Copper as conducting layer in advanced front side metallization processes for crystalline silicon solar cells, exceeding 20% on printed seed layers

Bartsch, Jonas; Mondon, A.; Schetter, C.; Hörteis, M.; Glunz, Stefan W.

doi:10.1109/pvsc.2010.5614244

Cited by 24 publications

(23 citation statements)

References 4 publications

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“…Moreover, the proposed replacement of expensive silver front contacts with low-cost copper-plated contacts might further increase the probability of copper contamination in the solar cell line. 5 Therefore, copper might well be the culprit behind LID in some solar cell studies. 6 Recently, much effort has been put into mitigating lightinduced degradation.…”

mentioning

confidence: 99%

Room-temperature method for minimizing light-induced degradation in crystalline silicon

Lindroos¹,

Yli-Koski²,

Haarahiltunen³

et al. 2012

Applied Physics Letters

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Although light-induced degradation (LID) in crystalline silicon is attributed to the formation of boron-oxygen recombination centers, copper contamination of silicon has recently been observed to result in similar degradation. As positively charged interstitial copper stays mobile at room temperature in silicon, we show that the bulk copper concentration can be reduced by depositing a large negative charge onto the wafer surface. Consequently, light-induced degradation is reduced significantly in both low- and high-resistivity boron-doped Czochralski-grown silicon.

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mentioning

confidence: 99%

Room-temperature method for minimizing light-induced degradation in crystalline silicon

Lindroos¹,

Yli-Koski²,

Haarahiltunen³

et al. 2012

Applied Physics Letters

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“…Ni/Cu has shown some good results for solar cell performance in terms of improved FFs and higher efficiencies. The overall cost per watt-peak (W p ) can also be decreased as the copper is cheaper than Ag (about 100 times) and is almost equally conductive [26,27]. It has been reported that Ni/Cu-in comparison to Ag paste-has higher electrical conductivity and lower contact resistance, even at lower doping concentrations (N s ) [28].…”

Section: Silver Vs Copper Metallizationmentioning

confidence: 99%

Crystalline Silicon Solar Cells with Nickel/Copper Contacts

Rehman¹,

Lee²

2015

Solar Cells - New Approaches and Reviews

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In silicon solar cell technology, metallization plays an integral part in outlining the cost and efficiency of solar cells. Indeed, the development of better techniques for the metallization of silicon solar cells is vital for achieving higher efficiencies. Presently, screen-printed contacts are primarily employed in photovoltaic industry as they can be realized easily with high throughputs. However, screen-printing technology has the draw-backs of higher contact resistance and lower aspect ratios, degrading the solar cells performance. In recent years, an overall decrease in the photovoltaic module price index has occurred, while the higher cost of silver has disturbed this decrease adversely [ ]. The future of solar cell technology will involve decreasing the wafer s thickness as well as decreasing the use of silver according to the standards set out by the international technology roadmap for photovoltaics ITRPV [ ]. Metal contacts with superior electrical performance and lower production costs are vital for photovoltaic industrial production. In short, the pressing process of screen printing technology for thinner silicon wafers, along with expensive silver pastes, needs to be replaced by a fresh metallization technology. A series of workshops have been dedicated to the metallization of crystalline silicon solar cells, where various metallization techniques have already been inquired [ -]. All of these meetings have helped in understanding and reforming present-day advancements in solar cell metallization techniques.Among the capable metallization techniques, contacts composed of nickel/copper Ni/Cu metal stacks are considered to be one of the most feasible candidates for future metallization technologies. The use of such metal stacks offers precise and low contact resistance and also helps in improving solar cells efficiency [ ]. The most important feature is that the technique can be realized with lower material costs. Ni/Cu contact formations involve two major steps a Ni seed layer formation followed by a Cu metal deposition as a front electrode. The Cu metal stack over the Ni layer plays the role of the main contact to the front of the cell [ -]. The Cu © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. front metals stack is usually formed by an electro-plating process, which is a well-developed plating technique and can only be applied to conductors. Cu has also been deposited by an electroless plating process, but it also requires a seed layer at the silicon surface [ , ]. An auto-catalytic method of depositing Ni-phosphorus or Ni-boron by electroless plating bath compositions can be adopted to contact the semiconducting surface of silicon [ -]. The use of a seed layer i.e., Ni can help to plate metal stacks on semiconducting or even nonconducting materials. Ap...

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“…There is an industrial push to replace the Ag front electrode 3,4]. The Ni layer is a barrier to block Cu diffusion into Si, which degrades the efficiency of the cell.…”

Section: Introductionmentioning

confidence: 99%

Zn as the protective layer for Cu electrode in wafer-Si solar cells

Han

Zhou

Yang

et al. 2014

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC)

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Zn is proposed as the protective layer for the Cu electrode in wafer-Si solar cells to replace today's Ag front electrode. Zn provides a lower material cost, a lower resistivity and more abundant material reserve than Sn. The thermal stability of the Zn/Cu/Ni stack is examined by annealing it in air and the Zn/Cu/Ni stack is advantageous over the Sn/Cu/Ni stack in thermal stability. This is attributed to the better coverage of electroplated Zn on Cu and the higher melting point of Zn over Sn. The sheet resistance of the Zn/Cu/Ni stack is also lower than the Sn/Cu/Ni stack due to the lower resistivity of Zn. XRD measurements before and after annealing confirms that the increased sheet resistance upon annealing is due to oxidation and alloying of the Cu layer. For solderability, a Sn/Zn/CulNi stack with reduced Sn thickness is demonstrated by sequential electroplating.

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Copper as conducting layer in advanced front side metallization processes for crystalline silicon solar cells, exceeding 20% on printed seed layers

Cited by 24 publications

References 4 publications

Room-temperature method for minimizing light-induced degradation in crystalline silicon

Room-temperature method for minimizing light-induced degradation in crystalline silicon

Crystalline Silicon Solar Cells with Nickel/Copper Contacts

Zn as the protective layer for Cu electrode in wafer-Si solar cells

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