Development of Cu plating for silicon heterojunction solar cells

Aguilar, Antony; Herasimenka, Stanislau; Karas, Joseph; Jain, Harsh; Lee, Jongwon; Munoz, Krystal; Michaelson, Lynne; Tyson, Tom; Dauksher, William J.; Bowden, Stuart

doi:10.1109/pvsc.2016.7749972

Cited by 15 publications

(8 citation statements)

References 9 publications

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“…In fact, plating has shown to outperform low temperature screen printing due to a higher fill factor (FF) and a higher short circuit current ( J SC ) . High peel forces (3–5 N/mm) for plated copper fingers on TCO have been measured with an intermediate seed layer . In addition, plating imposes less mechanical stress onto the wafer than screen printing, which is an advantage in view of thinner wafers expected in the future .…”

Section: Parameters (Measured Under Stc) Of Two Identically Procesmentioning

confidence: 99%

“…In order to plate a grid structure on the TCO surface of SHJ cells, in most cases, a structured organic plating mask is applied, which covers the areas that should not be plated . The downside of organic masks is that the coating materials and the waste water management for chemically removing the mask are expensive.…”

Section: Parameters (Measured Under Stc) Of Two Identically Procesmentioning

confidence: 99%

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Laser Transfer and Firing of NiV Seed Layer for the Metallization of Silicon Heterojunction Solar Cells by Cu-Plating

et al. 2017

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We present a laser-based method for the metallization of silicon heterojunction solar cells by Cu-plating. It consists of first applying a dielectric layer on the transparent conductive oxide (TCO) as a plating mask. Then, a NiV seed is transferred by laser induced forward transfer (LIFT) from a plastic carrier foil onto the wafer. In the second laser step, the NiV layer is fired through the dielectric layer to form a contact to the TCO. After the laser process, Cu-fingers are produced by plating. The dielectric plating mask remains on the cell. Parasitic plating is prevented by using an advanced reverse pulse plating process. With the first solar cells we reach a maximum efficiency of 22.2% and an efficiency gain of 0.5% abs compared to lowtemperature screen printing reference cells, due to a higher short circuit current and fill factor. The 30 mm wide fingers reach specific contact resistances down to 0.6 mV cm 2 and also, pass a tape adhesion test. We further demonstrate that the laser process does not cause any measurable open circuit voltage loss and that a precise alignment of the two laser steps is not necessary.Silicon heterojunction (SHJ) solar cells are believed to play a major role in the future PV market [1] . Compared to homojunction solar cells, they offer a superior module performance due to their higher open circuit voltage and their lower temperature coefficient. Moreover, the production is relatively simple and does not require high temperature steps. However, a drawback for this technology still is the metallization. Screen printed metallization can only be applied with special expensive low temperature silver pastes [2] , because the passivation by the amorphous silicon (a-Si) layers of SHJ cells cannot withstand temperatures above 200-250 C [3] . Lowtemperature silver pastes reach resistivities between 5 and 10 mVcm [4] , which is far higher than for standard silver pastes sintered at high temperature (>800 C). The typical width of industrially produced screen printed fingers on SHJ cells lies between 60 and 80 mm.Cu-plating as a low temperature metallization is a more suitable technology. Kaneka has recently presented a plated SHJ solar cell with 25.1% efficiency, which represents the world record for both-sidecontacted SHJ solar cells [5] . Depending on the masking approach, plated fingers can be much thinner than screen printed fingers and the resistivity of plated metal is very close to that of bulk Cu (1.7 mVcm). In fact, plating has shown to outperform low temperature screen printing due to a higher fill factor (FF) [6] and a higher short circuit current (J SC ) [7] . High peel forces (3-5 N/mm) for plated copper fingers on TCO have been measured with an intermediate seed layer [8,9] . In addition, plating imposes less mechanical stress onto the wafer than screen printing, which is an advantage in view of thinner wafers expected in the future [1] .In order to plate a grid structure on the TCO surface of SHJ cells, in most cases, a structured organic plating mask is applied, which covers...

