Comparison of innovative metallization approaches for silicon heterojunction solar cells

Erath, D.; Pospischil, Maximilian; Keding, Roman; Jahn, Mike; Lontchi, Igor Lacmago; Lorenz, Andreas; Clement, Florian

doi:10.1016/j.egypro.2017.09.245

Cited by 25 publications

(19 citation statements)

References 4 publications

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“…Screen printed metallization can only be applied with special expensive low temperature silver pastes , because the passivation by the amorphous silicon (a‐Si) layers of SHJ cells cannot withstand temperatures above 200–250 °C . Low‐temperature silver pastes reach resistivities between 5 and 10 µΩcm , 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 μm.…”

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%

“…As a reference, we produced solar cells with our base‐line low‐temperature screen‐printing process . The grid was printed on the front side of the precursors.…”

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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“…The reason may be defrosting during shipping of the paste which deteriorated its quality. 7-10 µcm have already been reported for this paste [7] which is used as the reference here. Paste AU achieves its lowest lateral resistivity after thermal curing.…”

Section: -6mentioning

confidence: 99%

“…These pastes are thermally activated in the range of 200°C and are recommended by paste manufacturers to be cured for 15-30 min. Then, the screen-printed contact fingers exhibit lateral resistivities (specific resistances lengthways the fingers)  l of above 6 µcm [5][6][7]. This is correlated with significant ohmic losses and a reduced efficiency on cell level.…”

Section: Introductionmentioning

confidence: 99%

Applicability of photonic sintering and autoclaving as alternative contact formation methods for silicon solar cells with passivating contacts

Schube¹,

Fellmeth²,

Maier³

et al. 2018

AIP Conference Proceedings

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“…Metal pastes printed on SHJ solar cells are designed for low‐temperature application, due to the thermal sensitivity of the amorphous layers. As the cells cannot be heated to above 200 °C, the conductivity of the metal paste is relatively low . This problem has been partly reduced by application of the smart wire technology, which can directly interconnect printed contact fingers with small solder‐coated wires that form the module interconnect .…”

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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Comparison of innovative metallization approaches for silicon heterojunction solar cells

Cited by 25 publications

References 4 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

Applicability of photonic sintering and autoclaving as alternative contact formation methods for silicon solar cells with passivating contacts

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

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