Role of aluminum in silver paste contact to boron-doped silicon emitters

Wu, Wei; Roelofs, Katherine E.; Subramoney, Shekhar; Lloyd, K. B.; Zhang, Lei

doi:10.1063/1.4974752

Cited by 11 publications

(5 citation statements)

References 19 publications

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“…For the formation of ohmic contact on the boron-doped emitter, since the mechanism is more complicated, many attempts have been made to improve the semiconductor-metal contact. Some reports have proved that the contact resistivity between the electrode and the Si substrate could be remarkably reduced by adding aluminum particle to the Ag paste to form silver-aluminum (Ag-Al) paste [ 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. On the other hand, with the presence of the Al particle, some inappropriate Ag/Al spikes can give birth to a larger dark saturation current beneath the paste contact area [ 25 , 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

Low Recombination Firing-Through Al Paste for N-Type Solar Cell with Boron Emitter

et al. 2021

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A kind of low recombination firing-through screen-printing aluminum (Al) paste is proposed in this work to be used for a boron-diffused N-type solar cell front side metallization. A front side fire-through contact (FTC) approach has been carried out for the formation of local contacts for a front surface passivated solar cell. With a low contact resistivity (ρc) of 1.0 mΩ·cm2, good ohmic contact between the boron-doped front surface of the silicon sample and the Al paste was realized. To obtain a good energy conversion efficiency, a balance can be achieved between the open circuit voltage (Voc) and contact resistivity (ρc) of the cell by combining suitable Al powders and appropriate additives. The detailed micro-contact difference in Si/metallization between the firing-through Al paste and silver-aluminum (Ag-Al) paste was analyzed. The dark saturation current density beneath the metal contact (J0, metal) of the Si/metallization region using our firing-through Al paste was discussed, which was proven to be 61% lower than using Ag-Al paste. The pseudo energy conversion efficiency of the cell using Al paste measured by Suns-VOC was also higher than using Ag-Al paste. The role of Al paste in low surface metal recombination is discussed. The utilization of this new kind of Al paste was much cheaper and more convenient, compared to the traditional process using Ag or Ag-Al paste.

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Section: Introductionmentioning

confidence: 99%

Low Recombination Firing-Through Al Paste for N-Type Solar Cell with Boron Emitter

et al. 2021

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“…Specifically, Al is added to the Ag conductive paste to increase the contact points. The contact resistivity may be reduced about three orders of magnitude, because the silver/aluminum paste creates large and deep metal spikes [26,27]. If a high amount of Al is added to the Ag paste, the leakage currents of the solar cell increases due to large Al spikes [28].…”

Section: Introductionmentioning

confidence: 99%

“…The particle size of the aluminum powder affects the contact resistivity, which decreases with the increasing of Al particle size [26]. Wu et al [27] reported a microstructural study of the contact of the Ag/Al conductive paste with boron doped emitters, that indicated the formation of microscale metallic spikes of Al-Ag alloy and nanoscale metallic spikes of Ag-Si alloy, that allow the direct contact to the emitter.…”

Section: Introductionmentioning

confidence: 99%

Analysis of different conductive pastes to form the contact with the boron back surface field in PERT silicon solar cells

Zanesco¹,

Crestani²,

Moehlecke³

et al. 2019

Mater. Res. Express

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The industrial production of solar cells of the PERC family is growing, because the potential to increase the efficiency due to the passivation of the rear face. The PERT solar cell is a cost-effective structure of the PERC configurations. The goal of this paper is to analyze the influence in the electrical parameters of different metal pastes used to form the contact with the boron back surface field of PERT solar cells passivated with silicon dioxide on both sides and developed with a cost-effective process. The boron doped BSF and phosphorus emitter were carried out with reduction of steps. Solar cells were processed with three different conductive pastes: (1) an aluminum paste (PV381), (2) a silver/aluminum paste (PV3N1) and (3) a silver paste (PV51G), with different viscosity and solids content. The pastes were produced by DuPont. The PV381 and PV3N1 pastes produced solar cells with the efficiency of 16.2% and 15.9%, respectively. The higher open circuit voltage was achieved with the aluminum paste, indicating that this paste is more effective to produce the selective back surface field. The PV51G paste is not suitable to form the rear contact.

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“…For a front side emitter, the typical industrial metallization approach is based on screen‐printing and firing of a silver‐aluminum (Ag‐Al) paste. It has been shown that it is necessary to add a small percentage of Al to the Ag paste in order to achieve low specific contact resistances ρ C in the range of a few mΩ cm 2 . However, these Ag‐Al contacts especially trigger increased charge carrier recombination below the metallized areas leading to severe open‐circuit voltage losses and hence, energy conversion efficiency losses.…”

Section: Introductionmentioning

confidence: 99%

“…This is attributed to the lack of crystallites at the interface (e.g., Refs. report on ρ C in the range of several tens of mΩ cm 2 for Ag contacts on boron‐doped surfaces).…”

Section: Introductionmentioning

confidence: 99%

Low‐Ohmic Contacting of Laser‐Doped p‐Type Silicon Surfaces with Pure Ag Screen‐Printed and Fired Contacts

Lohmüller

Werner

Norouzi

et al. 2017

Physica Status Solidi (a)

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The state‐of‐the‐art low‐ohmic electrical contacting of highly boron‐doped silicon surfaces is based on the use of screen‐printed and fired silver‐aluminum (Ag‐Al) contacts. For these contacts, metal crystallites with depths of up to a few microns are observed at the interface. For screen‐printed and fired Ag contacts on phosphorus‐doped surfaces, the observed crystallite depths are much smaller. In this work, low‐ohmic electrical contacting of local laser‐doped p‐type silicon surfaces with commercial pure Ag screen‐printing paste are demonstrated. The doping layer is based on the “pPassDop” approach, which serves as a passivation layer on the rear side of p‐type silicon solar cells. The specific contact resistances are measured down to 1 mΩ cm2 for p‐type doping densities of about 3 × 1019 cm−3 at the silicon surface and finger widths of around 55 μm. Microstructure analysis reveals the formation of numerous small Ag crystallites at the interface with penetration depths of less than 80 nm. A first implementation of the “pPassDop” approach on 6‐inch p‐type Cz‐Si bifacial solar cells using solely Ag contacts on both sides results in a peak front side energy conversion efficiency of 19.1%, measured on a black chuck with contact bars on both sides.

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Role of aluminum in silver paste contact to boron-doped silicon emitters

Cited by 11 publications

References 19 publications

Low Recombination Firing-Through Al Paste for N-Type Solar Cell with Boron Emitter

Low Recombination Firing-Through Al Paste for N-Type Solar Cell with Boron Emitter

Analysis of different conductive pastes to form the contact with the boron back surface field in PERT silicon solar cells

Low‐Ohmic Contacting of Laser‐Doped p‐Type Silicon Surfaces with Pure Ag Screen‐Printed and Fired Contacts

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