Extending the limits of screen-printed metallization of phosphorus- and boron-doped surfaces

Werner, Sabrina; Lohmüller, Elmar; Aßmus, W.; Clement, Florian

doi:10.1016/j.solmat.2016.05.064

Cited by 24 publications

(12 citation statements)

References 25 publications

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“…Despite the very similar surface concentration ( N max = 5 × 10 20 cm −3 ), the investigations reveal a reasonably low ρ c = (10 ± 0.5) mΩ cm 2 for a silver paste on an alkaline textured surface with the R sh of the highly doped area of SE with 50 Ω/sq prepared by a larger pulse‐energy density ranging from 1.5–1.7 J/cm 2 , and ρ c = (8 ± 1) mΩ cm 2 for a silver paste on an alkaline‐textured surface with a R sh of the highly doped area of SE with 70 Ω/sq prepared by a larger pulse‐energy density ranging from 1.3 to 1.4 J/cm 2 . A lower ρ c exists for an R sh of the highly doped area of SE with 70 Ω/sq; thus, N max determines the ρ c value of highly doped emitters and the Ag paste influences the electrical contact formation …”

Section: Resultsmentioning

confidence: 99%

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Zhang

Zheng

et al. 2018

Progress in Photovoltaics

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We report that the application of a laser‐doped selective emitter (SE) can improve the trade‐off between the recombination in the emitter and the Ag‐Si specific contact resistance and that a double‐screen‐printed rear aluminum grid can decrease the series resistance in the industrial bifacial passivated emitter and rear cell (PERC). Our results reveal that a front‐side efficiency of 21.9% can be achieved in the PERC (SE)+ solar cell by using low surface‐recombination Al2O3/SiNx films as passivation layers, low‐recombination emitter, and low resistive Ag‐Si contact with an optimized sheet resistance of the lightly doped area of SE with 125Ω/sq and sheet resistance of the highly doped area of SE with 70 Ω/sq. The highest front‐side efficiency of 22.0%, with open‐circuit voltage of 680 mV, short‐circuit current density of 40.1 mA/cm2, and fill factors of 80.8%, is obtained by using double‐screen‐printed rear Al grid process, which is 0.1% higher than the best PERC (SE)+ solar cell. The rear‐side double‐layer antireflection coating consists of 50 nm SiNx:H (n = 2.1) and 10 nm SiNx:H (n = 2.37), which enables a large bifacial gain with the output power density PMPP of 25.5 mW/cm2 in the PERC (SE)+ solar cell by using double‐screen‐printed rear Al grid process when rear‐side illumination intensity Erear = 0.25 suns.

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Section: Resultsmentioning

confidence: 99%

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Zhang

Zheng

et al. 2018

Progress in Photovoltaics

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“…Both processes result in 4 · 10 19 cm −3 < N max < 5 · 10 19 cm −3 and a profile depth d prof ≈ 400 nm. Both profiles show the depletion at the surface which is typical for BBr 3 diffusion processes with in‐situ oxidation …”

Section: Overview Of the Settings Used For Laser Doping From The Glasmentioning

confidence: 90%

“…For bifacial n‐type silicon solar cells with front side boron emitter, it has been shown that the charge carrier recombination within the passivated emitter area can be drastically reduced by lowering the maximum charge carrier concentration N max . On the other hand, low specific contact resistance in the range of a few mΩcm 2 is maintained for screen‐printed silver–aluminum (Ag–Al) contacts . However, such lowly‐doped emitters show increased local charge carrier recombination at the Ag–Al contacts of several thousand fA cm −2 which lead to severe open‐circuit voltage losses .…”

Section: Overview Of the Settings Used For Laser Doping From The Glasmentioning

confidence: 99%

“…Approach : Phosphorus‐doped n‐type Czochralski‐grown silicon wafers with an edge length of 156 mm and a base resistivity ρ Base ≈ 2.6 Ω cm (determined after thermal donor annihilation) are either saw damage etched or alkaline textured prior to the BBr 3 diffusion processes that are performed in an industrial tube furnace. We investigate two BBr 3 diffusion processes, both of which feature a short in‐situ oxidation . The reference process is referred to as “Ref”.…”

Section: Overview Of the Settings Used For Laser Doping From The Glasmentioning

confidence: 99%

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Advanced BBr₃ Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping

Lohmüller

2018

Physica Rapid Research Ltrs

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The concept of attaching a second deposition step at the end of boron tribromide (BBr3) diffusion is introduced, where second deposition describes an active nitrogen flow through the BBr3 bubbler. This approach provides a higher boron dose in the borosilicate glass (BSG) which facilitates the formation of laser‐doped selective emitters. It is found that the second deposition hardly impacts the as‐diffused charge carrier concentration profile in comparison to BBr3 diffusion without second deposition. The emitter sheet resistance Rsh ≈ 110 Ω sq−1 and emitter dark saturation current density j0e ≈ 25 fA cm−2 (alkaline textured, Al2O3/SiNX passivation) are similar for both processes. The BBr3 diffusion process forms a BSG/silicon dioxide (SiO2) stack layer on the silicon. The BBr3 diffusion with second deposition step results in an 8 nm thicker BSG/SiO2 stack layer (total thickness: 42 nm) with factor two higher boron dose compared to the BBr3 diffusion without second deposition. After laser doping, the charge carrier concentration is higher for the BBr3 process with second deposition resulting in stronger local doping with about 10 Ω sq−1 lower Rsh. For laser‐doped and Al2O3/SiNX‐passivated areas, a promising process combination results in j0e = (250 ± 30) fA cm−2 at Rsh = (65 ± 1) Ω sq−1.

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“…In the near past, the dynamic progress of screen‐printing Ag pastes enabled the electrical contacting of phosphorus‐doped surfaces with N surf down to a few 10 19 cm −3 with ρ C < 8 mΩ cm 2 . These improvements revived the approach to use pure Ag pastes (without Al) for contacting 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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Extending the limits of screen-printed metallization of phosphorus- and boron-doped surfaces

Cited by 24 publications

References 25 publications

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Advanced BBr₃ Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping

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

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Extending the limits of screen-printed metallization of phosphorus- and boron-doped surfaces

Cited by 24 publications

References 25 publications

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Efficiency enhancement of bifacial PERC solar cells with laser‐doped selective emitter and double‐screen‐printed Al grid

Advanced BBr3 Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping

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

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Product

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Advanced BBr₃ Diffusion With Second Deposition Step for Selective Emitter Formation by Laser Doping