H films and solar cells has been investigated. In order to reduce the incubation layer thickness in the initial stage, a high-quality p/i interface layer has been developed by lowering silane concentration and VHF power simultaneously. This interface layer not only acts as a seed layer for the high-rate deposited i-layer, but also it can reduce the ion bombardment on the p/i interface. Then, a novel VHF power profiling technique, which was designed by dynamically decreasing the VHF power step by step during the deposition of μc-Si:H, has been developed to control the structural evolution along the growth direction in the bulk i-layer. Another advantage of this VHF power profiling technique is the reduced ion bombardments on growth surface because of decreasing the VHF power. At last, a high conversion efficiency of 9.36% has been obtained for a single junction μc-Si:H p-i-n solar cell with i-layer deposited at deposition rate over 10 Å/s.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 2627-2630, The deposition of homogenous hydrogenated microcrystalline silicon (μc-Si:H) layers is crucial for the industry production of high efficiency μc-Si:H single junction and a-Si:H/μc-Si:H tandem module. The uniformity of the layers is strongly influenced by the process parameters, e.g. pressure, electrode gap or gas flow rate, but can also be influenced by the hardware configuration of deposition system. The deposition rate uniformity, dark/photo conductivity uniformity, and the effect on the crystallinity distribution of the intrinsic μc-Si:H layer were studied in this paper. After optimizing of the adjusted hardware and the process parameters, a quite uniform distribution of the materials of a-Si:H or μc-Si:H was achieved. Micromorph tandem solar module fabricated on the commercial SnO2 substrate of 0.79m2 area with active aperture conversion efficiency of 8.12% (only Al back reflector) has been obtained and shown in the end

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 2297-2300, We studied the boron contamination at the interface between the p and i layers of μc-Si:H solar cells deposited in a single-chamber PECVD system. The boron depth profile in the i layer was measured by Secondary Ion Mass Spectroscopy. We founded that the mixed-phase μc-Si:H materials with 40% crystalline volume fraction is easy to be affected by the residual boron in the reactor. The experimental results showed that both a 500-nm thick μc-Si:H covering layer and a 30 seconds of hydrogen plasma treatment can effectively reduce the boron contamination at the p/i interface. However, from cost reduction point of view, the hydrogen plasma treatment is desirable for solar cell manufacture because the substrate is not moved during the hydrogen plasma treatment.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 2332-2335, A series of μc-Si:H thin films with high deposition rate were prepared by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) process under high power and high-pressure conditions. Keeping the other parameters constant, the total gas flow rate was adjusted from 100sccm to 500sccm, which led to gradually decreased gas residence time. The influence of total gas flow rate on the deposition process, electrical and micro-structural properties was studied in detail. Plasma emission was recorded by optical emission spectroscopy during μc-Si:H absorber layer deposition at total gas flow rate between 100sccm and 500sccm. The results showed that the photosensitivity (p/d) of μc-Si:H film was maximum and the microstructure factor (R) was minimum when the ratio of H*/H* had a local minimum value at 300sccm. The above results were analyzed using the concept of the gas residence time. It found that device grade microcrystalline silicon materials should be prepared at proper gas residence time.Those μc-Si:H films deposited at different total gas flow rate were applied as the absorber layers in single-junction μc-Si:H solar cells. Conversion efficiency of 8.11% has been obtained at 8.5Å/s with 300sccm total gas flow rate.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 2282-2284, In this paper, the influence of doping ratio and hydrogen dilution on the structural and electrical characteristics of p-μc-SiGe films was investigated in detail. The results shows that, with the increase of doping ratio, the materials transformed from microcrystalline to amorphous, and the dark conductivity changes little first and then decreases steeply. With the increase of hydrogen dilution, the dark conductivity increases first, then decreases. On the contrary, the active energy decreases first, then increases. The growth kinetics of p-μc-SiGe thin films was explored with optical emission spectra (OES) technique. The results shows that, the ration of SiH*/H* decreased with the increase of doping ratio and increased as the hydrogen dilution decreased. So the crystalline volume fraction of thin films decreased. By optimizing the deposition parameters, p-μc-Si1-xGex thin film with high conductivity, low activation energy (0.67S/cm Eg0.042ev) and high crystalline volume fraction of 51% at the thickness of 32nm was achieved.