Current Trends in Backsheet Evolution

Prepared and presented by:

Marina TemchenkoR&D ManagerMadico, Inc.March 2012

Presentation Outline

1. Backsheet history

2. Current trends in Backsheet design

3. Backsheet contribution to module performance

4. New Technologies

5. Conclusions

Backsheet History

Required performance properties:

1. Mechanical protection2. Electrical insulation3. Water/Moisture vapor resistance4. Solvent resistance5. UV stability6. Adherence to encapsulant7. Adherence to sealants, labels, etc8. Thermal stability9. Dimensional stability10. Flame retardancy11. Compatibility with module

components

The backsheet is an outer layer of the module; Often a highly engineered, multi-layered structure.

Backsheets HistoryFrom Tedlar to New Materials

Tedlar®/Polyester/Tedlar®designs

TechnicalPerformanceEvolution

Time

Tedlar®/Polyester/EVAdesigns

Madico Patentcirca 2005

All Polyesterdesigns

Protekt® Coating/Polyester/EVAdesigns

Alternative Coatings(fluorinated or non)/

PE/Other?designs

Alternative Process Methodsdesigns

Current Trend: Superior Cost Performance

The Holistic Design ProcessCreativity/Innovation/Action

Sequential Logic is the key to Innovative Backsheet Design!

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:

3. The third building block: the interior Outer Layer:

Composition Choice: A) Degree of Reflectivity B) Thermal Conductivity

C) Compliment to Module Design

1. For Bi-facial Modules

2. For back-contact cells

1. Polyethylene terephtalate: A) Hydrolytically unstable B) Cost

Current design

2. Polyamides

3. Polyolefins

4. Others

Weather-able Layer: Composition Choice

1. Inherently weather-able polymersa. Fluoropolymers

2. Additive-compounded polymersa. Wide range of base resins – all rely on the

presence, performance, and durability of additives

*International Union of Pure and Applied Chemistry (1994). "Bond dissociation energy"Compendium of Chemical Terminology (Internet edition)

Bond strength488 kJ/mol

Bond strength348 kJ/mol

TheSmart Choice!

Weather-able Layer:Precise Thickness

Weather-able Layer: Durability and material selection

Product 1Product 2

Interior Outer Layer (Adjacent to the encapsulant)

Performance Requirements:

1. Excellent adhesion to the encapsulant2. Low moisture vapor transmission3. Good dielectric properties4. Increased reflectivity5. Enhanced thermal conductivity

Interior Outer Layer (Adjacent to the encapsulant)

Differential Performance Measures:1. Reflectivity!

Increased reflectivity results in higher PV module power output

Pmax vs. Reflectance

y = 0.0189x + 76.523

R2 = 0.9863

77.6

77.8

78

78.2

78.4

78.6

78.8

79

79.2

60 65 70 75 80 85 90 95Reflectance (%)

Pm

ax (

W)

Interior Outer Layer (Adjacent to the encapsulant)

Differential Performance Measures:1. Reflectivity 2. Sustained Reflectivity over module

performance life

Product 1Product 2

Current TrendAdhesive-less construction

Possibilities:• Coating/PET/Coating• Coating/PET/extruded layer

Possible Benefits:• “Greener” manufacturing process – less VOC• Elimination of weak link – an adhesive

Adhesive-less construction

Product 1 Product 2

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

Transparent Backsheets

Transparent Backsheets

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

Amy Schweighardt Andrea JonesBrad Forest Dave Avison Katrina SampsonRobert ComeauSam Lim Shreyans ShingiTony LimVenkatesh Natarajan

Special thanks to the contributors of this presentation

Questions?