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32nd European Photovoltaic Solar Energy Conference and Exhibition; 1874-1878, In this paper, several solutions against PID have been tested on mini-modules then 60-cell modules. 4 encapsulants are compared at the mini-module level: two types of ethylene-vinyl acetate (EVA), a thermoplastic polyolefin (TPO) and an ionomer. Then 3 out of 4 encapsulants are compared on 60-cell modules in this study: an ethylene-vinyl acetate (EVA), a thermoplastic polyolefin (TPO) and an ionomer. 3 modules architectures have been also tested: a module with a standard glass and a TPT backsheet, a module with a special thin glass and a TPT backsheet, and a special thin double glass module using the same thin glass (only on 60-cell module). At the end, a module with ion implanted cells, while others components were kept identical, is PID tested. The applied voltage was 1500V in order to prepare the future increase of DC plant voltage. On mini-modules, a first PID test at room temperature (25°C and Al-foil) has been conducted before a more severe test at 70°C (Al foil), allowing us to clearly differentiate the influence of the tested materials on PID degradation of the modules. The conditions of these tests on 60-cell modules were 192 hours 75°C 85RH. Contrary to EVA and standard glass modules, we clearly observed no degradation on thermoplastic polyolefin (TPO), ionomer, thin glass modules and module with ion implanted cells. Using one of these components is a solution against PID.

26 September (2014), 1328 – 1332; International audience; no abstract

L'Al2O3 déposé par ALD est un diélectrique bien connu pour la passivation de surface du silicium type-p. Cependant, une étape de recuit post-dépôt est nécessaire pour activer la passivation. Grâce à des mesures de densités de charges effectives, de défauts d'interface, temps de vie de porteurs de charges, XPS (X-ray Photoelectron Spectroscopy), SIMS (Secondary Ion Mass Spectrometry), sur le même échantillon, une description duprocessus d'activation est donnée. La présence d'hydrogène et d'oxygène est reliée à l'évolution des paramètres électriques pour un recuit de 30min à 450°C pour du silicium type p Cz.

28th European Photovoltaic Solar Energy Conference and Exhibition; 1952-1956, The PROTERRA project develops new processes based on techniques that could be transferred into industrial production of high efficiency and low cost c-Si solar cells and modules. Significant solar cell conversion efficiency improvement and reduction of their production cost are expected using a new cell structure favoring both front and rear passivation associated with self-aligned metallization. To achieve this structure, it is essential to incorporate innovative concepts applicable to most key steps of solar cell manufacturing as selective emitter, rear side passivation by dielectric layers, electrolytic metallization, local BSF and rear contacts. The in-line silicone encapsulation process which reduces the absorption of photons in the UV is used for module preparation with the target to ameliorate module performance. Numerous tests with a wide series of crystalline silicon solar cells have been underway in order to release necessary data for process evaluations. Some interesting experimental results have been obtained in an attempt to identify the best candidates to replace standard processes for c-Si solar cell and module production.

28th European Photovoltaic Solar Energy Conference and Exhibition; 2001-2004, A process for silicon solar cell fabrication associated with self–aligned Ni/Cu metallization is demonstrated with a reduced number of technological steps. After laser ablation of the anti-reflection coating, a nickel seed layer is formed by electroless chemical deposition followed by copper light-induced plating. Laboratory size solar cells were fabricated with different metal finger widths and spacings to evaluate the viability of the process. The best efficiency measured on 4 cm2 multi-crystalline solar cells was of the order of 16.5%. The limiting factors as well as possible improvements of the overall process are discussed.

27th European Photovoltaic Solar Energy Conference and Exhibition; 2063-2067, The goal of Eurogia+ founded LAPSIS project is to develop and apply laser processes in to the production of thin crystalline silicon solar cells based on a passivated emitter and rear locally diffused (PERL) solar cell structure. The complex and expensive steps to form this type of solar cells will be replaced by laser related processes. The overall objective is to offer a complete solution for large volume and low cost production of high efficiency silicon solar cells by combined effect of wafer thickness reduction and solar cell performance improvement. During the first eighteen months of LAPSIS project, several adapted laser irradiation strategies for the realization of advanced front and back side structures of crystalline silicon solar cells were suggested. The innovative processes have been investigated and they are identified as good candidates for replacement of standard process. Short loop solar cells with selective emitter, advanced ECD metallization and boron- BSF are now underway of optimization and evaluation. In parallel we have defined laser system specifications based on industrial requirement and finalized the preparation of a prototype equipment which is ready to perform the tests since the second year of the project. This facilitates the real evaluation of process robustness and production cost. The selected processes will be integrated in a full process flow for high efficiency solar cell production on thin silicon substrates.

