holistic reliability program – adhesion and module ... · holistic reliability ... in long-term...
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Mason Terry, PhD- Sunnyvale, CA USA
DuPont Photovoltaic & Advanced Materials
Holistic Reliability
Accelerated Testing of Metallization Adhesion
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2
DuPont Photovoltaic Solutions Portfolio
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• Evaluate durability for PV materials and
their interactions and synergies in module
• Provide science-based understanding of
materials-related lifetime performance
• Develop test protocols that predict field
exposure performance
• Develop products with highest durability
to deliver more power output throughout the
life of the module
Holistic Cell and Module Durability
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• Infant-failure occurs in the beginning of the working life of a PV module.
• IEC testing useful for infant and short-term failure detection.
• Questionable if IEC testing will predict midlife to end of life failure.
IEA International Energy Agency, PVPS report T13-01:2014
The Usual IEC Testing Graph
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Extended Qualification Stress Testing Shortcomings
Current accelerated tests do not adequately predict performance in the field
– Power loss mechanism is different from the field
– e.g. Hydrolysis damage of backsheets occurring beyond DH1000 is not
observed in the field
Power Loss
UV, Humidity Freeze
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Risk of Low-Laydown Architectures
Modern low-laydown structures might pose risk for durability
Ag laydown reduction over time • Cells from
4-5 yr. ago
• Module
reliability
field data
begins to
emerge
• Cells from
today
• No field
module
reliability
data yet
Goals:
• Determine critical limit to durability for laydown
• Deliver cost-saving metallization architectures, while excluding compromises
in long-term stability
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Variation of paste-driven adhesion component
Results:
Vary busbar thickness; fingers constant:
Busbar thickness does not impact
performance
Wide adhesive force range: 0.3 – 3N/mm!
Is there an impact on module durability?
+
=
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
5 10 15 20
Avg
Ad
he
sio
n (
N/m
m)
Busbar thickness (um)
Ma
xim
um
ad
he
siv
e fo
rce
(N
/mm
)
Busbar-tabbing Ribbon Adhesion
Method:
Double print:
Print thickness variation busbar screens
and soft bake.
Print same finger screen.
Same firing conditions.
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Paste-driven adhesion and durability
Humidity Freeze (3x TC50-HF10)
Maximum adhesive force (N/mm)
Thermal Cycling (TC-250x)
Maximum adhesive force (N/mm)
Damp Heat 1000 hours
Maximum adhesive force (N/mm)
Humidity Freeze (3x TC50-HF10)
Paste-driven adhesion does not affect module durability under IEC testing
Busbar-Tabbing Ribbon Adhesion
IEC Based Stress Testing
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DuPont pastes meet all adhesion criteria
Adhesion of >1 N/mm is safe for durability under IEC conditions tested
Adhesion of all DuPont pastes is >2.5 N/mm
Adhesion safe for durability under conditions tested
Reasonable Lower Limit
Paste
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Accelerated Adhesion Testing Development
With the reduction in laydown by >70%, what is the impact on
adhesion for long term module reliability?
No test currently exists to test long term adhesion.
Goal:
• Develop a simple cost effective accelerated test to determine long term
adhesion durability.
Method:
• Borrow an accelerated test method from Microelectronics industry to determine
long term adhesion durability.
• Bake tabbed cells at 850C and 1200C for 0, 50 and 100 hours, followed by
temperature cycling from -400C to 850C for 50 cycles.
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Tests currently
being carried out
to add HF10 after
TC50 and
includes PV19B
paste
Little to no change in adhesion or Pmpp from baking at either
temperature followed with TC50!
Accelerated Adhesion Testing Results
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DuPont™ Solamet® product development includes accelerated testing
to failure to identify composition differences
- DH and PCT tests produce similar ordering and PCT is 10X faster
PCT conditions: 120°C, 1.98 bar
Test-to-Failure PCT and DH Exposure PCT 600 hrs
DH 6000 hrs
PCT Conditions 120oC, 100%RH
1.98 Bar
DH Conditions
85oC, 85%%RH
1 Bar
IEC
Qualification
Test-1000 hrs
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Summary
• Continued price reductions have led to dramatic changes in solar panel
materials and designs such as low-laydown architectures which may pose
risks to durability and reliability
• Paste-driven adhesion does not affect module durability under IEC testing
range from 0.3 to 3 N/mm.
• Aged adhesion testing using 85C and 120C, followed by TC50, shows
negligible adhesion and Pmpp loss for DuPont™ Solamet® pastes.
• New Solamet® PV19x is designed for improved aged bonding strength
even under extreme conditions of 150C for 100 hours
• PCT test to failure 10X faster than DH with very similar results
• Choice of materials significantly impacts solar panel performance and cost
of ownership- Materials Matter™
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Copyright © 2016 DuPont. All rights reserved. The DuPont Oval Logo, DuPont™, Materials Matter™, and all products denoted with ® or ™ are registered trademarks or trademarks of E.I. du Pont de Nemours and Company or its affiliates.
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