Laser Metal Bonding (LMB) - low impact joining of thin aluminum foil to silicon and silicon nitride surfaces

John, Oliver; Paschen, Jan; Rose, Angela De; Steinhauser, Bernd; Emanuel, G.; Brand, Andreas A.; Nekarda, Jan

doi:10.1016/j.procir.2020.09.109

Cited by 9 publications

(5 citation statements)

References 10 publications

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“…The rest of the samples (Group II) are cleaved in half. The p-type samples are metalized with four aluminum stripes on the front side, using a laser metal bonding method [57]. This has the advantage of heating the sample only locally on the contacts, which is important to prevent influences on the overall hydrogen configuration.…”

Section: A Sample Preparationmentioning

confidence: 99%

The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation

Hammann

Aßmann

Weiser

et al. 2023

IEEE J. Photovoltaics

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In this article, the impact of different hydrogen configurations and their evolution on the extent and kinetics of light-and elevated-temperature-induced degradation (LeTID) is investigated in float-zone silicon via charge carrier lifetime measurements, lowtemperature Fourier-transform infrared spectroscopy, and fourpoint-probe resistance measurements. Degradation conditions were light soaking at 77 °C and 1 sun-equivalent illumination intensity and dark anneal at 175 °C. The initial configuration of hydrogen is manipulated by varying the wafer thickness, the cooling ramp of the fast-firing process, and the dopant type (B-or P-doped). We find lower hydrogen concentrations in thinner samples and samples with a slower cooling ramp. This suggests that hydrogen diffuses out of the sample during the cool-down, which strongly affects the final concentration of hydrogen molecules H 2 , and to a smaller degree the concentration of boron-hydrogen (BH) pairs. A regeneration of potential LeTID defects and a presumed LeTID degradation during dark annealing is found in n-type Si. In p-type Si, the LeTID extent was found to scale with H 2 , suggesting a direct link between both. The temporal evolution of BH pairs, LeTID degradation/regeneration, and surface degradation depends on wafer thickness and the cooling ramp of the fast-firing process. Based upon these findings, we formulate a theory of the hydrogen-related

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Section: A Sample Preparationmentioning

confidence: 99%

The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation

Hammann

Aßmann

Weiser

et al. 2023

IEEE J. Photovoltaics

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“…Afterward, thin aluminum stripes were attached to the bare silicon along the opened lines allowing for good ohmic contact using the FoilMet technology. [ 49 ] These electrodes were used for four‐point probe measurements of the resistance (Keithley 2002), which was translated into changes in the B–H pair concentration via

Δ false[BH false] = p_{init} - p

where p and p init denote the current and the (initial) reference hole concentration, respectively. Because the distance between the inner two electrodes was larger than the sensed region of the lifetime tester, the effective lifetime could still be measured on the same sample.…”

Section: Methodsmentioning

confidence: 99%

Hydrogen Reactions in c‐Si:B During Illumination at Room Temperature

Kwapil

Hammann

2023

Solar RRL

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Herein, effects related to reactions involving hydrogen during carrier injection at room temperature in boron‐doped Czochralski‐grown silicon wafers are investigated. It is shown that these conditions lead to boron–oxygen defect regeneration. Under these conditions, bulk material quality degradation induced by a dark annealing can be temporarily recovered in the same way as light and elevated temperature‐induced degradation. Dissociation of boron–hydrogen pairs by carrier injection at room temperature is observed in parallel. These observations are discussed within the framework of known hydrogen reactions. With this study, significant aspects of hydrogen‐related meta‐stabilities at temperatures that are most relevant for solar modules in moderate climates are covered.

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“…In our novel concept, we omit the ECA and the screen‐printed busbar on both sides (Figure 1C) and replace it with an 8‐μm‐thick Al foil (EN AW‐8079). The Al foil is directly joined to the silicon nitride (SiN X ) passivation using the so‐called laser metal bond (LMB) process 42 . The Ag fingers and the Al fingers are microwelded to the foil using 300‐ to 700‐μm‐long line‐shaped joints performed with a single 1‐kW infrared continuous‐wave laser 43 leaving no necessity for busbar‐like structures.…”

Section: Methodsmentioning

confidence: 99%

“…LMB 42 is a noninvasive joining technique that enables the formation of bonds between the passivation of the cell and the Al foil without penetrating the passivation (Figure 2A). This does not create an electrical contact but a very high adhesion between the Al foil and the wafer.…”

Section: Methodsmentioning

confidence: 99%

“…The Al foil is directly joined to the silicon nitride (SiN X ) passivation using the so-called laser metal bond (LMB) process. 42 The Ag fingers and the Al fingers are microwelded to the foil using 300-to 700-μm-long line-shaped joints performed with a single 1-kW infrared continuous-wave laser 43 leaving no necessity for busbar-like structures. The simplicity of FoilMet, which connects the fingers of adjacent cells without more intermediate layers than a single Al foil, is of great advantage compared to an ECA interconnection, with joints from the Al finger to the Ag busbar, to the ECA, to the Ag F I G U R E 1 Schematics of shingle cells and their interconnection using ECA.…”

Section: Foilmet ® -Interconnectmentioning

confidence: 99%

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FoilMet^®‐Interconnect: Busbarless, electrically conductive adhesive‐free, and solder‐free aluminum interconnection for modules with shingled solar cells

Paschen

Baliozian

John

et al. 2021

Progress in Photovoltaics

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The investigation of novel cell-to-cell interconnection methods has gained importance with the increase of wafer sizes. Shingling (i.e., overlapping) of solar cells is not only a solution for the interconnection of smaller solar cells but also a chance to increase the output power density by (i) increasing the active cell area within the module, (ii) decreasing shading losses, and (iii) reducing electrical interconnection

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Laser Metal Bonding (LMB) - low impact joining of thin aluminum foil to silicon and silicon nitride surfaces

Cited by 9 publications

References 10 publications

The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation

The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation

Hydrogen Reactions in c‐Si:B During Illumination at Room Temperature

FoilMet^®‐Interconnect: Busbarless, electrically conductive adhesive‐free, and solder‐free aluminum interconnection for modules with shingled solar cells

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Laser Metal Bonding (LMB) - low impact joining of thin aluminum foil to silicon and silicon nitride surfaces

Cited by 9 publications

References 10 publications

The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation

The Impact of Different Hydrogen Configurations on Light- and Elevated-Temperature- Induced Degradation

Hydrogen Reactions in c‐Si:B During Illumination at Room Temperature

FoilMet®‐Interconnect: Busbarless, electrically conductive adhesive‐free, and solder‐free aluminum interconnection for modules with shingled solar cells

Contact Info

Product

Resources

About

FoilMet^®‐Interconnect: Busbarless, electrically conductive adhesive‐free, and solder‐free aluminum interconnection for modules with shingled solar cells