Investigation of Modified Screen-Printing Al Pastes for Local Back Surface Field Formation

Meemongkolkiat, Vichai; Nakayashiki, Kenta; Kim, Steve; Shaikh, A.; Kuebelbeck, Armin; Stockum, W.; Rohatgi, A.

doi:10.1109/wcpec.2006.279678

Cited by 29 publications

(19 citation statements)

References 4 publications

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“…This behavior was reported before [10] and can hardly be avoided. It can, however, be influenced by the size of the opening, because contacts larger than 200 !-1m reach a saturation of Si in AI in their middle part and there the AI remains in contact with the wafer.…”

Section: Sem Contact Area Investigationmentioning

confidence: 71%

Enabling dielectric rear side passivation for industrial mass production by developing lean printing-based solar cell processes

Lauermann

Lüder

Scholz

et al. 2010

2010 35th IEEE Photovoltaic Specialists Conference

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AI203 rear-passivated large-area silicon solar cells with screen-printed metallization are demonstrated for the first time.An industrially feasible solar cell process is described that is based on printing steps to contact base and emitter of large area solar cells with dielectric rear side passivation. The base of the cell is contacted at the rear by a full area screen-printed aluminum layer on an inkjet-structured AI20a/SiNx-layer stack. The AI rear contacts are co-fired with the screen-printed silver front contacts. The firing temperature is reduced to limit deterioration of the passivation ability of the aluminum oxide layer. Synergies are exploited by combining the structuring steps for the formation of openings in the rear side dielectric by hydrofluoric acid with the selective emitter formation on the front side.Investigations on lifetime samples show a 2.5-fold increase in effective lifetime for surfaces passivated by an AI20a/SiNx stack compared to fully metalized AI-BSF rear sides. This low surface recombination velocity is combined with a low contact resistance.On 125 x 125 mm2 boron-doped Czochralski wafers with resistivity of 3 Ocm an efficiency of 18.6% is achieved, that is a gain of 0.7% absolute compared to the efficiency of 17.9% of the best reference cells with a full area AI-BSF. An increase in the infrared spectrum of the internal quantum efficiency is determined as the source of this gain. Also, a higher reflectance at the rear side is measured that originates most probably from the Si/AI203 interface.The quality of the rear side passivation is assessed for the metalized and non-metalized area qualitatively and quantitatively. The local rear contacts are examined via scanning electron microscopy (SE M). A contact passivation mechanism based on a local BSF formation is found that is dependent on firing conditions.

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Section: Sem Contact Area Investigationmentioning

confidence: 71%

Enabling dielectric rear side passivation for industrial mass production by developing lean printing-based solar cell processes

Lauermann

Lüder

Scholz

et al. 2010

2010 35th IEEE Photovoltaic Specialists Conference

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“…For comparison, contact resistance was also measured for screen printed and fired aluminum contacting p -silicon. Reasonable specific contact resistance of 1.4 mΩ.cm 2 and 1.8 mΩ.cm 2 was measured with sputtered aluminum on n + and p + doped silicon respectively. Contact resistance for screen printed and fired aluminum was slightly higher at 2.9 mΩ.cm 2 .…”

Section: Methodsmentioning

confidence: 99%

“…This back surface printed aluminum (Al) has relatively high back surface recombination rates [1] and sub-optimal optical reflectivity [2] compared to dielectric with point contact and it prevents the more effective utilization of longer wavelength photons. An alternative solar cell process scheme such as point contact architecture offers potentially better back surface passivation and reflectivity compared to conventional crystalline silicon solar cells [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Development of no-rinse screen printable etch paste for contact via in dielectric films

Mishra

Zhao

Zhang

et al. 2010

2010 35th IEEE Photovoltaic Specialists Conference

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Screen printable etch paste was developed for low cost patterning of dielectric films. This technique offers a simple print and bake approach to pattern without the need for a rinse step. Residue analysis of the etched area showed no sign of any organic residue left behind by the etch process. High carrier lifetime indicates no significant contamination or silicon surface damage. The etched via diameter of 150 µm was demonstrated in thermal oxide while smaller via size of 100 µm was achieved in silicon nitride (SiNx) or a combination of silicon oxide and nitride. Contact resistance measurement through the etched vias using TLM method showed values less than 3mΩ.cm 2 .The etch paste and process technique can be easily used in PERC cell as well as advanced architecture Interdigitated Back Contact (IBC) cell for low cost patterning.

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“…To avoid void formation due to a lack of Si during rapid cooling, there are several approaches. The addition of Si has already shown good results [8], [9]. In addition, the optimization of the contact spacing or firing with the Al paste on top was tested [10], [11].…”

Section: Introductionmentioning

confidence: 99%

Influence of Al Particle Size and Firing Profile on Void Formation in Rear Local Contacts of Silicon Solar Cells

Dressler

Kratt

Voss

et al. 2016

IEEE J. Photovoltaics

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Abstract-In this paper, the influence of Al particle size and the applied firing profile on void formation in local rear contacts of wafer-based silicon solar cells is investigated. Samples with a passivated emitter and rear cell (PERC) rear, but without front metallization, were metalized with six different Al screen-printing pastes, i.e., both commercial and homemade, featuring different particle size distributions and fired in a rapid thermal processing furnace with different firing profiles. Voids were detected with scanning acoustic microscopy measurements, and the fraction of voids in rear local contacts was analyzed. It was shown that the heating phase of the firing process has the strongest influence on void formation. With slower heating, void formation could be reduced to a fraction lower than 5% of the local contact area. Furthermore, it was shown that Al pastes consisting of a mixture of small and large Al particle sizes have a positive effect on the formation of voids.

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Investigation of Modified Screen-Printing Al Pastes for Local Back Surface Field Formation

Cited by 29 publications

References 4 publications

Enabling dielectric rear side passivation for industrial mass production by developing lean printing-based solar cell processes

Enabling dielectric rear side passivation for industrial mass production by developing lean printing-based solar cell processes

Development of no-rinse screen printable etch paste for contact via in dielectric films

Influence of Al Particle Size and Firing Profile on Void Formation in Rear Local Contacts of Silicon Solar Cells

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