Download - WS 2012 T13 Frankfurt 04 Kajari-Schroeder
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack statistic of
crystalline silicon
photovoltaic modules
S. Kajari-Schrder, I. Kunze,
F. Haase, M. Kntges
Institute for Solar Energy
Research Hamelin
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Inactive cell area
Why analyze cracking of cells? Cell cracks in PV modules can lead
to electrically separated cell area
fractions after artificial aging
For 230W module with 60 cells: separated cell area fraction of 8%
or more leads to significant
reduction of module power
M. Kntges, I. Kunze, S. Kajari-Schrder, X. Breitenmoser, B. Bjrneklett, Sol.
Energy Mater. Sol. Cells (2011), doi:10.1016/j.solmat.2010.10.034
200 Humidity-
freeze cycles
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack classification
no crack dendritic several
directions +45 -45
parallel
to busbar
perpend.
to busbar
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack statistics Different load histories
Transport
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Experimental as delivered 103 PV modules 60 cells
(15.6 cm), multicrystalline
From various manufacturers
Max. 5 PV modules/package
Inflict cracks to cells in PV module only by production or
transport
Determine local crack distribution in EL image
Production
Transport
EL
Exemplary image, not analyzed
transport
M. Kntges, S. Kajari-Schrder, I. Kunze, U. Jahn,
Proc. 26th EUPVSEC (WIP, Hamburg, Germany, 2011) 4EO.3.6
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Lateral crack distribution As delivered
High breakage rate in center Moderate breakage rate
near frame
Low breakage rate in corners
Symmetry to increase statistical significance
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
As delivered
Lateral crack distribution
High breakage rate in center Moderate breakage rate
near frame
Low breakage rate in corners
Symmetry to increase statistical significance
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
PV modules show non-homogeneous crack distribution Distribution correlates with strain distribution of 1st eigenmode 45crack in corners does not correlate Tensile strain promotes crack growth
Noise reduction utilizing symmetries
Lateral crack distribution
Dendritic
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack statistics Different load histories
Field
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Measurement in the field 574 PV modules (multi cryst.) with FL method
M. Kntges, S. Kajari-Schrder, I. Kunze, SOPHIA Workshop PV Module
Reliability, May 4-3 2012, Lago di Lugano (Switzerland)
Exemplary image, not
the analyzed field
4CO.11.4
Exemplary image, not analyzed field
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Lateral crack distribution
PV modules show non-homogeneous crack distribution Distribution correlates with strain distribution of 1st eigenmode Tensile strain promotes crack growth Parallel to busbar more often than tensile strain suggests
Dendritic
Noise reduction utilizing symmetries
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack statistics Different load histories
Uniform mechanical load
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Uniform mechanical load
27 PV modules 60 cells (15.6 cm)
Multi & mono crystalline cells
From various manufacturers
Inflict cracks to cells in PV module by mechanical load test 5400 Pa
Determine crack distribution in EL image analysis
Flash/EL
Mechanical
load test 5400 Pa
Flash/EL
S. Kajari-Schrder, I. Kunze, U. Eitner, M. Kntges, Sol. Energy Mater. Sol. Cells
(2011),doi: 10.1016/j.solmat.2011.06.032
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Lateral crack distribution
PV modules show non homogenous crack distribution Distribution correlates with strain distribution of load simulation 45 crack in corners is higher than expected Tensile strain promotes crack growth
Cracked cells [%] Dentritic cracks [%] Serveral directions [%]
R/C 1 2 3 4 5 R/C 1 2 3 4 5 R/C 1 2 3 4 5Cells per module: 60
1 59 37 44 38 36 1 5 1 2 2 3 1 6 2 3 3 1Number of modules: 27
2 27 52 53 46 46 2 9 9 6 6 10 2 5 9 10 4 1Cracked cells per module[%]: 41,2
3 31 31 40 35 43 3 11 4 8 6 10 3 8 6 14 6 11Cracked cells per module[#]: 24,7
Parallel to Busbar [%] Perpendicular to Busbar [%] 45 cracks [%] Simulation pressure 5400 Pa
R/C 1 2 3 4 5 R/C 1 2 3 4 5 R/C 1 2 3 4 5
1 0 19 35 32 32 1 0 0 0 0 0 1 48 15 4 0 0
2 1 18 30 33 33 2 1 0 0 0 0 2 10 16 6 3 1
3 4 12 15 22 21 3 6 0 0 0 0 3 1 5 11 1 0
R/C 1 2 3 4 5
1
2
3
Dendritic
Noise reduction utilizing symmetries
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack statistics Different load histories
Comparison
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Different load histories compared
