ADHESION and THIN-FILM M

RELIABILITY

T.J. McMahon and G.J. Jorge

National Renewable Energy Labo

Golden, CO 80401

NREL/PR-520-39842Presented at the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4) held Ma
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Outline

We measure the weakest adhesion betweevarious thin-film (T-F) modules/samples.
Outline

• We measure the weakest interlayer adhesi

of various thin-film (T-F) modules/samples. 

– An Instron mechanical testing unit is used to 

strengths at 90° or 180° on laminations of th

• before and after damp heat / UV

• and at elevated temperatures. 

– ASTM D3359 - scratch and tape pull test to 

adhesion strengths. 
Outline

• We measure the weakest interlayer adhesion be

various thin-film (T-F) modules/samples. 

– An Instron mechanical testing unit is used to mea

90° or 180° on laminations of three T-F technolog

• before and after damp heat / UV• in one instance at elevated temperatures. 

– In some cases, a scratch and tape pull test to eva

adhesion strengths. 

• Measure effect of higher temperature and relativ

adhesion/cohesion.
Outline

• We measure the weakest interlayer adhesion be

various thin-film (T-F) modules/samples. 

– An Instron mechanical testing unit is used to mea

90° or 180° on laminations of three T-F technolog

• cell contact layers to glass, • contact layers to the semiconductor, • encapsulant to cell, glass, or backsheet, etc. 

– before and after damp heat / UV– in one instance at elevated temperatures. 

– In some cases, a scratch and tape pull test to eva

adhesion strengths. 

• Effect of higher temperature and relative humidi

adhesion/cohesion.

• Adhesion’s effect on thin-film (T-F) module relia
SnO2 Delaminatio

Cause: Heat, humidity, and high vo
Bubble-type Delamin

Cause: Heat and tensile stress.
Adhesion Pull Sam
Instron Peel Test

AlignmentPlate

Substrate

Grip

Encapsulant /

Backsheet

Grip

180 °
Adhesion Strength T

Weathering 

Device: 

Source 

Failure 

Interface Time Type 

a-Si: EVA / a-Si 0 none 

A EVA / a-Si 92 h 85/85 

SiOxNy / EVA / SiOxNy 0 none  Ni paste/ Graphite/ 

CdTe: B 

SiOxNy / Ni 

paste 256 h 85/85 

3-h dry-out after removal from 85° C
Adhesion Strength T

Device: 

Source 

Failure 

Interface 

CIGS: E EVA / CIG

CIGS CIGS / MCIGS EVA / CIGCIGS Tefzel / EVCIGS Stainless / ECIGS EVA / CIGCIGS EVA / CIGCIGS Stainless / E

TPE/EVA/ EVA / Gla

Glass: F 

control EVA / Gla

EVA / Gla

TPE/EVA/ 

Glass: F 

exposed EVA / Gla

Tedlar/EVA/ EVA / Gla

Glass: G 

control EVA / Gla

EVA / Gla

Tedlar/EVA/ 

Glass: G 

exposed EVA / Gla

Scotch 

Tape/Glass Tape / Gla

ASTM 

Tape/Glass Tape / Gla

Weathering 

Device: 

Source 

Failure 

Interface Time Type 

Peel 

Strength 

(N/mm) 

a-Si: EVA / a-Si 0 none 3.8 

A EVA / a-Si 92 h 85/85 3.1 

SiOxNy / EVA / SiOxNy 0 none 5.6  Ni paste/ Graphite/ 

CdTe: B 

SiOxNy / Ni 

paste 256 h 85/85 4.5 

EVA / SiOxNy 0 none 7.0 

SiOxNy / CdTe 0 none 2.0 

SiOxNy / 

CdTe: B 

SiOxNy / CdTe 256 h 85/85 0.3 

SiOxNy / EVA / SiOxNy 0 none 6.4 

CdTe: C 

EVA / SiOxNy 256 85/85 4.9 

CdTe: C 

EVA / MetalCdTe 0 none 1.1 

CdTe: C 

EVA / MetalCdTe 256 85/85 0.6 

EVA / MetalCdTe 0 none 1.0 EVA / MetalCdTe 0 none 0.7 

CdTe: C 

(left) 

 (middle) 

 (right) Metal / CdTe 0 none 0.06 

CIGS:D1 CIGS / Mo 0 none 0.05 CIGS:D2 

60C 80C 

EVA / CIGS EVA / CIGS 

EVA cohesive 

0 0 0 

none none 

none 

7.0 1.1 

0.05 
CdTe:B cell peel te
Instron peel data: Cd

012345678

0 5 10 15 20 25 30 

Peel Extension (mm)

After 2

Dam

p 

Before

Dam

p Heat

180° Peel Strength (N/mm)
Instron peels: two Si-mo

F1, Control: 5.5 (N/mm)

G1, Control: 3.2 (N/mm)
Instron peels: two Si-mo

F1, Control: 5.5 (N/mm)F2, 7 yr UV: 2.0

G1, Control: 3.2 (N/mm)G2, 7 yr UV: 0.4
Instron peels: two Si-mo

F1, Control: 5.5 (N/mm)Plus 16h DH: 3.8F2, 7 yr UV: 2.0Plus 16h DH: 1.5

G1, Control: 3.2 (N/mm)Plus 16h DH: 1.8G2, 7 yr UV: 0.4Plus 16h DH: 0.4
CIGS:D2 De-encapsula
EVA Peel Strength vs. Te

Temperature

25°C60°C

80°C

Failure

EVA / CIGS EVA / CIGS

EVA cohesive

CIGS:D2
Bubble-type Delamin
ASTM D 3359-02 scr

CIGS:D2>7 N/mm

A lattice patinto the coasix or seven direction. Any loose frbrushed awThe ASTM qpressed firmWithin 30 to pulled back The ASTM-dwould exert N/mm on andisturbed or scratch 
ASTM D 3359-02 scr

CIGS:D2>7 N/mm

CIGS:D10.05 N/m

Tarrant, D. E.; Gay, R. R. (1995). Research on High-EfficCuInSe

2-Based Thin-Film Modules: Final Subcontract Re

16 August 1993 - 30 June 1995. 99 pp.; NREL Report No
ASTM D 3359-02 scr

a-Si:A

> 3.8 N/mm

Cd

> 5.6
Summary

• Measured interface peel strength values of 

technologies and how they are affected by esome were quite low. 
Summary

• Measured interface peel strength values of 

technologies and how they are affected by esome were quite low. 

• Adhesion at higher T and RH, and after ex

exposure show a reduction in strength.

– Minimum adhesion strength defined at higher T an– The softening of EVA near 85 °C can lead to failur
Summary

Measured interface peel strength values of technologies and how they are affected by envirwere quite low. Adhesion at higher T and RH, and after extended show a reduction in strength.A minimum adhesion strength defined at higher T and RThe softening of EVA near 85 °C can lead to failure.Achieve highest adhesion possible for corrosion anreduction.
Summary

• Measured interface peel strength values of 

technologies and how they are affected by esome were quite low. 

• Adhesion at higher T and RH, and after extended 

exposure show a reduction in strength.

– A minimum adhesion strength perhaps at higher T – The softening of EVA near 85 °C can lead to failur

• Achieve highest adhesion possible for corrosion and 

reduction.

• Interlayer adhesion in a T-F cell can be quite s

technology the ASTM D 3359-02 “Measuring Adcan be useful as a screening test.