The document discusses the evolution and current trends in backsheet design for photovoltaic modules, focusing on the need for high-performance materials that provide mechanical protection, electrical insulation, and moisture resistance. Key trends include the use of innovative materials, adhesive-less construction, and the design of backsheets that enhance module efficiency and reflectivity. The presentation concludes with a call for specifically engineered films to replace traditional materials, promoting a greener manufacturing process.

1. Current Trends
in
Backsheet Evolution
Prepared and presented by:
Marina Temchenko
R&D Manager
Madico, Inc.
March 2012

2. Presentation Outline
1. Backsheet history
2. Current trends in Backsheet design
3. Backsheet contribution to module performance
4. New Technologies
5. Conclusions

3. Backsheet History
The backsheet is an outer layer of the module;
Often a highly engineered, multi-layered structure.
Required performance properties:
1. Mechanical protection
2. Electrical insulation
3. Water/Moisture vapor resistance
4. Solvent resistance
5. UV stability
6. Adherence to encapsulant
7. Adherence to sealants, labels, etc
8. Thermal stability
9. Dimensional stability
10. Flame retardancy
11. Compatibility with module
components

4. Backsheets History
From Tedlar to New Materials
Alternative Process Methods
designs
Protekt® Coating/Polyester/EVA
Technical designs
Performance
Evolution
Alternative Coatings
Tedlar®/Polyester/EVA (fluorinated or non)/
designs PE/Other?
Tedlar®/Polyester/Tedlar® designs
designs
All Polyester
designs
Madico Patent
circa 2005
Time

5. Current Trend:
Superior Cost Performance

6. The Holistic Design Process
Creativity/Innovation/Action
1. It begins with the outer Weather-able Layer:
Composition Choice: A) Inherently weather-able polymers, or
B) Additive-compounded polymers
Thickness Choice: A) Commercially available films
B) Precision Coating
2. Next in the chain is the Inner Layer:
Current design
1. Polyethylene terephtalate: A) Hydrolytically unstable
B) Cost
2. Polyamides
3. Polyolefins
4. Others
Sequential Logic is the
3. The third building block: the interior Outer Layer: key to Innovative
Composition Choice: A) Degree of Reflectivity Backsheet Design!
B) Thermal Conductivity
C) Compliment to Module Design
1. For Bi-facial Modules
2. For back-contact cells

7. Weather-able Layer:
Composition Choice
The
Smart 1. Inherently weather-able polymers Bond strength
Choice! a. Fluoropolymers 488 kJ/mol
2. Additive-compounded polymers
a. Wide range of base resins – all rely on the Bond strength
presence, performance, and durability of 348 kJ/mol
additives
*International Union of Pure and Applied Chemistry (1994). "Bond dissociation energy"
Compendium of Chemical Terminology
(Internet edition)

8. Weather-able Layer:
Precise Thickness

9. Weather-able Layer:
Durability and material selection
Product 1
Product 2

10. Interior Outer Layer
(Adjacent to the encapsulant)
Performance Requirements:
1. Excellent adhesion to the encapsulant
2. Low moisture vapor transmission
3. Good dielectric properties
4. Increased reflectivity
5. Enhanced thermal conductivity

11. Interior Outer Layer
(Adjacent to the encapsulant)
Differential Performance Measures:
1. Reflectivity!
Increased reflectivity results in higher PV module
power output
79.2
Pmax vs.
79
Reflectance
78.8 y = 0.0189x + 76.523
78.6
78.4
R2 = 0.9863
Pmax (W)
78.2
78
77.8
77.6
60 65 70 75 80 85 90 95
Reflectance (%)

12. Interior Outer Layer
(Adjacent to the encapsulant)
Differential Performance Measures:
1. Reflectivity
2. Sustained Reflectivity over module
performance life
Product 1
Product 2

13. Current Trend
Adhesive-less construction
Possibilities:
• Coating/PET/Coating
• Coating/PET/extruded layer
Possible Benefits:
• “Greener” manufacturing process – less VOC
• Elimination of weak link – an adhesive

14. Adhesive-less construction
Product 1
Product 2

15. Compliment PV Module Designs
Bifacial Solar Cells
• Converts the sunlight
incident on both sides
of the modules
• Increase module
efficiency by 3-4%
• Requires transparent
backsheet

16. Transparent Backsheets

17. Transparent Backsheets

18. Conclusion
1. High performance Low cost backsheets
2. Specifically designed films or coatings for PV
applications, replacing off the shelf pre-engineered
films
3. Adhesiveless construction
4. Compliment Module Design

19. Special thanks to the contributors of this presentation
Amy Schweighardt
Andrea Jones
Brad Forest
Dave Avison
Katrina Sampson
Robert Comeau
Sam Lim
Shreyans Shingi
Tony Lim
Venkatesh Natarajan

20. Questions?