P. Fath

RENA GmbH, Berg am See, Bavaria, Germany

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Publications (115)138.98 Total impact

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    ABSTRACT: The global PV module production capacity in 2014 is assumed to be about 60 GW with 90% based on c-Si and 10 % on thin film technology. Since the demand of module is expected to be about 50 GW in 2014 there are some challenges and opportunities of modern PV manufacturing. The key is the implementation of innovative technologies into existing production environment and still meeting the challenging production cost requirements despite that prices have been stabilizing since summer 2013. Presently numerous manufacturers announced the implementation of differing solar cell concepts, based on an evolutionary improvement of the standard cell type, aiming towards higher efficiencies in mass production. This trend, resulting in an increasing diversification, also creates new demands with regard to the manufacturing equipment, which have to be met by the equipment manufacturers. The implementation of new techniques and new equipment aims at lower production costs per Wp due to increased efficiency. On the other hand the obtained efficiency gain only results in a quite limited window for increased processing costs or invest in new equipment.
    Photovoltaic Specialist Conference (PVSC), 2014 IEEE 40th, Denver, CO; 06/2014
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    ABSTRACT: In this paper, we present the InPERC technology implemented into a multicrystalline silicon (mc-Si) solar cell production of a major Chinese cell manufacturer. Stable average efficiencies over 18% were demonstrated. Best average efficiencies of 18.4% were achieved on mc-Si solar cells without selective emitter with a best cell efficiency of 18.8%. To reduce the cost of ownership (CoO) of the InPERC upgrade, the annealing step after ALD of Al 2 O 3 was successfully skipped by integrating it into the direct tube PECVD without increase of PECVD process time. Furthermore, the Al 2 O 3 thickness was reduced to 4 nm and the etch removal for rear side smoothening to 2 µm without loss in efficiency. An InPERC module was subjected to accelerated ageing tests with stable results. In a CoO-comparison of different PERC routes, the InPERC technology showed the lowest total CoO and the lowest payback period of all investigated PERC candidates.
    SNEC 2014 - The 8th International Photovoltaic Power Generation Conference & Exhibition; 05/2014
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    ABSTRACT: In this paper, we present results of the implementation of the RCT Solutions* Multi PERCT technology into an industrial pilot production of a Chinese cell manufacturer. This technology upgrade is an alternative to boost existing multi crystalline solar cell production above 18% based on standard mass production equipment and standard quality wafers. The process sequence utilizes mass production equipment used for manufacturing standard screen printed full area Al-BSF solar cells. In addition, the rear side is passivated using standard PECVD equipment and prior to this step it has been totally diffused (PERCT) with a cost effective boron diffusion using BBr3 utilizing an upgraded standard diffusion tool. Furthermore, a laser is used to open the rear side contacts prior to screen printing of the metallization. RCT’s Multi PERCT technology upgrade was transferred to an industrial pilot production of a Chinese cell manufacturer. On standard multi crystalline wafer material efficiency gains of about 0.6%abs were demonstrated. Top average efficiencies of 18.44% could already be achieved up to now without front side optimization. A unique feature of this technology is the manufacturing of the world’s first bifacial multi crystalline solar cell with cost effective aluminum grid printed metallization on the rear side instead of expensive silver fingers.
    SNEC 2014 - The 8th International Photovoltaic Power Generation Conference & Exhibition, Shanghai; 05/2014
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    ABSTRACT: For an improved solar cell performance rear side passivation and local contacts in combination with a laser diffused selective emitter were developed and cell efficiencies up to 19.5% were reached. Several fundamental physical impacts of major importance, such as the light trapping behaviour because of specific surface preparations, the resulting passivation performance, the interaction of emitter and rear surface recombination currents, were investi-gated. In the first test runs in a production environment average solar cell efficiencies of 18.6% and best cell efficiencies of 19.0% were successfully achieved under non-adapted production conditions.
    Energy Procedia 12/2012; 15:1–9. DOI:10.1016/j.egypro.2012.02.001
