Laser ablation of SiO<sub>2</sub> for locally contacted Si solar cells with ultra‐short pulses

Engelhart, P.; Hermann, Sonja; Neubert, T.; Plagwitz, Heiko; Grischke, R.; Meyer, Rüdiger; Klug, Ulrich; Schoonderbeek, Aart; Stute, U.; Brendel, Rolf

doi:10.1002/pip.758

Cited by 88 publications

(42 citation statements)

References 5 publications

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“…The ''selective'' emitter (SE) concept uses laterally different emitter doping: (i) high doping under the front side metallization for low contact resistance between contact metal and semiconductor interface, (ii) lower doping between the contact fingers for a better short wavelength response due to less Auger recombination [1] as well as improved emitter passivation [2,3]. Unfortunately, most SE concepts developed so far in research imply a high process complexity due to the required masking steps for selective diffusion [4] or emitter etch back [5]. In particular, such existing concepts are hard to implement into industrial production of solar cells.…”

Section: Introductionmentioning

confidence: 99%

Add‐on laser tailored selective emitter solar cells

Roder

Eisele

Grabitz³

et al. 2010

Progress in Photovoltaics

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An elegant laser tailoring add-on process for silicon solar cells, leading to selectively doped emitters increases their efficiency h by Dh ¼ 0.5% absolute. Our patented, scanned laser doping add-on process locally increases the doping under the front side metallization, thus allowing for shallow doping and less Auger recombination between the contacts. The selective laser add-on process modifies the emitter profile from a shallow error-function type to Gaussian type and enables excellent contact formation by screen printing, normally difficult to achieve for shallow diffused emitters. The significantly deeper doping profile of the laser irradiated samples widens the process window for the firing of screen printed contacts and avoids metal spiking through the pn-junction.

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Section: Introductionmentioning

confidence: 99%

Add‐on laser tailored selective emitter solar cells

Roder

Eisele

Grabitz³

et al. 2010

Progress in Photovoltaics

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“…This contact diffusion in region 4 is equivalent to a sheet resistance value of 20 Ω/sq. As discussed elsewhere [8,11,12], we also have an alternative technique available for achieving virtually damage-free openings in the SiO 2 layer by using an ultra short pulse picosecond laser. This technology avoids any need for damage etching after opening SiO 2 layers and therefore provides process flexibility as well as a simplification of the process sequence.…”

Section: Contributedmentioning

confidence: 99%

Laser‐processed high‐efficiency silicon RISE‐EWT solar cells and characterisation

Harder

Hermann

Merkle

et al. 2009

Phys. Status Solidi (c)

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The RISE‐EWT (Rear Intendigitated Single Evaporation Emitter Wrap Through) solar cell is a silicon wafer‐based solar cell concept that is capable of achieving solar energy conversion efficiencies of over 21%. The fabrication sequence is based exclusively on industrially feasible processing steps and avoids any photolithography and masking steps, nor does it require boron diffusion. For low process complexity, the RISE‐EWT solar cell can be made with only a single phosphorus diffusion and a single evaporation step for metallisation. All structuring of the cell is based on non‐contacting laser processing. Laser technology is the key tool for processing RISE‐EWT solar cells: The cell has laser drilled and phosphorus‐diffused holes to connect the emitter layer on the front side with the emitter and the contacts on the rear side. The emitter and base contact regions are defined by laser ablation of a diffusion barrier and KOH etch prior to phosphorus diffusion. An important feature of RISE‐EWT solar cells are steep surface features (flanks) that are produced by the laser ablation and KOH‐etching. We use these flanks to achieve reliable separation between the contacts to the n ‐type polarity and to the p ‐type polarity of the solar cell. We provide a description of RISE‐EWT manufacturing process and present an analysis of the recombination losses in our cells. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…The average effective minority carrier lifetime (t eff ) is measured by means of microwave-induced photo-conductance decay (MW-PCD) at the injection level of about 10 16 atoms/cm 3 . The SE1 cell shows lower average lifetime, LBIC and contact resistance which is mainly due to the laser-induced defect and increasing minority carrier recombination [8]. It is worth noting that the contact resistance for the SE1 cell could be also affected in this experiment.…”

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confidence: 92%

Advanced selective emitter structures by laser opening technique for industrial mc-Si solar cells

Cheng

Liou

et al. 2010

Electron. Lett.