27th European Photovoltaic Solar Energy Conference and Exhibition; 1655-1659, The purpose of this work is electrochemical front-side emitter metallization on multi-crystalline silicon (mc-Si) without alignment steps. Selective laser ablation of the silicon nitride (SiNx:H) anti-reflection and passivation coating was performed prior to metallization. The laser used was a frequency tripled Nd:YAG laser with a Gaussian profile, a wavelength of 355 nm and a pulse duration of 10 ns. Selective ablation of SiNx:H was optimized in order to avoid damage to the silicon surface. The optimal laser fluence was of the order of 0.4 J/cm2. An electroless nickel-phosphorous layer (140 - 200 nm) was used as a seed-layer and samples were thermally annealed at 380°C for 2 min to induce silicide formation. The thickening of the Ni contact by Ag has been done by light-induced plating (LIP). Silver thickness was between 5 and 8 μm in order to optimize the fill factor. The best measured efficiency achieved on 200μm thick p-type mc-Si solar cell (area 4.7cm2) was 15.1% with a fill factor of 74.8%. In this case, the Ni seed-layer thickness was 150 nm and the Ag layer was 5.1μm thick. Suns-Voc measurement applied to our cells shows a 15.5% efficiency assuming a FF of 76.7%. The limiting factors, as well as possible improvements using cells with screen printing back-side Al BSF, are discussed.

27th European Photovoltaic Solar Energy Conference and Exhibition; 749-754, The French national BOLID project combines theoretical and experimental studies with the main aims of understanding and suppressing the light-induced degradation related to the formation and activation of the socalled boron-oxygen complexes, which affect the photovoltaic performances of the solar cells prepared from borondoped silicon substrates. In this contribution we introduce the project, review the different methods used and discuss the present status of the project (main results).

26th European Photovoltaic Solar Energy Conference and Exhibition; 853-857, In this work, we present some of the main results obtained within the project “Heterojunction Solar Cells based on a-Si/c-Si” (HETSI) [1], funded by the European Commission in the framework of the 7th Research Framework Program from 2008 to 2011. This project, based on the promising silicon heterojunction technology, represents a concerted effort of the consortium, a well balanced mix of universities, institutes of technology and industrial partners, to combine device modelling, material optimization and characterization, process development (from texturization to metallization), PV cell and module process integration, while cost and environmental issues are addressed as well. Thanks to a better understanding of the device physics from advanced characterization tools and modeling, the results obtained by this consortium have put Europe on the map, with a record cell efficiency of 20,7% on large area n-type c-Si wafers. Moreover, a dedicated module process has been developed with low losses of only 1% absolute from cell to module.

26th European Photovoltaic Solar Energy Conference and Exhibition; 1155-1159, We present an innovative process for n-type silicon solar cells fabrication. Based on the co-diffusion of phosphorus and boron, a plasma enhanced chemical vapor deposition of borosilicate glass (BSG) serves as boron source, whereas POCl3 liquid source is used as phosphorus source. We first study the effect of the BSG deposition parameters on the boron doping results. This reveals that not only the boron precursor (trimethylborate) is important to obtain high doping but also the boron diffusion temperature. We then produce multicrystalline silicon solar cells to study the effect of the boron diffusion temperature and of a low temperature oxidation step introduced after diffusion to remove the boron rich layer. Finally, we demonstrate the feasibility of the co-diffusion for the realization of n-type silicon solar cells.