Transport Field Uniform mec. load
Busbars in: long direction short direction long direction Relative amount of cracked cells:
Transport: 5.74 %
Field: 4.15 %
Uniform: 41.2 %
Cracks are ubiquitous
Dendritic cracks more dominant in artificial
crack initiation
Cracks perpendicular to busbars are rare
Dendritic
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Risk of cell part separation in
artificial aging
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Separated cell area
Definition of the potentially
separated cell area:
Area that is limited by a crack or the
border of the cell and that has no
functional metal finger to the busbar
Different crack orientations have
different worst case separated cell
areas
different potential impact on module power output
Crack
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Experimental
PV modules with 60 15.6x15.6 cm
mono & multi crystalline cells Power Measurement
Electroluminescence
Mechanical load test
(5400 Pa)
200 humidity freeze
cycles
Initiation of cracks into the cells in the PV modules with mechanical load test (IEC
61215)
Stressing of the cells by 200 humidity freeze cycles (similar to IEC 61215)
Power Measurement
Electroluminescence
Power Measurement
Electroluminescence
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Potentially separated cell area all crack orientations
30 % of the cracked cells show less than 8 %
potentially separated cell
area
Low risk for power losses
11 % of the cracked cells show more than 25 %
potentially separated cell
area
High risk for power losses
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack orientation dependence
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Cracks parallel to the busbars shows peak between 16 24 % potentially separated cell area
Diagonally cracked cells mostly have lower potentially separated
cell areas
Crack orientation dependence
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Experimental
PV modules with 60 15.6x15.6 cm
mono & multi crystalline cells Power Measurement
Electroluminescence
Mechanical load test
(5400 Pa)
200 humidity freeze
cycles
Initiation of cracks into the cells in the PV modules with mechanical load test (IEC
61215)
Stressing of the cells by 200 humidity freeze cycles (similar to IEC 61215)
Power Measurement
Electroluminescence
Power Measurement
Electroluminescence
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Crack type definition EL Image @ Isc
EL Image @ 1/10 Isc
A A
A No resistance across crack
B B
B Degraded, still connected, but increased resistance
C C
C Isolated, inactive cell area
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Isolated cell area after artificial aging
C
Correlation of potentially separated cell area due
to crack orientation and
electrically isolated cell
area after aging
7 % of the cracked cells develop isolated cell
parts
Isolated cell area of up to 17 %
iso
late
d
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
B
Correlation of potentially separated cell area due
to crack orientation and
electrically degraded
cell area after aging
29 % of the cracked cells degrade in artificial
aging
Degraded cell areas of up to 34 %
Degraded cell area after artificial aging
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
B Cracks partially not
detected before aging
Correlation of potentially separated cell area due
to crack orientation and
electrically degraded
cell area after aging
29 % of the cracked cells degrade in artificial
aging
Degraded cell areas of up to 34 %
Degraded cell area after artificial aging
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Isolation and degradation of
different crack orientations
Relative probability for electrically isolated cell
area independent of crack
orientation
Cells with several crack orientations and cracks
parallel to the busbars
degrade most often
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Summary Cracks are ubiquitous
Cracks distribution depends on load history
Cracks parallel to the busbars are most frequent and can separate large cell
areas
29 % of cracked cells degrade in aging
Funding was provided by the State of Lower Saxony and BMU under
contract number 0325194C TASK13
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IEA INTERNATIONAL ENERGY AGENCY
PHOTOVOLTAIC POWER SYSTEMS PROGRAMME
Advanced technologies and materials for
crystalline Si solar cells and modules
March 25 - 27, 2013 Hamelin, Germany
Scientific topics:
Junction formation Surface morphology and passivation Cleaning and etching Structuring and contact formation Silicon material Wafering and kerfless technologies Advanced characterization and simulation Process integration Module integration Reliability
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