Industrial PVD metallization for high efficiency crystalline silicon solar cells

Nekarda, Jan; Reinwand, Dirk; Grohe, A.; Hartmann, Philip; Preu, R.; Trassl, R.; Wieder, S.

doi:10.1109/pvsc.2009.5411146

Cited by 20 publications

(11 citation statements)

References 3 publications

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“…In addition, lower specific contact resistance for Al/Si (<0.5 mΩ∙cm 2 ) has also been reported, compared with the Ag/Si (1–2 mΩ∙cm 2 ) . Because the sheet resistance of a 2‐µm‐thick PVD Al layer is just ~0.015 Ω/□ , a thin (1 ~ 2 µm) PVD Al layer on the entire rear area is sufficient to meet the required electrical conductance for large‐area Si solar cells, which further leads to less wafer bow and less Al consumption . On the other hand, in order to obtain a good solder contact to the PVD Al side, depositing a double layer of Ni : V/Ag with respective thickness of 200 and 25 nm on top of PD Al layer can offer an excellent solderability with a peel force greater than 3 N/mm and long‐term stability .…”

Section: Introductionmentioning

confidence: 99%

20.7% efficient ion‐implanted large area n‐type front junction silicon solar cells with rear point contacts formed by laser opening and physical vapor deposition

Tao

Payne

Upadhyaya

et al. 2014

Progress in Photovoltaics

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In this work, we report on ion-implanted, high-efficiency n-type silicon solar cells fabricated on large area pseudosquare Czochralski wafers. The sputtering of aluminum (Al) via physical vapor deposition (PVD) in combination with a laserpatterned dielectric stack was used on the rear side to produce front junction cells with an implanted boron emitter and a phosphorus back surface field. Front and back surface passivation was achieved by thin thermally grown oxide during the implant anneal. Both front and back oxides were capped with SiN x , followed by screen-printed metal grid formation on the front side. An ultraviolet laser was used to selectively ablate the SiO 2 /SiN x passivation stack on the back to form the pattern for metal-Si contact. The laser pulse energy had to be optimized to fully open the SiO 2 /SiN x passivation layers, without inducing appreciable damage or defects on the surface of the n + back surface field layer. It was also found that a low temperature annealing for less than 3 min after PVD Al provided an excellent charge collecting contact on the back. In order to obtain high fill factor of~80%, an in situ plasma etching in an inert ambient prior to PVD was found to be essential for etching the native oxide formed in the rear vias during the front contact firing. Finally, through optimization of the size and pitch of the rear point contacts, an efficiency of 20.7% was achieved for the large area n-type passivated emitter, rear totally diffused cell.

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Section: Introductionmentioning

confidence: 99%

20.7% efficient ion‐implanted large area n‐type front junction silicon solar cells with rear point contacts formed by laser opening and physical vapor deposition

Tao

Payne

Upadhyaya

et al. 2014

Progress in Photovoltaics

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“…4 Vacuum evaporation is wellestablished in the packaging industry as a low cost, large area deposition method for the fabrication of thin metal films and is compatible with roll-to-roll deposition onto flexible substrates, as well as offering the necessary high degree of control over metal film thickness. 5 The potential of this approach to achieve comparable device performance to conventional device architectures based on a conducting oxide window electrode has been demonstrated in wholly vacuum deposited small molecule OPVs by the group of Leo, 6 using Ag as the base metal for the transparent electrode. Ag is the metal of choice for this application because it has the highest conductivity 7 and the lowest optical absorbance 8 of the earth abundant metals over the visible spectrum, combined with relatively high stability toward oxidation in air.…”

Section: ■ Introductionmentioning

confidence: 99%

Widely Applicable Coinage Metal Window Electrodes on Flexible Polyester Substrates Applied to Organic Photovoltaics

Stec

Hatton

2012

ACS Appl. Mater. Interfaces

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The fabrication, exceptional properties, and application of 8 nm thick Cu, Ag, Au, and Cu/Ag bilayer electrodes on flexible polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates is reported. These electrodes are fabricated using a solvent free process in which the plastic surface is chemically modified with a molecular monolayer of thiol and amine terminated alkylsilanes prior to metal deposition. The resulting electrodes have a sheet resistance of ≤14 Ω sq–1, are exceptionally robust and can be rapidly thermally annealed at 200 °C to reduce their sheet resistance to ≤9 Ω sq–1. Notably, annealing Au electrodes briefly at 200 °C causes the surface to revert almost entirely to the {111} face, rendering it ideal as a model electrode for fundamental science and practical application alike. The power conversion efficiency of 1 cm2 organic photovoltaics (OPVs) employing 8 nm Ag and Au films as the hole-extracting window electrode exhibit performance comparable to those on indium–tin oxide, with the advantage that they are resistant to repeated bending through a small radius of curvature and are chemically well-defined. OPVs employing Cu and bilayer Cu:Ag electrodes exhibit inferior performance due to a lower open-circuit voltage and fill factor. Measurements of the interfacial energetics made using the Kelvin probe technique provide insight into the physical reason for this difference. The results show how coinage metal electrodes offer a viable alternative to ITO on flexible substrates for OPVs and highlight the challenges associated with the use of Cu as an electrode material in this context.

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“…The area‐weighted resistance in the finger can be determined in the case of linearly increasing current by

{italicR}_{italics} = \frac{1}{3} ρ \frac{i {italicl}_{normalF}^{2}}{A_{F}}

with ρ = 3.2 μΩ cm being the resistivity of the evaporated aluminum , i = 2.3 mm the index width of the fingers, l F the length of the fingers, and A F the cross‐section area of the fingers perpendicular to the direction of transport of the current. The thickness of the Al layer is 25 µm.…”

Section: Analysis Of Gains and Lossesmentioning

confidence: 99%

Interconnection of busbar‐free back contacted solar cells by laser welding

Schulte‐Huxel

Blankemeyer

Merkle

et al. 2014

Progress in Photovoltaics

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We are presenting the module integration of busbar‐free back‐junction back‐contact (BJBC) solar cells. Our proof‐of‐concept module has a fill factor of 80.5% and a conversion efficiency on the designated area of 22.1% prior to lamination. A pulsed laser welds the Al metallization of the solar cells to an Al foil carried by a transparent substrate. The weld spots electrically contact each individual finger to the Al foil, which serves as interconnect between different cells. We produce a proof‐of‐concept module using busbar‐free cell strips of 25 × 125 mm2. These are obtained by laser‐dicing of a 125 × 125 mm2 BJBC solar cell. The fill factor of this module is increased by 3.5% absolute compared with the initial cell before laser‐dicing. This is achieved mainly by omitting the busbars and reduction of the finger length. The improvement of the module fill factor results in an increase in the module performance of 0.9% absolute before lamination in comparison with the efficiency of the initial 125 × 125 mm2 BJBC solar cell. Hence, this interconnection scheme enables the transfer of high cell efficiencies to the module. Copyright © 2014 John Wiley & Sons, Ltd.

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Industrial PVD metallization for high efficiency crystalline silicon solar cells

Cited by 20 publications

References 3 publications

20.7% efficient ion‐implanted large area n‐type front junction silicon solar cells with rear point contacts formed by laser opening and physical vapor deposition

20.7% efficient ion‐implanted large area n‐type front junction silicon solar cells with rear point contacts formed by laser opening and physical vapor deposition

Widely Applicable Coinage Metal Window Electrodes on Flexible Polyester Substrates Applied to Organic Photovoltaics

Interconnection of busbar‐free back contacted solar cells by laser welding

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