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    ABSTRACT: Currently leading crystalline solar cell technologies comprehend rear side passivation with local aluminium back surface field and dielectric reflection layer. For this purpose Centrotherm developed the centaurus technology, which is based on a rear side dielectric passivation and local aluminium BSF (LBSF) in combination with a laser diffused selective front side emitter. A major aspect of the developed technology is its compatibility for an upgrade of existing Al-BSF cell production lines and for turnkey lines as well. Moreover, the equipment required for the new technology is merely based on familiar technologies like wet etching, PECVD layer deposition, laser processing and screen printing. This conformity with common technologies and the simplicity and sustainability of their production implementation as well as the exceptional high cell efficiencies in production favour the new centaurus technology. In production average cell efficiencies well over 19 % have been achieved and best cell efficiencies of 19.6 % were reached. Under laboratory conditions average cell efficiencies of module ready centaurus solar cells with rear side Ag pads reached 19.7 %, with best cell efficiencies up to 19.9 %. These results clearly indicate that the centaurus technology is approaching module ready solar cell efficiencies of 20 %. Assembled modules demonstrate the excellent power conversion of the centaurus solar cells. First environmental tests have been successfully passed. (C) 2012 Published by Elsevier Ltd. Selection and peer-review under responsibility of the scientific committee of the SiliconPV 2012 conference.
    2nd International Conference on Crystalline Silicon Photovoltaics; 01/2012
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    ABSTRACT: With the objective of high efficiency solar cells rear side passivation with local aluminium back surface field and dielectric reflection (Al-LBSFR) were developed at Centrotherm and cell efficiencies of 19.4% were achieved. In this paper major physical properties of the developed technology, named centaurus technology, are presented.A low reflection on the solar cell front side is achieved by a textured surface, which enables in particular an inclined light entry at the solar cell front side, which is mandatory for a total light reflection on the solar cell dielectric rear side. Likewise a smooth instead of a textured rear side surface was more suitable for a high rear reflection and also more appropriate for better rear surface passivation. In addition, the influence of the rear side local BSF and metallization fraction was identified as a possible Voc limitation in combination with the front emitter saturation currents. Lower temperature coefficients of the cell power output or cell efficiency and of the open circuit voltage were evaluated for Al-LBSFR cells.
    Energy Procedia 12/2011; 8:415-420. DOI:10.1016/j.egypro.2011.06.159
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    ABSTRACT: This second edition of the Strategic Research Agenda (SRA) was prepared by the Science, Technology and Applications Group of the EU Photovoltaic Technology Platform based on consultations with representatives of research, industry and other stakeholders. The members of the Working Group are experts in photovoltaic (PV) technology, working as senior researchers in the public and private sectors. Although the group has attempted to cover all the most important parts of PV science, technology and applications and to address all the most important research topics, the reader may find some aspects insufficiently treated. Comments are, therefore, welcome through the PV Technology Platform secretariat (see www.eupvplatform.org). The SRA will be updated as required in order to reflect developments in the photovoltaic solar energy sector.
    2nd edited by Nicola Pearsall, Arnulf Jäger-Waldau, 09/2011; Publications Office of the European Union., ISBN: 978-92-79-20172-1
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    ABSTRACT: A record independently confirmed production cell efficiency of 19.3% is presented for a large area P-type CZ silicon solar cell, based on the UNSW laser doped selective emitter technology. In this work, the innovative and patented laser doping technology is simply added to a standard Centrotherm turnkey line, operating with a modified process and the addition of the laser doping and light induced plating steps. Impressively, this record efficiency is achieved by using standard commercial grade p-type CZ grown silicon wafers on standard production equipment and exceeds the previous independently confirmed record for any technology of 19.2% using a standard aluminium back surface field with full rear coverage. The avoidance of laser induced defects is discussed in this work, to overcome previous limitations of the laser doping technology using conventional Q-switched lasers or the laser chemical processing method. It is demonstrated that the use of appropriate lasers can avoid thermal cycling whilst still allowing for the sufficient mixing of dopants, and allow laser doping to be performed through a standard SiN layer with contacts formed through a self-aligning metallisation scheme.
    IEEE Journal of Photovoltaics 07/2011; 1(1):000047-000047. DOI:10.1109/PVSC.2011.6185842 · 3.00 Impact Factor
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    ABSTRACT: The European Photovoltaic Technology Platform published its Strategic Research Agenda for Photovoltaic Solar Energy Technology (SRA) in 2007. It describes what R&D work the EU and its Member States should fund to make PV a very widely used technology generating significant economic returns for Europe. This Implementation Plan follows on from the SRA, describing how to put into practice the SRA’s findings and recommendations. Like the SRA, the Implementation Plan has been developed to serve as a reference document for individuals and organisations involved in PV R&D. The contents of this Plan reflect the outcome of detailed discussions and analyses by the members of the Working Group on Science, Technology & Applications of the Platform, as well as the feedback received in a public consultation. Both documents are available on the Platform’s website, www.eupvplatform.org. The page where an electronic version of this document, and links to supporting information, can be found is www.eupvplatform.org/documents/ip.html.
