Solar cell process development in the European Integrated Project CrystalClear

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Solar cell process development in the European
Integrated Project CrystalClear
R. Russel,
I. Romijn, A. Weeber,

• G. Beaucarne, J. John, P. Choulat, Y. Ma,

M. Hofmann, R. Preu,
A. Slaoui,
N. Le Quang, O. Nichiporuk,
C. del Cañizo, A. Pan,
H. Nagel, J. Horzel,
H. Solheim, J. Evju,
B. Bitnar, M. Heemeier, T. Weber,
B. Raabe, H. Haverkamp, C. Strümpel, J. Junge, S.
Riegel, S. Seren, G. Hahn
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Outline

• What is CrystalClear ?
• What is done on solar cell development within
  CrystalClear ?
• What has been achieved ? (Highlights)
• Is an Integrated Project dealing with process
  development a good idea ?

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CC project structure and research topics
Total budget 28 M (16 M EC contribution, 12 M
partners contribution) Project duration 5 years
(1 Jan 2004 31 Dec 2008)
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SP4 Goals

• Develop designs and manufacturing processes to
  enable a 40 cost reduction at cell level
• Focus on
• Low Cost Materials
• Thin Wafers

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Cell process Subproject at a glance
High efficiency on low cost material
Novel processesfor thin substrates
Photon conversion for Si cells enhancement
High efficiencymanufacturing
Ultra-thin wafers
Inline characterization
Advanced cell designs
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Investigation of up-converters
Applying various up-converters to bifacial solar
cells
Strümpel et al. 1DV.2.17, Thursday
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Cell process Subproject at a glance
High efficiency on low cost material
Novel processesfor thin substrates
Photon conversion for Si cells enhancement
High efficiencymanufacturing
Ultra-thin wafers
Inline characterization
Advanced cell designs
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High efficiency solar cells on Si ribbons
EFG
36.8 mA/cm2 632 mV 78.1 18.2 (2 x 2 cm2)
Kaes et al., Milan conference Junge et
al., 2CV.4.69, Wedn.
RGS
Grain size 0.2 mm 30.6 mA/cm2 596 mV 79.1 14.4
(2 x 2 cm2)
RGS mainly limited by intragrain quality !
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Cell process Subproject at a glance
High efficiency on low cost material
Novel processesfor thin substrates
Photon conversion for Si cells enhancement
High efficiencymanufacturing
Ultra-thin wafers
Inline characterization
Advanced cell designs
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High efficiency large-areamulticrystalline Si
cells

• full aluminium BSF
• laser grooved buried contacts
• texturing by mechanical grooving

Joint achievement with other EC project TOPSICLE
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Focus industrially applicablerear structures
with low recombination

• e.g. a-Si/SiOx in combination with Laser Fired
  Contacts
• Confirmed efficiency 21.7 on 4cm² FZ (250µm)

Hofmann et al. Dresden conference
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Very thin solar cells with B-BSF
Cz, p-type, 1.5 Wcm,125² mm²
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Very thin multi Si cells with dielectric rear
passivation

• Industrial-type PERC cell (i-PERC)

• Plasma texturing
• Passivating stack deposited oxide/SiNx
• Local Al-alloying for Al-BSF

120 mm thick mc-Si
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Study of wafer strength forintentionally cracked
very thin mc-Si wafers
Gustafsson, 2DV.1.37, today Larsson, 2DV.1.38,
today
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Cell process Subproject at a glance
High efficiency on low cost material
Novel processesfor thin substrates
Photon conversion for Si cells enhancement
High efficiencymanufacturing
Ultra-thin wafers
Inline characterization
Advanced cell designs
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Solar cells with MWT structure and rear
dielectric passivation with fired-through contacts

• Rear side passivated PUM cell ASPIRe
• ASPIRe All Sides Passivated and Interconnected
  at the Rear
• Specific silicon nitride developed for the rear
• Firing through screenprinted Al metallization at
  the rear
• 16.4 efficiency achieved with ASPIRe (180 µm
  thick multi, 243 cm2)

Romijn, Mewe et al. 2AO.1.4, Monday
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Cell process Subproject at a glance
High efficiency on low cost material
Novel processesfor thin substrates
Photon conversion for Si cells enhancement
High efficiencymanufacturing
Ultra-thin wafers
Inline characterization
Advanced cell designs
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Processing ultra-thin monocrystalline Si
substrates

• 17.3 screenprinted cells down to 100µm thick
  100cm² Cz-Si
• 16.6 achieved on 80 µm thick 4 inch Cz-Si (35.6
  mA/cm2, 632 mV)

Y. Ma et al., 2DO.3.2, This afternoon
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Cell process Subproject at a glance
High efficiency on low cost material
Novel processesfor thin substrates
Photon conversion for Si cells enhancement
High efficiencymanufacturing
Ultra-thin wafers
Inline characterization
Advanced cell designs
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High speed illuminated lock-in thermography
Thermography tests
iLIT in Voc conditions at 1 Hz - Edge shunt
visible even after 1s
Intensity lt 1 sun
Even lower intensity
iLIT in Voc conditions at 1 Hz - Al
contamination at front side visible
Seren et al. 2CV.5.52, Wednesday
Lowering of frequency lowering of intensity ?
detection of shunts possible within 1 s
measurement time ? iLIT suitable for in-line
measurements !
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Using broad consortium for useful tests

• Example Round robin on IV measurements
• Idea Test of IV measurements at partners using
  identical cells
• Work Independent measurements, at the end
  calibrated measurements at CalLab
• Goal Determine accuracy of measurements,
  improve precision of IV measurement

Hahn et al. 2DO.2.6 This afternoon
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Cell process Subproject at a glance
High efficiency on low cost material
Novel processesfor thin substrates
Photon conversion for Si cells enhancement
High efficiencymanufacturing
Ultra-thin wafers
Inline characterization
Advanced cell designs
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Joint companies-institutes experiments on large
batches
Ex.1
Alkaline texture
at Deutsche Cell
POCl3 diffusion
P glass etching
PECVD SiN deposition
One Side Etching
Cleaning
BS Passivation (PECVD)
15nm SiO2 (thermal)
ARC Deposition
at Fraunhofer ISE
Pad Paste Printing
Al Paste Printing
Ag Paste Printing Fine line
Hofmann et al. 2CV.5.37 Wednesday
Paste Co-Firing
Laser fired contact
Silver Plating
Tempering
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Was an Integrated Project a good idea?

• Learning process from competition to
  collaboration
• Growing sense of community
• Advantages
• provides framework to carry out new joint
  experiments in short timeframe
• yearly replanning gives useful flexibility and
  possibility to focus
• Integrated Projects complementary to other
  project forms

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Summary

• CrystalClear involves a large volume of RD on
  solar cell processing
• Leading edge results have been achieved,
  particularly with industrial cells on very thin
  wafers and with ribbons
• CrystalClear is a powerful vehicle for
  collaboration and communication between partners
  in the EU

After the conference, this paper will be
downloadable from the CrystalClear website
www.ipcrystalclear.info
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• Acknowledgements
• Thanks to CrystalClear coordinator, Project
  Management Office and Executive Board for
  excellent work and trust
• Thanks to Sub-Project Alumni Guido Agostinelli,
  Kristian Peter, Peter Fath, Eric Rüland and
  others for their contributions
• Thanks to European Commission for financial
  support

After the conference, this paper will be
downloadable from the CrystalClear website
www.ipcrystalclear.info