A. Grohe

SdPhotonics (United States)

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R. Preu

Fraunhofer Institute for Solar Energy Systems

Stefan W. Glunz

Fraunhofer Institute for Solar Energy Systems

G. Willeke

Fraunhofer Institute for Solar Energy Systems

Haro Fritsche

Technische Universität Berlin

E. Schneiderlöchner

Von Ardenne (Germany)

D. Bíro

University of Freiburg

Wolfgang Gries

VPIphotonics (Germany)

H.‐J. Krokoszinski

Robert Bosch (Germany)

C. Schöllhorn

Robert Bosch (Germany)

Jan Nekarda

Fraunhofer Institute for Solar Energy Systems

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Fraunhofer Institute for Solar Energy Systems

Fraunhofer Society

Robert Bosch (Germany)

Institut für Solarenergieforschung

Leibniz University Hannover

University of Freiburg

Friedrich-Alexander-Universität Erlangen-Nürnberg

Australian National University

Forschungszentrum Jülich

Technische Universität Berlin

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Einsatz von Laserverfahren zur Prozessierung von kristallinen Silizium-Solarzellen

A. Grohe

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Citations (4)

LFC ON SCREEN PRINTED ALUMINIUM REAR SIDE METALLIZATION

World Conference on Photovoltaic Energy Conversion (2009)

R. Preu D. Bíro A. Grohe M. Hoerteis L. Gautero

In this paper we report about first results regarding laser fired contacts (LFC) on an optimized screen printed aluminum rear side layer and compare it with our standard LFC procedure on evaporated aluminum layers. First of all, the influence of the laser pulse energy, pulse duration and amount of pulses on the resistance of one contact is evaluated. Since this value depends strongly on the size of the contact also the recombination losses in the contact area have to be considered in order to compare and qualify LFC contacts comprehensively. We have achieved cell efficiencies > 18.0 % on industrial like processed wafers, which underlines the potential of this approach. Finally, a 20.5 % efficiency solar cell with an aerosol printed front metallization manufactured on laboratory scale is presented, which is the best value ever reported for solar cells with fired front and back side metallization.

Contact resistance

Equivalent series resistance

Pulse duration

10.4229/24theupvsec2009-2cv.2.10

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Detailed analysis of annealing silver front side contacts on silicon solar cells

Stefan Kontermann A. Grohe R. Preu

New concepts for high efficient solar cells require a post processing annealing step for passivation quality improvement. For cutting costs, thick film metallization is used for the front side. In this paper annealing steps of different duration and temperature are applied to standard industrial silicon solar cells to probe the sensitivity for such a front side metallization towards annealing. This paper focuses on five minute annealing under nitrogen atmosphere and determines favourable annealing temperatures and metallization pastes. In our investigations I–V curve measurements showed that from a certain threshold onwards, an increasing thermal budget decreases cell's performance. Series and contact resistance measurements were determined to be significantly affected by annealing. Scanning electron microscopy (SEM) revealed that silver crystallites at the silver silicon interface are transformed in shape for annealing at high temperatures which is most probable the microscopic reason for an increased contact resistance.

Polycrystalline silicon

Passivation

Equivalent series resistance

Contact resistance

10.1109/pvsc.2008.4922788

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Experimental and Numerical Investigations of Laser Beam Welding with an Ultra-high Brightness Direct-diode Laser

Physics Procedia (2016)

Artur Laukart Stefanie Kohl Haro Fritsche A. Grohe Bastian Kruschke

Laser beam welding of steel sheets with conventional disc and fibre lasers is part of many manufacturing processes, e.g. car manufacturing. In modern times, all manufacturing processes are also evaluated regarding sustainability. Although conventional beam sources have an ever increasing efficiency, direct-diode lasers are said to make a step in the wall-plug efficiency in comparison to conventional beam sources due to a missing brightness-converter. Investigations concerning laser beam welding with ultra-high brightness direct-diode lasers were carried out, showing heat conduction welding as well as deep penetration welding of 22MnB5 steel sheets is possible. Furthermore a beam parameter product of about 8 mm-mrad was measured, showing comparable beam quality to conventional disc and fibre lasers. Metallographic cuts were used for determining the welding penetration depth and cross-section. Especially the cross-sections, as a measure for process efficiency, show almost the same result using a direct-diode laser or a disc laser. Due to the limited laser power of 500W, numerical simulations were used to extend the experimental results.

10.1016/j.phpro.2016.08.146

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Multi-wavelength resonant pumping of Er:YAG lasers for energy efficient trace gas detection systems

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2015)

Haro Fritsche Oliver Lux Casey Schuett M. Gaertner Ronny Juhre

The multiplicity of narrow absorption lines of erbium ions in the spectral range from 1450 to 1540 nm is exploited for the development of a highly efficient Er:YAG laser emitting at 1645 nm. Resonant pumping of the active medium with an absorption efficiency of up to 96% is achieved using a novel diode laser system consisting of two narrowband modules with a combined output power of 80 W ex fiber. The utilization of multiple pump wavelengths allows for both substantial power scaling and reduction of the laser threshold, thus providing a low power consuming laser system feasible for LIDAR applications.