    08/2009; Office for the Official Publications of the European Union., ISBN: 978-92-79-12391-7
  • P. Fath · S. Keller · P. Winter · W. Jooss · W. Herbst
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    ABSTRACT: This paper reports on the status and perspective of crystalline silicon (c-Si) solar cell production from the viewpoint of a turnkey production line and technology supplier. It exemplifies selected results of centrotherm's strategic research and roadmapping process. The paper addresses the question of cost, timeframe and risk in transferring new technologies from lab level to mass production targeting at the ultimate ambition in PV: Grid parity.
    Photovoltaic Specialists Conference (PVSC), 2009 34th IEEE; 07/2009
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    ABSTRACT: This paper reports on the development of a masked process for the production of buried contact solar cells on multi-crystalline silicon. The process results in high efficiencies, and only includes steps that would be feasible in an industrial environment. We report here on different mask candidates and on the importance of hydrogenation with the new process. Using the developed process, we produced 111 large area (12 × 12 cm2) cells and achieved an average cell efficiency of 16·2%. The best cell had an efficiency of 16·9%, a Voc of 616 mV, a Jsc of 35·0 mA/cm2 and a fill factor of 78·3%. Copyright © 2008 John Wiley & Sons, Ltd.
    Progress in Photovoltaics Research and Applications 09/2008; 16(6):467 - 477. DOI:10.1002/pip.827 · 9.70 Impact Factor
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  • Gunnar Schubert · Frank Huster · Peter Fath
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    ABSTRACT: Existing models of the silver thick-film contact to an emitter are summarised and recent developments focusing on contact formation and current transport mechanisms are presented. As a glass layer exists at the silicon-thick-film interface the current transport mechanisms are not obvious. The main hypotheses are: current transport via spike-like direct silver–silicon interconnections or via tunnelling through the chemically modified glass layer. Recent investigations showed that silver crystallites grow into the emitter from the glass frit containing dissolved silver [G. Schubert, B. Fischer, P. Fath, in: Proceedings of photovoltaics PV in Europe Conference, Rome, 2002, pp. 343–346 [1]]. These silver islands are covered by a thin glass layer [C. Ballif, D.M. Huljic, A. Hessler-Wyser, G. Willeke, in: Proceedings of the 29th IEEE PVSC, Glasgow, 2002, pp. 360–363 [2]]. Further investigations are necessary to study the crystallite-growth mechanism as well as the current-transport mechanism from the crystallites to the finger.
    Solar Energy Materials and Solar Cells 11/2006; 90(18-19-90):3399-3406. DOI:10.1016/j.solmat.2006.03.040 · 5.34 Impact Factor
  • Holger Knauss · Barbara Terheiden · Peter Fath
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    ABSTRACT: In this publication we present a realisation of a large-area metallisation wrap through (MWT) back-contact-solar cell with electroless-plated contacts. The MWT cell is a very promising back-contact solar-cell concept since the additional effort required to process MWT instead of conventional cells is limited to the formation of a small number of holes. In addition, the concept can easily be applied to very large area cells.We introduce a 9.8cm×9.8cm MWT solar cell, which reaches an efficiency of 16.1%. Up to this point cell performance is limited by local shunting, which results from non-optimal nickel sintering.
    Solar Energy Materials and Solar Cells 11/2006; 90(18):3232-3237. DOI:10.1016/j.solmat.2006.06.047 · 5.34 Impact Factor
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    ABSTRACT: In this paper we present n-type Si solar cells on large area mc-Si wafers with a boron diffused emitter at the front side. The focus of our studies is mainly related to the front surface of the solar cell. We have optimised BBr<sub>3</sub>-diffusion and in-situ oxidation with respect to the homogeneity of the sheet resistance and substrate degradation. After diffusion even a slight improvement of the minority charge carrier lifetime was measured, which can be related to B-gettering. The emitter is contacted by AgAl-paste and passivated by thermal SiO<sub>2</sub>. The development and optimisation of all processes led to solar cells with efficiencies of 14.7% on mc-Si and 17.1% on Cz-Si substrates. In addition to this we present an innovative interconnection of modules using our developed cell (patent pending). We show an alternate serial interconnection of p- and n-type solar cells resulting in easier module processing
    Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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    A. Kranzl · R. Kopecek · K. Peter · P. Fath
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    ABSTRACT: The standard industrial multi-crystalline silicon (mc-Si) solar cell is monofacial and includes screen printed aluminum back surface field (BSF). A simple approach to increase performance and reduce costs per W<sub>peak</sub> is to collect the albedo on the rear side. In this work a bifacial, screen printed mc-Si solar cell with boron BSF is demonstrated. Rear to front efficiency ratios of up to 0.83 have been reached on 100times100mm<sup>2</sup> mc-Si wafers with a thickness of about 200mum. The best solar cell processed so far with a boron BSF had an efficiency under front side illumination of eta=16.1% and a back to front efficiency ratio of 0.77. The possible gain in performance in later operation was estimated using PC1D simulation and depends on the albedo that is the amount of light that penetrates into the solar cell from the rear side. The simulation was confirmed by outside module tests, leading to an average gain of 19.5% over one day
    Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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    ABSTRACT: Multi-crystalline silicon has dominated the photovoltaic market in recent years and with advances in isotexturing and the production of increasingly thinner and larger wafers it is set to play a significant role in the future. As with other cell types, laboratory efficiencies remain higher than those achieved in production. Previous large area efficiency records on multi-crystalline silicon have included a 17.6% efficient cell produced at the University of Konstanz and a 17.7% efficient cell produced by Kyocera. The 17.6% cell was made using the buried contact technique. Again using this technique and multi-crystalline silicon, we have made an 18.1% efficient cell, independently confirmed by the calibration laboratories at Fraunhofer ISE. The area of the cell is 137.7 cm<sup>2</sup>; V<sub>oc</sub> is 636 mV and J<sub>sc</sub> is 36.9 mA/cm<sup>2</sup>. To the best of our knowledge, this is a new world record
    Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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    ABSTRACT: We present bifacial solar cells processed with a sequence suitable for industrial production. This method uses the LPCVD silicon nitride deposition based on DCS (dichlorosilane) or BTBAS (bis-(tertiary butyl amino)-silane). The bifacial solar cell process on wafers of 200 mum thickness has the following steps: (1) boron doped BSF of R<sub>sheet </sub>=60 ohm/sq; (2) POCl<sub>3</sub> emitter (on front side) of R<sub>sheet</sub>= 50-55 ohm/sq; (3) thermal oxidation of the wafer surfaces; (4) the deposition of DCS or BTBAS based LPCVD silicon nitride on either sides of the wafer (5); finger grid printing on both sides and firing; (6) edge isolation. The solar cells produced with the DCS based silicon nitride process exhibit fill factor (FF) values of 76% on p-type and 75% on n-type solar cells with a rear to front efficiency ratio eta<sub>rear</sub>/eta<sub>front</sub> of 67% for the p-type solar cells and 43% for the n-type solar cells. The solar cells with the BTBAS silicon nitride show FF values close to 72% and eta<sub>rear</sub>/eta<sub>front</sub> 68% for p-type solar cells
    Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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    ABSTRACT: We present low cost, screen printed industrial solar cells with a rear Al-emitter for n-type mono- and mc-Si large area thin wafers showing efficiencies of 16.4% and 14.4% respectively. The gap of 2% absolute between the cell efficiencies for mono- and mc-Si is not material related but is largely due to the non-textured surface of the mc-Si substrate. Applying a surface texture by acidic wet chemical etching could lead to efficiencies above 15% on the mc-Si material. The process is based on the standard industrial p-type firing through solar cell concept with slight modifications in individual processing steps similar to the Phostop cell presented by Ebara Solar. There is still need for further optimisation before industrialisation for instance in the fields of wafer bowing reduction and the implementation of AgAl pads for wafer interconnection. We propose two different ways of pad printing-one directly to the Al-emitter, the other on top of the Al rear contact
    Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on; 06/2006
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    ABSTRACT: Record cell efficiencies were achieved with newly developed processes. An integral approach from wafer to module was used. Starting with high-purity feedstock, high-quality large-area mc-Si wafers were made and characterized. Initial lifetimes of up to 160 µs were observed. Three cell concepts were developed further to obtain high efficiency cells: 1) based on screen-printing and complete inline processing; 2) based on V-grooved texturing and roller printing; 3) based on a hybrid buried contact concept with screen-printed Al BSF. With advanced inline processing an independently confirmed efficiency of 17.0% was achieved on 156 cm 2 mc-Si, which is a record for complete inline processing. A full size module made of cells processed with this process has a peak power of 94.3Wp, which corresponds to an encapsulated cell efficiency of 16.8%. Roller printing on V-grooved cells resulted in an independently confirmed efficiency of 17.2%. With the hybrid buried contact concept an efficiency, again independently confirmed, of 18.1% was reached on a cell area of 137 cm 2 ; a record for this size. This record cell was used to determine a roadmap towards 20% mc-Si cell efficiency. For that, it is mainly needed to improve the rear side passivation and rear side internal reflection. This can be done with a di-electric layer for passivation and local contacts. Furthermore, the shading losses should be reduced with for example the Angled Buried Contact concept.

Publication Stats

729 Citations
138.98 Total Impact Points

Institutions

  • 2014
    • RENA GmbH
      Berg am See, Bavaria, Germany
  • 1994–2008
    • Universität Konstanz
      • Department of Physics
      Konstanz, Baden-Wuerttemberg, Germany