Effect of oxygen partial pressure on Ag crystallite formation at screen-printed Pb-free Ag contacts of Si solar cells

Huh, Joo Youl; Hong, Kyoung Kook; Cho, Sung Bin; Park, Sung Kyun; Lee, Byung Chul; Okamoto, Kuninori

doi:10.1016/j.matchemphys.2011.07.075

Cited by 26 publications

(24 citation statements)

References 14 publications

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“…According to the model proposed by Hong et al . , the presence of Ag particles at the contact interface is indicative of a redox reaction involving the Ag + ions dissolved in the molten glass, as the Ag + ions themselves cannot precipitate owing to electrostatic repulsion among them . The Ag + ions can be reduced to precipitate as Ag particles by reacting with either the SiN x layer or the Si emitter:

{4 A g}^{prefix+}_{(in glass)} {+ 2 O}^{2 -}_{(in glass)} {+ SiN}_{x}_{(s)} \to {4 A g}^{normalo}_{(in glass)} + {normalS normali normalO}_{2 ((), italicin glass)} prefix+ \frac{x}{2} {normalN}_{2}_{(g)},

4 {A g}^{prefix+}_{(in glass)} {+ 2 O}^{2 -}_{(in glass)} prefix+ {normalS normali}_{(s)} \to {4 A g}^{normalo}_{(in glass)} + {S i O}_{2}_{(in glass)} .

…”

Section: Resultsmentioning

confidence: 99%

“…According to the model proposed by Huh et al . , during the firing process, the molten glass acts as a medium for dissolving and transporting Ag + and O 2− ions, which are the active species reacting with the SiN x :H and Si emitter layers. In fact, when a lead borosilicate glass was reacted with Ag powder at 800 °C under an oxygen‐containing atmosphere, electrochemical analyses revealed that the Ag + concentration in the molten glass increased with increasing oxygen content in the reaction atmosphere, and that the equilibrium reduction potential of Ag + /Ag was much nobler than that of Pb 2+ /Pb in the lead borosilicate melt .…”

Section: Introductionmentioning

confidence: 99%

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Electrochemical nature of contact firing reactions for screen‐printed silicon solar cells: origin of “gray finger” phenomenon

Kim

Cho

Kim

et al. 2016

Progress in Photovoltaics

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Fire-through Ag thick-film metallization of crystalline Si (c-Si) solar cells often yields macroscopically non-uniform contact quality over the cell area, degrading the cell performance and causing cell-to-cell variations of the conversion efficiency in a cell production line. This study analyzes the root cause of the "gray finger" phenomenon, in which part of the firethrough Ag contact gridlines of a c-Si solar cell appears in gray or dark contrast in the electroluminescence images owing to high contact resistance. Few Ag crystallites were formed on the corrugated emitter surface at the contact interfaces underneath the gray fingers. The present results revealed that the gray finger phenomenon was caused by a short-circuit spot that formed between the Ag gridlines and underlying Si emitter during contact firing. The electrochemical reactions involved in fire-through Ag contact formation established a potential difference between the sintered Ag gridlines and Si emitter separated by molten glass. The molten glass acted as an electrolyte containing mobile Ag + and O 2À ions during contact firing. Therefore, the short-circuiting between the sintered Ag gridlines and Si emitter produced a galvanic cell during contact firing, which inhibited Ag crystallite formation at the contact interface along the gridlines in a short circuit and produced the gray fingers. The firing reactions in Ag thick-film contact formation could be interpreted in terms of the mixed potential theory of corrosion. The degradation of cell performance because of the gray finger phenomenon was also evaluated for 6-in. screen-printed c-Si solar cells.

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{4 A g}^{prefix+}_{(in glass)} {+ 2 O}^{2 -}_{(in glass)} {+ SiN}_{x}_{(s)} \to {4 A g}^{normalo}_{(in glass)} + {normalS normali normalO}_{2 ((), italicin glass)} prefix+ \frac{x}{2} {normalN}_{2}_{(g)},

4 {A g}^{prefix+}_{(in glass)} {+ 2 O}^{2 -}_{(in glass)} prefix+ {normalS normali}_{(s)} \to {4 A g}^{normalo}_{(in glass)} + {S i O}_{2}_{(in glass)} .

…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrochemical nature of contact firing reactions for screen‐printed silicon solar cells: origin of “gray finger” phenomenon

Kim

Cho

Kim

et al. 2016

Progress in Photovoltaics

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“…This can be a hint for a possible emitter etch through. It was discussed elsewhere that a controlled o xygen content in the firing atmosphere could be used for controlling the size of the silver precip itations and inhibit a overgrow of the silver crystallites [3] . In figure 4 the selective etch back pictures for the four inorganic additives are shown.…”

Section: Methodsmentioning

confidence: 99%

“…Literature studies show that the amount and size of silver precip itations in the glassy interface is dependent on the oxygen pressure in the oven atmosphere [2,3,4] .…”

Section: Introductionmentioning

confidence: 99%

Influence of Oxygen Micro Atmosphere During Contact Formation

et al. 2014

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“…The main issue is still the higher resistivity and lower adhesion. The main reason is still part of oxidation during the firing process [4,5]. In our work, we use N 2 protection during the firing which gave us the better resistivity and adhesion of the paste.…”

Section: Introductionmentioning

confidence: 99%

Low cost Rear Ag paste using doping silver plated-coated Copper and Tin powder under N<inf>2</inf> protection firing

Yang

Shen

Zhang

et al. 2013

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC)

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Low cost Rear Ag paste is made by silver platedcoated Copper and Tin powder to replace part of pure Ag powder in the paste to reduce the cost of solar cell manufacture and also improve the adhesion of the solar cell busbar. The key issue to use Ag coated copper and tin is the oxidization of cooper and tin during the drying and firing process which will reduce the solderability and adhesion by using this system. We use N2 protection during drying and firing process to prevent the oxidization of cooper and tin. Therefore, the solderability and adhesion has been increased a lot to achieve the industry testing standard. Also Rs reduction is also a big achievement for this paste system.

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Effect of oxygen partial pressure on Ag crystallite formation at screen-printed Pb-free Ag contacts of Si solar cells

Cited by 26 publications

References 14 publications

Electrochemical nature of contact firing reactions for screen‐printed silicon solar cells: origin of “gray finger” phenomenon

Electrochemical nature of contact firing reactions for screen‐printed silicon solar cells: origin of “gray finger” phenomenon

Influence of Oxygen Micro Atmosphere During Contact Formation

Low cost Rear Ag paste using doping silver plated-coated Copper and Tin powder under N<inf>2</inf> protection firing

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