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A laser opening technique is employed as the photolithography process to form selective emitter (SE) structures on multi-crystalline silicon (mc-Si) substrates for the large-area (156 × 156 mm 2 ) solar-cell industry. The best efficiency of 16.35% is obtained with the developed SE structure after a damage removal process with optimisation of heavily and lightly doped dopants, which yields a gain of 0.88% absolute compared with that of a reference cell. Significantly, the SE mc-Si solar cell without the damage removal process can also reach a gain of 0.48% absolute. The developed SE process has simplicity, reliability, is fast, cost-effective, and could be effectively applied to mass production in industrial applications.Introduction: The common crystalline-silicon (C-Si) solar cell for commercial application is about 40 -50 V/sq with homogeneous doping in the emitter region. This method can reduce contact resistance in the metal -semiconductor interface. However, it would increase surface recombination velocity, thus decreasing the performance of cells [1]. To overcome these disadvantages, a trade-off compromise could be obtained by a selective emitter (SE) structure [2, 3], which has heavily doped dopants (HDDs) underneath the contact metal, and lightly doped dopants (LDDs) in the illuminated area. This leads to reduced contact resistance as well as lower surface recombination velocity, thus resulting in the improved performance of cells.Recently, much effort has been made to prepare large-area SE solar cells by many approaches, such as etching paste [2], laser doping [3] and etching back [4]. In the case of etching paste, it has the advantages of being fast, simple and of reliable process. Furthermore, it is possible to achieve a low-cost production concept. But the etching paste method has some disadvantages, such as dilation of line-width in the opening region, and leads to an increase of the HDD region, thus increasing the surface recombination velocity. In the case of laser doping, the remaining phosphosilicate glass (PSG) on the wafer serves as a dopant source. The laser selectively melts the Si and locally increases the amount of phosphorus (P) in the emitter as well as driving it deeper into the wafer, thus lowering the emitter sheet resistance underneath the metal contact. However, this laser doping process leads to reduction of open-circuit voltage (Voc) and filled factor (FF) owing to laser-induced damage. In addition, etch-back techniques are based on the selective etching of the homogeneous emitter using the metallisation scheme to form an SE. The SE was obtained by etching-back nonprotected regions in an acidic etch bath of HF/HNO 3 until it reached the appropriate sheet resistance. This drawback is that the etching solution is hard to set accurately, thus lowering the reproducibility in industrial applications. Laser processing as a photolithography step is an important tool for C-Si solar cell fabrication. Recently, many processing technologies have utilised lasers in C-Si solar cell fabrication,...

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Laser ablation of SiO₂ for locally contacted Si solar cells with ultra‐short pulses

Cited by 88 publications

References 5 publications

Add‐on laser tailored selective emitter solar cells

Add‐on laser tailored selective emitter solar cells

Laser‐processed high‐efficiency silicon RISE‐EWT solar cells and characterisation

Advanced selective emitter structures by laser opening technique for industrial mc-Si solar cells

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Laser ablation of SiO2 for locally contacted Si solar cells with ultra‐short pulses

Cited by 88 publications

References 5 publications

Add‐on laser tailored selective emitter solar cells

Add‐on laser tailored selective emitter solar cells

Laser‐processed high‐efficiency silicon RISE‐EWT solar cells and characterisation

Advanced selective emitter structures by laser opening technique for industrial mc-Si solar cells

Contact Info

Product

Resources

About

Laser ablation of SiO₂ for locally contacted Si solar cells with ultra‐short pulses