holistic reliability program – adhesion and module ... · holistic reliability ... in long-term...

Mason Terry, PhD- Sunnyvale, CA USA

DuPont Photovoltaic & Advanced Materials

Holistic Reliability

Accelerated Testing of Metallization Adhesion

2 Copyright © DuPont 2016. All rights reserved.

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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)


Damp Heat 1000 hours


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™


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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holistic reliability program – adhesion and module ... · holistic reliability ... in long-term...

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