Sunways AG

Konstanz, Germany

Sunways AG

Konstanz, Germany
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Muller J.,Institute for Solar Energy Research Hamelin | Bothe K.,Institute for Solar Energy Research Hamelin | Gatz S.,Institute for Solar Energy Research Hamelin | Plagwitz H.,Sunways AG | And 2 more authors.
IEEE Transactions on Electron Devices | Year: 2011

We study recombination properties and the formation of base contacts, which are realized by local laser ablation of a dielectric stack and the subsequent full-area screen printing of an Al paste. Based on charge-carrier lifetime measurements using the camera-based calibration-free dynamic infrared lifetime mapping technique, we determine contact reverse saturation current densities as low as J0, cont = 9 × 102 fA/cm2 on 1.5-Ωcm p-type float-zone silicon (FZ-Si) and J0, cont = 2 × 104fA/cm2 on 200-Ωcm p-type FZ-Si. Scanning electron microscopy images reveal that the thickness of the highly Al-doped (Al-p+) layer considerably depends on the contact size and the contact layout (e.g., point or line contacts). Based on this finding, we show that Al-p+ layer thickness WAl-p+ significantly affects the contact recombination. As a result, we show which local contact geometry is most appropriate for the lowest contact recombination employing local Al-alloyed contacts. © 2011 IEEE.

Urrejola E.,ISC Konstanz | Peter K.,Sunways AG | Plagwitz H.,Sunways AG | Schubert G.,Sunways AG
Applied Physics Letters | Year: 2011

We show that the lateral spread of silicon in a screen-printed aluminum layer increases by (1.50±0.06) μm/°C, when increasing the peak firing temperature within an industrially applicable range. In this way, the maximum spread limit of diffused silicon in aluminum is predictable and does not depend on the contact area size but on the firing temperature. Therefore, the geometry of the rear side pattern can influence not only series resistance losses within the solar cell but the process of contact formation itself. In addition, too fast cooling lead to Kirkendall void formations instead of an eutectic layer. © 2011 American Institute of Physics.

Cabrera E.,International Solar Energy Research Center Konstanz | Olibet S.,International Solar Energy Research Center Konstanz | Rudolph D.,International Solar Energy Research Center Konstanz | Wefringhaus E.,International Solar Energy Research Center Konstanz | And 3 more authors.
IEEE Journal of Photovoltaics | Year: 2013

For screen-printed Ag-paste metallization, the growth of Ag crystallites into Si is essential for the current conduction from the Si emitter to the silver finger. There are strong indications that for low contact resistances, some of these Ag crystallites need to be in direct contact with the silver finger without a separating glass layer in between. In this paper, we concentrate on the origin of Ag crystallites grown into Si in direct contact with the silver finger. On textured surfaces, we vary the Si pyramid sizes, round the pyramid tips to varying degrees, and fabricate flat smooth surfaces. We observe that the size of the pyramids does not play an important role in the achievement of low specific contact resistivity unless the pyramid heights become smaller than the thickness of the glass layer, but rounding of the pyramid tips with standard heights increases specific contact resistivity significantly. From our microscopic investigations, we conclude that the largest influence on the topography-dependent contact resistance comes from the glass coverage governing the amount of Ag crystallites directly connected with the silver finger bulk. Furthermore, Ag crystallites in direct contact with the silver finger are also observed on c-Si without n$+ emitter doping. © 2011-2012 IEEE.

Book F.,University of Konstanz | Wiedenmann T.,University of Konstanz | Schubert G.,Sunways AG | Plagwitz H.,Sunways AG | Hahn G.,University of Konstanz
Energy Procedia | Year: 2011

Efficiencies of large area n-type silicon solar cells with a screen printed rear side aluminum-alloyed emitter are mainly limited by their front surface recombination velocity. The front surface therefore has to be passivated by an effective passivation layer combined with a front surface field (FSF). In this work we investigate the influence of the front surface passivation quality and the base resistivity for a selective FSF n-type solar cell. The potential of this solar cell concept is assessed by PC1D simulations and QSSPC measurements. Furthermore we present solar cell results of all screen printed large area n-type Cz-Si solar cells with an aluminum rear emitter and a selective etch-back FSF passivated by a PECVD-SiN x or a SiO 2/SiN x stack. The applied processing sequence is based on industrially available processing equipment and results in an independently confirmed cell efficiency of 19.4 % on a 6" solar cell. © 2010 Published by Elsevier Ltd.