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Section: Parameters (Measured Under Stc) Of Two Identically Procesmentioning

confidence: 99%

Section: Parameters (Measured Under Stc) Of Two Identically Procesmentioning

confidence: 99%

Laser Transfer and Firing of NiV Seed Layer for the Metallization of Silicon Heterojunction Solar Cells by Cu-Plating

et al. 2017

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“…On the other hand, a plated metallization is intrinsically a low temperature process. Plated approaches using highly conductive and less expensive copper are currently investigated . The Cu‐based contacts can be electroplated simultaneously on both‐sides of the solar cells and TCOs like indium‐tin‐oxide (ITO) are good barrier to metals diffusion into silicon .…”

Section: Introductionmentioning

confidence: 99%

“…Plated approaches using highly conductive and less expensive copper are currently investigated. [12][13][14][15][16][17][18][19][20] The Cu-based contacts can be electroplated simultaneously on bothsides of the solar cells and TCOs like indium-tin-oxide (ITO) are good barrier to metals diffusion into silicon. [21] This manufacturing of plated bifacial SHJ solar cells intends to increase the contacts conductivity and reduces drastically the precious Ag consumption.…”

Section: Introductionmentioning

confidence: 99%

Native Oxide Barrier Layer for Selective Electroplated Metallization of Silicon Heterojunction Solar Cells

et al. 2019

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The metallization of silicon heterojunction (SHJ) solar cells by electroplating of highly conductive copper onto a multifunctional patterned metal layer stack is demonstrated. The approach features several advantages: low temperature processing, high metal conductivity of plated copper, no organic making, and low material costs (almost Ag‐free). A PVD layer stack of copper and aluminum is deposited onto the cell subsequently to TCO deposition. The aluminum layer is patterned with a printed etchant and its native oxide on the remaining areas inhibits plating. The full area aluminum layer while electroplating supports plating current distribution and allows homogeneous plating height distributions over the cell. The NOBLE (native oxide barrier layer for selective electroplating) approach allows reaching a first encouraging SHJ solar cell efficiency of 20.2% with low contact resistivity.

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“…8) To improve the adhesion of the ITO and the copper interface, a thin metal seed layer, which is deposited by physical vapor deposition (PVD) or light-induced plating (LIP), has been investigated with some materials such as Ni, Ti, Cr, and Ag. 21) When a seed layer is applied on the ITO layer for better adhesion, contact resistivity (ρ c ) also needs to be considered since a high series resistance degrades the fill factor of solar cells. In this paper, we investigated various metal coevaporated copper layers (Cu-X) as seed layers on the ITO since there is a possibility of improving adhesion between the seed layer and the ITO layer.…”

Section: Introductionmentioning

confidence: 99%

Contact resistivity and adhesion of copper alloy seed layer for copper-plated silicon heterojunction solar cells

Lee

et al. 2018

Jpn. J. Appl. Phys.

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To reduce optical loss and contact material cost in silicon heterojunction (SHJ) solar cells, copper plating has been considered as a suitable metallization technique. However, a plated copper contact on indium tin oxide (ITO) generally has low adhesion reliability. For this reason, suitable seed layer materials are required for adhesive copper plating. As a requirement of a suitable seed layer material, contact resistance between the seed and the ITO is also important, as well as the adhesion, since a high series resistance results in a low fill factor. In this work, we applied copper alloy (Cu-X) materials as a seed layer that was deposited by co-evaporating copper with other metals. The contact resistivity (ρ c ) values of the Cu-X seed layer and copper-plated contact with the Cu-X seed layer (Cu-X/Cu) on the ITO layer were evaluated by the transfer length method (TLM). Also, tape tests were carried out to check the adhesion of the Cu-X/Cu contact.

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Development of Cu plating for silicon heterojunction solar cells

Cited by 15 publications

References 9 publications

Laser Transfer and Firing of NiV Seed Layer for the Metallization of Silicon Heterojunction Solar Cells by Cu-Plating

Laser Transfer and Firing of NiV Seed Layer for the Metallization of Silicon Heterojunction Solar Cells by Cu-Plating

Native Oxide Barrier Layer for Selective Electroplated Metallization of Silicon Heterojunction Solar Cells

Contact resistivity and adhesion of copper alloy seed layer for copper-plated silicon heterojunction solar cells

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