What Is EVA?

What is EVA?

EVA, Ethylene Vinyl Acetate, is the transparent thermoplastic polymer used as the encapsulant inside solar modules. Sheets of EVA sit between the tempered glass front and the cells, and between the cells and the polymer backsheet (or rear glass in bifacial designs). During vacuum lamination at about 150 degrees Celsius, the EVA melts, cross-links chemically, and bonds with the glass, cells, and backsheet to create a sealed, weatherproof package.

EVA has been the standard module encapsulant for decades because of a useful combination of properties: high optical transparency (so light reaches the cells), good adhesion to multiple surfaces, electrical insulation, weatherproofing, and reasonable cost. The polymer is typically about 0.5 mm thick per layer, with two layers per module.

POE (polyolefin elastomer) is the main alternative, used increasingly in bifacial glass-glass modules and some premium products. POE has lower moisture transmission, better PID resistance, and less long-term yellowing than EVA. EVA remains dominant in mainstream Indian modules because of cost.

Why EVA matters

For module performance, EVA quality affects light transmission to cells and long-term resistance to degradation. Quality EVA with UV stabilisation maintains transparency over 25 years; poor EVA yellows and reduces module output over time.

For module reliability, EVA's adhesion and moisture resistance protect cells from environmental damage. Delamination or moisture ingress is among the failure modes that can shorten module life.

For manufacturing, EVA is one of the bills-of-material items that affect both cost and quality. Tier-1 manufacturers source EVA from established suppliers with consistent specifications.

For policy, encapsulant standards are part of IEC 61215 qualification testing, which BIS-aligned IS 14286 incorporates.

How EVA functions in a module

1. Layup. Glass + EVA sheet + cells + EVA sheet + backsheet assembled in stack.
2. Vacuum lamination. Stack placed in laminator; heated to about 150 degrees Celsius under vacuum.
3. EVA melts. Thermoplastic becomes flowable, filling gaps around cells.
4. Cross-linking. Chemical cross-linking transforms EVA from thermoplastic to thermoset.
5. Cooling. Module cooled while pressed; final adhesive bonds set.
6. Sealed package. Cells now encapsulated and sealed.
7. Light transmission. Sunlight passes through glass and EVA to cells.
8. Moisture protection. EVA blocks water ingress through the module.
9. Field operation. EVA degrades slowly over decades.

Benefits of EVA

• High light transparency. Light reaches cells efficiently.
• Strong adhesion. Bonds to glass, cells, backsheet.
• Moisture protection. Blocks water ingress.
• Electrical insulation. Safe operating environment.
• Cost-effective. Lower than alternatives.
• Well-understood manufacturing. Decades of lamination experience.
• Standards-aligned. Meets IEC 61215 requirements.

Limitations

Long-term yellowing. UV exposure can discolour EVA over decades.

Moisture transmission. Higher than POE.

PID susceptibility. Higher than POE in some cell architectures.

Delamination risk. Possible in extreme conditions.

Recycling complexity. Hard to separate from glass and cells.

EVA in Indian modules

Aspect	Detail
Dominant encapsulant	EVA in mainstream Indian PERC and TOPCon modules
Premium alternative	POE in some glass-glass bifacial
Standards	IEC 61215, IS 14286
Typical thickness	0.5 mm per layer, 1 mm total
Lamination temperature	About 150 °C
Suppliers	Specialty polymer manufacturers globally

Quick facts

Full form	Ethylene Vinyl Acetate
Function	Module encapsulant sealing cells between glass and backsheet
Thickness	0.5 mm per layer, 1 mm total typical
Process	Vacuum lamination at ~150 °C
Alternatives	POE (polyolefin elastomer)
Key properties	Transparency, adhesion, moisture barrier, electrical insulation
Field life	25+ years with quality EVA

Common mistakes about EVA

1. Treating EVA quality as identical across manufacturers. Tier matters.
2. Ignoring UV stabilisation specification. Affects long-term yellowing.
3. Confusing EVA with POE. Different polymers, different properties.
4. Skipping encapsulant in module evaluation. Affects long-term reliability.
5. Assuming all bifacial use POE. Some use EVA.

Key takeaways

• EVA is the standard encapsulant in commercial solar modules.
• Seals cells between glass front and backsheet (or rear glass).
• Applied by vacuum lamination at about 150 °C.
• Quality EVA maintains transparency over 25-year module life.
• POE is the premium alternative, growing in bifacial glass-glass modules.
• Standards: IEC 61215, IS 14286.
• Encapsulant quality contributes to long-term module reliability.

Frequently Asked Questions

Sources

• IEC 61215. Module qualification testing including encapsulant evaluation.
• Fraunhofer ISE. Encapsulant research and POE vs EVA comparisons.
• NREL. Module materials and degradation studies. nrel.gov
• Module manufacturer datasheets. Encapsulant specifications.
• ITRPV roadmap. Encapsulant market trends.
• Industry whitepapers. EVA vs POE technical comparisons.
• IS 14286. Indian module standard.