Cabrera E.,International Solar Energy Research Center | Olibet S.,International Solar Energy Research Center | Glatz-Reichenbach J.,International Solar Energy Research Center | Kopecek R.,International Solar Energy Research Center | And 2 more authors.
Energy Procedia | Year: 2011

Good progress in the front silver metallization paste development has lead to significant efficiency improvements for standard crystalline silicon solar cells in the past years. In order to gain more insight into the contact mechanism, recent silver pastes capable of contacting higher resistive emitters - without selective emitter and without subsequent plating - were studied in this work. Within solar cell silver thick film contact investigations, two different theories predominate to explain the current transport from the silicon into the silver finger's bulk. The first one establishes that the current mainly flows through the Ag-crystallites grown into the silicon emitter that are either directly connected to the silver bulk or separated from the silver finger by a thin glass layer. The second one suggests that at optimum firing conditions nano-Ag-colloids are formed inside the glass layer allowing the current to flow into the silver finger through multi-step tunnelling. By sequential selective silver and glass etch-back and reconnection via liquid conductive silver, different combinations of conductivity path systems were investigated. On pyramidal textured Si, contacts from recent silver pastes reveal Ag-crystallites at the pyramid tops which are likely directly connected to the body of the Ag-finger. Even on flat Si we observe these likely direct contacts with advanced silver pastes. Our liquid conductive silver experiments indicate that the largest current contribution is flowing through these Ag-crystallites. © 2010 Published by Elsevier Ltd.

Urrejola E.,International Solar Energy Research Center | Peter K.,International Solar Energy Research Center | Plagwitz H.,Sunways AG | Schubert G.,Sunways AG
Energy Procedia | Year: 2011

Solar cell concepts with passivated, locally contacted rear side have gained much interest over the last years due to the development of advanced passivation techniques. However, there are still open questions regarding the understanding of the local Al-Si contact formation and its influence on the local back-surface-field formation for industrial screen-printed aluminum pastes. In this work we show that the geometry of the rear pattern (contact size and contact spacing) strongly influences the Al-Si interaction in the local contact openings: Si diffuses in Al through narrow dielectric barrier openings and spreads laterally to a determined limit determined by the firing temperature. We found that the contact spacing can affect the tendency for formation of Kirkendall voids below the Al-Si contacts instead of an eutectic layer. When decreasing the contact spacing and therefore the overlap of Al on each side of the local opening, the melt saturates faster and the formation of a deep (high-quality) local back-surface-field is increased. This may minimize the presence of voids. This physical observation helps on the design of the rear pattern for rear passivated solar cells and gives further understanding of the Al-Si interaction during the firing process. © 2011 Published by Elsevier Ltd.

Beaucarne G.,Dow Corning | Schubert G.,Sunways AG | Hoornstra J.,Energy Research Center of the Netherlands | Horzel J.,IMEC | Glunz S.W.,Fraunhofer Institute for Solar Energy Systems
Energy Procedia | Year: 2011

The Third Workshop on Metallization for Crystalline Silicon Solar Cells was held in Charleroi, Belgium on 25 and 26 October 2011. This paper reports on the different contributions and discussions that took place. Great progress has recently been achieved in paste development, which yet again has stretched the lifetime of screen-printed metallization technology. Nevertheless, a transition towards Cu plating-based metallization is anticipated, and solutions to the different challenges were presented and discussed. © 2012 Published by Elsevier Ltd.

The present invention relates to a circuit arrangement for electrical installations for converting and adapting a DC voltage of a voltage source, more particularly for a solar inverter of a photovoltaic installation, having an electrical output, which can be coupled to an inverter, wherein, at the electrical output, a potential in a positive branch of an intermediate circuit of the electrical installation can be increased in such a way that an output potential of a negative pole of the voltage source assumes a value greater than the potential of the negative pole before the increase, or the potential in a negative branch of the intermediate circuit of the electrical installation can be reduced in such a way that an output potential of a positive pole of the voltage source assumes a value lower than the potential of the positive pole before the reduction, and having a compensation device designed for compensating for the electrical power between the positive branch of the intermediate circuit of the electrical installation and the negative branch of the intermediate circuit of the electrical installation during the operation of the circuit arrangement. The present invention furthermore relates to a method and a photovoltaic installation.

Sunways AG | Date: 2012-01-13

The invention relates to a current measuring device for detecting a current flowing through a power line, said device comprising: a magnetic loop for receiving the power line; an excitation device designed to magnetise the magnetic loop by means of a periodic signal; a first current sensor designed to detect an exciting current flowing in the excitation device on the basis of the periodic signal and/or the current to be detected; and a determination device that determines a shift of the detected exciting current on the current axis, said shift being caused by the current, and, as a result, deduces the intensity of the current to be detected. The invention also relates to a solar inverter and to a method for detecting a current.

Sunways AG | Date: 2012-10-16

Solar cells; photovoltaic installations and systems consisting of photovoltaic cells, photovoltaic solar modules, photovoltaic roofing members, photovoltaic cladding panels, and photovoltaic solar hybrid modules all for the purpose of converting electromagnetic radiation to electrical energy and components and spare parts for photovoltaic installations and systems therefor; photovoltaic inverters; electronic components for storing electric energy and/or for converting electric energy as received by solar cells, photovoltaic solar modules into other forms of electric energy; solar batteries. Non-metallic building materials, namely roof and facade parts made of glass, photovoltaic elements or other materials. Installation, maintenance and repair of photovoltaic installations and systems.

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