Silicon diffusion in aluminum for rear passivated solar cells

Urrejola, Elías; Kingshott, Peter; Plagwitz, Heiko; Schubert, Gunnar

doi:10.1063/1.3579541

Cited by 60 publications

(42 citation statements)

References 15 publications

(18 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Si diffuses much faster into the Al/Si alloy (through the necks between sintered Al particles) than Al diffuses in the opposite direction toward the local contacts. As the cooling is very fast (∼5 s), it may occur that Si solidifies as lamellas in the Al particles, instead of recrystallizing in the local contact area, and voids are formed [5]. To avoid void formation due to a lack of Si during rapid cooling, there are several approaches.…”

Section: Introductionmentioning

confidence: 99%

“…Frequently, a formation of voids in local rear contacts is observed [5], [6] resulting in some cases in a non-BSF passivated local contact or no local contact to the rear-side metallization at all. One of the hypotheses regarding void formation is that voids are formed due to the Kirkendall effect [7].…”

Section: Introductionmentioning

confidence: 99%

“…As the dissolved Si darkens the paste, this can be measw-ed by meru1s of optical microscope images. The width of the darkened AJ paste is called the maximum spread limit of Si in the AI paste [5]. Subsequentl y, the paste pmticles and the eutectic layers were etched off in hydrochloric acid sol uti on, and the deptb of the local contacts, not considering tbe remaining BSF, was measured, also using optical microscope images.…”

mentioning

confidence: 99%

See 2 more Smart Citations

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

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

show abstract

“…A well-known problem of the PERC concept is the formation of voids in the rear local contacts [4], [5]. The Kirkendall effect [6] is a good explanation for the void formation, as Si diffuses much faster in Al than Al in Si [4].…”

Section: Introductionmentioning

confidence: 99%

“…By adding only a few process steps, cell efficiencies more than 21% on large-area (15.6 × 15.6 cm 2 ) Czochralski (Cz) monocrystalline Si solar cells have been reached [2], [3]. A well-known problem of the PERC concept is the formation of voids in the rear local contacts [4], [5]. The Kirkendall effect [6] is a good explanation for the void formation, as Si diffuses much faster in Al than Al in Si [4].…”

Section: Introductionmentioning

confidence: 99%

Nondestructive Characterization of Voids in Rear Local Contacts of PERC-Type Solar Cells

Dressler

Rauer

Kaloudis

et al. 2015

IEEE J. Photovoltaics

View full text Add to dashboard Cite

Abstract-In this paper, we present two nondestructive characterization methods for the detection of voids in rear local contacts of passivated emitter and rear-type solar cells, namely scanning acoustic microscopy and computer tomography. We compare both methods and include a comparison with electroluminescence measurements. It is shown in this paper that voids can easily be detected with both measurement types without any sample preparation. We found a good match of scanning acoustic microscopy (SAM) and computer tomography (CT), which is presented for this purpose for the first time. The investigation was carried out for different aluminum pastes.Index Terms-Computer tomography (CT), crystalline silicon, passivated emitter and rear cell concept (PERC), scanning acoustic microscopy (SAM), solar cells, voids.

show abstract

Diffusion-based model of local Al back surface field formation for industrial passivated emitter and rear cell solar cells

Lauermann

Fröhlich

Hahn

et al. 2013

Prog. Photovolt: Res. Appl.

View full text Add to dashboard Cite

In this work, the back surface field (BSF) formation of locally alloyed Al‐paste contacts employed in recent industrial passivated emitter and rear cell solar cell designs is discussed. A predictive model for resulting local BSF thickness and doping profile is proposed that is based on the time‐dependent Si distribution in the molten Al paste during the firing step. Diffusion of Si in liquid Al away from the contact points is identified as the main differentiator to a full‐area Al‐BSF; therefore, a diffusion‐based solution to the involved differential equation is pursued. Data on the Si distribution in the Al and the resulting BSF structures are experimentally obtained by firing samples with different metal contact geometries, peak temperature times and pastes as well as by investigating them by means of scanning electron microscopy and energy dispersive X‐ray spectroscopy. The Si diffusivity in the Al paste is then calculated from these results. It is found that the diffusivity is strongly dependent on the paste composition. Furthermore, the local BSF doping profiles and thicknesses resulting from different contact geometries and paste parameters are calculated from the Si concentration at the contact sites, the diffusivity and solubility data. These profiles are then used in a finite element device simulator to evaluate their performance on solar cell level. With this approach, a beneficial paste composition for any given rear contact geometry can be determined. Two line widths are investigated, and the effects of the different paste properties are discussed in the light of the solar cell results obtained by simulation. Copyright © 2013 John Wiley & Sons, Ltd.

show abstract

Silicon diffusion in aluminum for rear passivated solar cells

Cited by 60 publications

References 15 publications

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

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

Nondestructive Characterization of Voids in Rear Local Contacts of PERC-Type Solar Cells

Diffusion-based model of local Al back surface field formation for industrial passivated emitter and rear cell solar cells

Contact Info

Product

Resources

About