26th European Photovoltaic Solar Energy Conference and Exhibition; 1285-1288, Selective emitter solar cells can provide a significant increase in conversion efficiency. However most approaches still needs many technological steps and alignment procedures. This paper reports on the comparison of two laser processes for selective emitter. In both cases, the phosphorous glass (PSG) present after the thermal Pdiffusion acts as a dopant source for the laser process. In the first process, the laser-assisted diffusion takes place directly after the thermal diffusion. In the second process, the PSG layer is preserved and covered by silicon nitride. The laser is used to open locally the antireflection and passivation coating, and at the same time, achieve local phosphorus diffusion. This second process is potentially self-aligned if electrochemical front side metallization are used. Numerical simulation of the laser-matter interaction for the two structures is discussed. Preliminary solar cells results for both processes are compared. In particular, illuminated I-V measurements and spectral response measurements are discussed.

26th European Photovoltaic Solar Energy Conference and Exhibition; 2165-2169, This study presents a work about contact optimization for realization of N-Type multicrystalline silicon solar cells. Two packages of pastes from different suppliers were used on two different process sequences. Each package contains an Ag/Al front paste and an Ag paste for back side contacts. Contact formation was made by screen printing. N-type solar cells need boron diffusion to make emitter in front side and phosphorus diffusion to do back surface field. The two diffusions were realized into low pressure furnace (LYDOP®) using BCl3 and POCl3 respectively. At the end of both process sequences, each side is doped with the appropriate type. For each pastes package, we describe electrical illuminated measurements and contact characteristics such as contact resistivity and finger resistance. In a case, low conductivity of aluminum containing front paste was reduced by electrochemical deposition of silver. The effect of plating on series resistance, Fill Factor, and Efficiency is discussed. An Efficiency of 14.40% was obtained.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 2190-2192, In this paper we present a new wet chemical texturing process (Random Honeycomb Texturing) suitable for thin silicon solar cells manufacturing. The benefits of proposed texturing method are: reduced front surface reflectivity; chemical polishing of the rear surface; no defects etch; texturing is independent on saw damage; both sides of the wafer are treated in the same step; relative simplicity of process. The key point of process is the use of blistering of hydrogenated dielectric layer to create the local opening in the etch mask. Texturing process was tested on industrial type high throughput equipment.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 1636-1639, In order to enhance photon transmission into multicrystalline silicon solar cells, double-layer antireflection coatings (ARC) were simulated using the measured optical constants of hydrogenated silicon oxynitride SiOxNy:H and hydrogenated silicon nitride SiNx:H layers deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). On polished surfaces, these optimized structures have the potential to increase the short-circuit current by more than 2% for non-encapsulated cells and up to 0.5% for encapsulated cells, in comparison with the standard single SiNx:H ARC. Industrial multicrystalline silicon solar cells were fabricated in order to validate the simulations. In spite of an inhomogeneous NaOH textured surface, the short-circuit current have shown an increase up to 2.3%, which highlights the potential of such structures for laboratory high-efficiency solar cells.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 1162-1166, The integrated project (IP) Crystal Clear has been finalized in June 2009 and thus a chapter of more than 5 years successful collaboration between European solar cell research institutes and industry is closed. This paper reviews the achievements within the 4th subproject (SP4) of Crystal Clear dealing with the development of advanced solar cell concepts. Within SP4, 12 of the 16 partners have participated and have formed a productive consortium. The goal of this subproject was the further reduction of the cell production costs to enable the psychological important Si PV module price below 1 Euro/Watt. This should be reached by novel cell designs and manufacturing processes in order to achieve a process cost reduction of 40% (cost per Wp). One major effort was put in the development of novel cell concepts and processes suited for thin wafers in industrial fabrication. Three cell concepts were distinguished and developed by the participating institutes: i-PERC, MWT with full Al, and solar cells with laser fired contacts (PERC-LFC). In addition to the effort to implement these concepts into an industrial type of process with large area wafers, excellent results have been achieved on EFG and RGS ribbons. World record results with laboratory-type processes could be reported, with efficiencies of 18.2 % on EFG ribbons and 14.4 % on RGS ribbons. The defect mechanism of these materials has been studied in detail and efficiency limits have been indicated. The paper will refer to the separate contributions submitted to the conference by the different partners on specific topics.

