A Roadmap Toward 24% Efficient PERC Solar Cells in Industrial Mass Production

Min, Byungsul; Müller, M.; Wagner, Hannes; Fischer, Gerd; Brendel, Rolf; Altermatt, Pietro P.; Neuhaus, Holger

doi:10.1109/jphotov.2017.2749007

Cited by 117 publications

(67 citation statements)

References 39 publications

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“…On the other hand, the plan view and cross‐sectional SEM images for the contact holes at each step made by the modified LFC process are shown in Figure . At the first step, for the purpose of breaking only the passivation layers with minimal damage to Si, the subthreshold number of laser pulses at a 10.3 J/cm fluence, which is slightly lower than that in the conventional LFC process (10.9 J/cm 2 ), was irradiated. The cross‐sectional view SEM image in Figure A reveals the passivation layers are opened leaving a small amount of Al on the local contact.…”

Section: Resultsmentioning

confidence: 99%

“…The efficiency of industrial passivated emitter and rear cell ( i ‐PERC) has been increasing steadily and reaching over 22% . It is expected that efficiency will increase up to 24% by introducing selective emitter, stronger rear local back surface field (LBSF), and advanced front grid design . Although Al back surface field (BSF) solar cells account for more than 60% of the total market in 2018, the demand of the PERC cells in the market is expected to increase gradually and will dominate the market share in the near‐term future …”

Section: Introductionmentioning

confidence: 99%

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Modified laser‐fired contact process for efficient PERC solar cells

Choi

Jung

Park

et al. 2019

Progress in Photovoltaics

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A laser‐fired contact (LFC) process is one of the techniques for making local electrical contacts at the rear side of passivated emitter and rear cell (PERC) solar cells. In the LFC process, opening of the passivated dielectric layers and alloying of Si and Al need to be made in a single step laser process. For this reason, the LFC process is accompanied by the loss of Al and the laser damage to the Si wafer. In this study, we present a novel multistep LFC process combining the conventional LFC and laser‐induced forward transfer (LIFT) processes. The modified LFC scheme we proposed consists of three steps: (a) opening of the passivation layers and partial alloying of Al‐Si, (b) additional deposition of Al on the local contact holes, and (c) post laser firing of the transferred Al. Applying the modified LFC process to the PERC cells of 1.0 cm2 of area, we demonstrate the effective recombination velocity of the laser‐processed wafers can be remarkably reduced while maintaining the low contact resistance. The best of the PERC solar cell fabricated by the modified LFC process exhibited an efficiency of 19.5% while the conventional LFC‐PERC cell showed 18.6%. The efficiency gains of the modified LFC‐PERC cells was largely contributed by the enhanced open circuit voltage (Voc) and fill factor (FF).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modified laser‐fired contact process for efficient PERC solar cells

Choi

Jung

Park

et al. 2019

Progress in Photovoltaics

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“…Since the Toledo modules were manufactured, Si PV module efficiencies have increased considerably through the use of a rear passivation layer with localised contacts. This passivated emitter and rear cell (PERC) design, which was first reported by Blakers et al, is now being manufactured in increasing volumes in China . The reduced recombination current density in these cells makes them more sensitive to impurities in the Si such as B‐O defects and metal impurities.…”

Section: Challenges For Copper‐plated Silicon Solar Cellsmentioning

confidence: 99%

“…Reports of light‐induced degradation (LID) due to the B‐O defects raised the importance of this problem with numerous subsequent reports seeking to elucidate the mechanisms of the B‐O complex formation and deactivation through thermal treatments under carrier injection conditions . The ability to mitigate the effects of the light‐induced (also referred to as carrier‐induced) B‐O defect became more critical with the projected greater market share of commercially‐produced PERC cells, as these more efficient cells are more sensitive to bulk recombination. Light‐induced degradation due to B‐O complexes also raised questions about the role of carrier concentration in altering the recombination properties of other impurity‐related complexes and, in doing so, has re‐energised investigations into the contribution of metal impurities to recombination in Si solar cells.…”

Section: Challenges For Copper‐plated Silicon Solar Cellsmentioning

confidence: 99%

“…Furthermore, the smaller contact areas achieved by lasers for plated contacts require higher aspect ratio conductors with a smaller interface area for adhesion, which can present potential additional challenges with respect to module reliability (see Section 2.2.2). One approach to reducing contact recombination is to use a SE, where the surface under the metal contact is more heavily‐doped . Copper‐plated metallisation has been demonstrated with solderable p‐type SE PERC cells; however, achievement of the SE required additional patterning steps to either form the SE or form anchor points in laser‐doped regions to provide sufficient adhesion for soldered interconnection …”

Section: Challenges For Copper‐plated Silicon Solar Cellsmentioning

confidence: 99%

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Challenges facing copper‐plated metallisation for silicon photovoltaics: Insights from integrated circuit technology development

Lennon

Colwell

Rodbell

2018

Progress in Photovoltaics

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Copper‐plated interconnects were widely adopted for volume manufacture of integrated circuits after more than a decade of intensive research to demonstrate that use of Cu would not impact device reliability. However, although Cu‐plated metallisation promises significantly reduced costs for Si photovoltaics, its adoption in manufacturing has not gained the same traction. This review identifies some key challenges facing the introduction of Cu‐plated metallisation for Si photovoltaics. These include the following: (1) increased carrier recombination due to the use of Cu for metal contact formation; (2) reduced module reliability due to adhesion or contact integrity failures; and (3) limited availability of cost‐effective processes and equipment for metal plating. For integrated circuits, Cu's low electrical resistance and high resistance to electromigration provided an impetus for the large investment in process development that was required to realise Cu‐plated interconnects. However, the technical advantages of using Cu for Si solar cell contacts are not as compelling, as solar cells can tolerate larger feature sizes thus reducing the criticality of the contact metal's conductivity and electromigration properties. Additionally, for Si photovoltaics, low cost is paramount, and new challenges arise from the need for modules to absorb light and operate in the field for 25+ years in diverse outdoor climates. However, with the scale of Si photovoltaic manufacturing expected to increase dramatically in the next decade, the use of large quantities of silver for cell metallisation will provide an incentive to address reliability concerns regarding the use of Cu for Si photovoltaic metallisation.

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