Narrowband

Optical Pumping

Erbium

10.1117/12.2080232

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Analysis of laser-fired local back surface fields using n/sup +/np/sup +/ cell structures

3rd World Conference onPhotovoltaic Energy Conversion, 2003. Proceedings of (2003)

Stefan W. Glunz A. Grohe Martin Hermle E. Schneiderlöchner J. Dicker

In order to investigate our new LFC process for the formation of local contacts on a dielectrically passivated rear surface, we have analyzed n/sup +/np/sup +/ structures processed identically to the standard n/sup +/pp/sup +/ cells except for the doping type of the base material. For these devices the p/sup +/-emitter is formed point-like at the rear surface by Al-alloying during the LFC process. The observation of voltages above 600 mV is a clear proof of the creation of a local Al diffusion. Since a pn-junction is much more decisive for a solar cell than a BSF, the n/sup +/np/sup +/ structures were used to understand the physics of the LFC contact and to optimize the laser parameters resulting in efficiencies of 20% for n/sup +/pp/sup +/ LFC cells in a resistivity range between 0.5 /spl Omega/cm and 10 /spl Omega/cm.

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Fully Ion Implanted and Coactivated Industrial n-Type Cells With 20.5% Efficiency

IEEE Journal of Photovoltaics (2013)

T. S. Böscke D. Kania C. Schöllhorn D. Stichtenoth A. Helbig

We present our progress in fully implanted n-type cell for industrial manufacturing. Screen-printed n-type cells with boron emitters are a viable contender to succeed p-type cell in industrial production. A major open topic is the availability of a robust manufacturing flow. The synergistic qualities of ion implantation allow for a very efficient and potentially robust process sequence. We review some of the challenges arising from this approach, such as activation of the implanted boron emitter and the reverse current characteristics. Or current process allows manufacturing of 156 × 156 mm ² cells with efficiencies up to 20.5% with a single coactivation anneal.

10.1109/jphotov.2013.2287760

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Citations (33)

Selective Laser Ablation of Anti-Reflection Coatings for Novel Metallization Techniques

A. Grohe C. Harmel A. Knorz Stefan W. Glunz R. Preu

The industrial standard process for producing solar cell front sides includes several drawbacks. First of all the screen-printed front side metallisation with silver paste leads to contacts with a poor aspect ratio and a low conduction quality due to the composition of a printable paste. Additionally, the poor contact resistance requires high surface doping concentrations of the emitter. When using further developed cell concepts like the laser-fired contacted rear side (LFC) featuring dielectric passivation and a local point contact structure, the high-temperature step for establishing the front contact is detrimental too. A solution for this problem could be the use of alternative front side metallisation techniques. Without firing through they all require a selective opening of the front side antireflection coating. The approach studied in this paper is the selective laser ablation of this layer

Passivation

Laser Ablation

Screen printing

Contact resistance

Reflection

10.1109/wcpec.2006.279713

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Citations (9)

The Status of Silicon Solar Cell Production Technology Development at Fraunhofer ISE

R. Preu D. Bíro J. Rentsch Florian Clement D. Erath

The development of new production technologies for crystalline silicon solar cells has been very actively addressed by both research institutes and industry in the past ten years due to the increased economical value of photovoltaic energy conversion. In this paper we describe selected approaches being followed at Fraunhofer ISE in order to support the cost reduction objectives. A simple screen-printing reference process was developed with an efficiency potential of 18% for mono-crystalline silicon wafers. The set up of the Photovoltaic-Technology Evaluation Center (PV-TEC) enables a fast evaluation of new technologies on pilot scale throughput of several hundred wafers/hour

Silicon solar cell

10.1109/wcpec.2006.279318

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Aluminum-Based Rear-Side PVD Metallization for nPERT Silicon Solar Cells

IEEE Journal of Photovoltaics (2013)

K. Katkhouda Alberto Martinez-Limia L. Bornschein Radinka Koseva T. Geppert

This paper presents the results of a detailed study on Al-based physical vapor deposition metallization for the rear side of nPERT silicon solar cells. Pure Al is compared with a barrier metallization (Al-Si/Al or Ti/Al) in terms of spiking, contact formation and back-side reflection. A degradation of cell performance with pure Al rear-side metallization due to Al spiking after thermal annealing is observed. This can be avoided either by using a spiking barrier or by using a sufficiently deep doping profile. In addition, all metallization schemes have a sufficiently low specific contact resistance <;0.2 mΩ·cm ² on n ⁺ -Si with a sheet resistance of ~75 Ω/sq. Furthermore, the widely used front-side contact metal Ti leads to a significant short-circuit current density loss of more than 0.3 mA/cm ² when applied to the rear side of a silicon solar cell due to its low reflectivity of infrared wavelengths.

Contact resistance

10.1109/jphotov.2013.2288018

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Citations (7)