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 1623-1627, In this article, we used 2D simulation to evaluate the influence of the Metal-Insulator-Semiconductor (MIS) and fixed charge density contained in the dielectric layers which may be used for the passivation of the rear side of silicon solar cells. Negative fixed charge densities were found in PECVD SiOx:H and SiNx:H dielectrics by dark-capacitance-voltage measurements, using a new method more adapted to solar cell applications. Next, multicrystalline silicon solar cells based on the i-PERC process were made with PECVD SiOx:H / SiNx:H stacks of different thicknesses. I-V characterization showed open-circuit voltage and fill factor degradations for the processed cells compared to the reference. These degradations were analyzed by spectral response measurements, scanning electron microscopy and infrared thermography. It was found that the serigraphy paste and the laser impacts on grain boundaries were responsible for the degradations.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 1816-1819, This paper is focused on some specific problems relayed with application of high sheet resistance emitters in industrial solar cells and modules. The behaviour of such emitters is studied from the phosphorous diffusion step up to the encapsulated cells with different surface treatments. For the emitter formation the LYDOP technique was used. Two ways leading to increase of emitter sheet resistance were tested: reduced diffusion temperature and shorted diffusion time. The obtained emitter profiles were analysed using SIMS technique. Both types of emitters were tested at cell level. The impact of encapsulation was studied for high and low resistivity emitter cells. The greater current increase due to encapsulation was observed for low resistivity emitters.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 1182-1187, Determination of solar cell parameters by illuminated IV measurement is a standard characterisation technique used by many partners active in photovoltaics. The aim of this work is to carry out a cross check of different measurement set-ups used by different research partners of the EU CrystalClear project using industrialtype multicrystalline Si solar cells. In a first round robin a significant spread of all cell parameters (Voc, jsc, FF and efficiency) could be observed. After distribution of sister cells to selected cells calibrated at ISE CalLab, a second round robin was carried out. The spread in FF and jsc could be significantly reduced. Repeatability tests showed that by using a photo diode fluctuations of light intensity can be minimised and variations in jsc can be decreased down to 0.2 mA/cm2. Remaining systematic errors are control of cell temperature, contacting geometry, and use of appropriate reference cells.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 1793-1796, We propose to study the emitter formation using Lydop technology, which is low pressure phosphorus diffusion. Various emitters are obtained by varying diffusion parameters, i.e., temperature, drive in time, POCl3/O2 ratio and preoxidation time. This allows to observe the evolution of the emitter dead layer as a function of diffusion parameters and to conclude on the emitter quality. c-Si and mc-Si are then elaborated for different kinds of emitter. POCl3/O2 ratio and preoxidation time are of particularly interest for enhancing emitter performances. While POCl3/O2 ratio decrease enhances the emitter performance, it leads to a series resistance increase. Preoxidation, consisting in the formation of a thermal oxide prior to diffusion, leads to a Joe enhancement, and a 1% absolute increasing of efficiency.

29th European Photovoltaic Solar Energy Conference and Exhibition; 1328-1332, New advanced processes have been developed in the frame of the French National PROTERRA Project based on techniques that could be transferred into industrial production of high efficiency and low cost c-Si solar cells and modules. Significant solar cell conversion efficiency improvement was expected using a new cell architecture based on PERC concept (Passivated Emitter and Rear Cell) favoring both front and rear surface passivation. To perform this structure, it is essential to integrate innovative concepts developed on technology platforms of research partners to principal steps of industrial solar cell manufacturing at EDF ENR PWT as selective or homogeneous high-sheet-resistance emitter, advanced front side metallization, rear surface passivation by dielectric, localized BSF and localized back contact. The passivation effects of the dielectric layers were studied in the function of their physicochemical properties and applied thermal treatments. The comparison of different laser sources allowed defining the optimum conditions for the ablation of dielectric layers while limiting induced damages in the underlying silicon substrate. Different aluminum screen printing pastes were also evaluated using different contact configurations for their ability to form an effective localized BSF and a good rear side contact while preserving the high quality of passivation in non-ablated regions. The different methods used to form the front contact as screen printing and electrochemical deposition were evaluated. The implementation of selected technological bricks in a complete manufacturing process of solar cells on p-type crystalline silicon substrates of industrial size 156mm x 156mm yielded a high average conversion efficiency of 19.5 % demonstrating an absolute gain of +0.8 % compared to standard full area Al-BSF process.