What is anti-reflective coating?
Anti-reflective coating (ARC) is a thin layer applied to solar cells (and increasingly to module glass) that reduces the amount of incoming sunlight reflected away. Untreated silicon reflects about 30 percent of incident light. With a well-designed ARC, this drops to under 10 percent. The additional light absorbed by the cells contributes directly to module efficiency, making ARC an essential feature on all modern silicon solar cells.
Silicon nitride is the dominant ARC material for crystalline silicon cells. The coating is deposited via plasma-enhanced chemical vapour deposition (PECVD) during cell manufacturing. The coating's thickness and refractive index are tuned to minimise reflection across the solar spectrum. The characteristic blue or dark colour of solar cells comes from the ARC; untreated silicon would appear gray.
Beyond cell-level ARC, modern premium modules also apply anti-reflective coating to the front glass. This reduces reflection at the glass surface, adding another 2 to 3 percent of light transmission. Combined with cell ARC, the result is modules that reflect only a few percent of incoming sunlight.
Why ARC matters
For module efficiency, ARC is one of the foundational technologies that makes commercial silicon solar viable. Without ARC, silicon module efficiency would be several percentage points lower, materially affecting payback economics.
For premium product differentiation, AR-coated glass modules deliver 2 to 3 percent additional yield over standard-glass modules. The premium pays back in higher cumulative generation.
For bifacial modules, ARC is applied to both faces of the cells to maximise both front-side and rear-side generation.
For policy and standards, ARC is implicitly required through module efficiency thresholds in ALMM listings.
Benefits of ARC
- Reduced reflection. From 30 percent to under 10 percent at cell level.
- Higher efficiency. Multiple percentage points of absolute efficiency gain.
- Standard on commercial cells. Universal feature of modern solar.
- Glass-level ARC option. Additional efficiency gain for premium modules.
- Bifacial-friendly. Both cell faces can be ARC-coated.
- Stable long-term. Cell ARC protected by EVA and glass.
- Tuneable. Can be optimised for specific spectral ranges.
Limitations
Soiling masks ARC benefit. Dust on the surface reduces transmission.
Glass ARC durability. Long-term weathering can degrade glass ARC slightly.
Cost. Adds some manufacturing cost; minimal relative to module total.
Cannot eliminate reflection entirely. Some loss remains.
Wavelength tuning. Cannot optimise for all wavelengths equally.
ARC in Indian modules
| Aspect | Detail |
|---|---|
| Cell-level ARC material | Silicon nitride (Si3N4) dominant |
| Coating method | PECVD (plasma-enhanced chemical vapour deposition) |
| Cell appearance with ARC | Blue or dark blue/black |
| Glass ARC in premium modules | Common in TOPCon, HJT, premium PERC |
| Combined reflection reduction | Total module reflection a few percent |
| Standards | Implicit in module efficiency thresholds |
| Bifacial modules | ARC on both cell faces |
Quick facts
| Term | Anti-Reflective Coating (ARC) |
|---|---|
| Function | Reduces reflection from cell and module surfaces |
| Cell ARC material | Silicon nitride (typical) |
| Without ARC reflection | ~30 percent |
| With ARC reflection | Under 10 percent |
| Glass ARC additional | 2 to 3 percent transmission gain |
| Coating method | PECVD for cell ARC |
| Status | Universal on modern silicon cells |
Common mistakes about ARC
- Assuming all cells have identical ARC. Quality and tuning vary.
- Confusing cell ARC with glass ARC. Different applications.
- Treating ARC as a maintenance item. No user maintenance needed.
- Forgetting that soiling masks ARC benefit. Cleaning matters.
- Skipping glass ARC in premium evaluations. Adds meaningful yield.
- Treating black cells as "no ARC". Black cells often have additional treatments alongside ARC.
Key takeaways
- ARC reduces light reflection from solar cells and module glass.
- Without ARC, silicon reflects about 30 percent of light; with ARC, under 10 percent.
- Silicon nitride is the dominant cell-level ARC material.
- The characteristic dark blue cell colour comes from ARC.
- Premium modules apply ARC to module glass too, adding 2 to 3 percent transmission.
- Bifacial modules have ARC on both cell faces.
- ARC is universal on modern commercial silicon solar cells.
Frequently Asked Questions
What is anti-reflective coating in solar?
Anti-reflective coating (ARC) is a thin layer applied to solar cells (and sometimes module glass) that reduces the reflection of incoming sunlight. Less reflection means more light absorbed by the cells, improving efficiency. ARC is standard on all modern silicon solar cells, typically appearing as the dark blue or black colour of the cell surface.
How much does ARC improve efficiency?
Without ARC, silicon cells would reflect about 30 percent of incoming light. With well-designed ARC, reflection drops to under 10 percent. The efficiency gain from ARC is several absolute percentage points, making it essential for commercial solar.
Why are solar cells blue or black?
The dark colour comes from the anti-reflective coating. Untreated silicon is gray. The ARC layer is tuned to reflect a small range of wavelengths (typically appearing blue) while transmitting the rest of the solar spectrum into the cell. Black-appearing cells often have additional surface treatments.
What material is used for ARC?
Silicon nitride (Si3N4) is the dominant ARC material for crystalline silicon cells. Titanium dioxide and silicon dioxide are also used in some designs. The choice depends on cell architecture and desired anti-reflective properties.
Is ARC applied to module glass too?
Yes increasingly. Anti-reflective coating on the module's front glass reduces reflection losses at the glass surface, adding another 2 to 3 percent of light transmission. Module glass ARC is common in premium modules.
How is ARC applied?
Cell-level ARC is typically deposited via plasma-enhanced chemical vapour deposition (PECVD) during cell manufacturing. Module glass ARC is applied by various coating processes during glass production.
Does ARC degrade over time?
Cell-level ARC inside the module is protected by EVA and glass; it does not degrade meaningfully. Module glass ARC can be slightly affected by long-term weather but typically retains most function over 25 years.
Is ARC affected by soiling?
Soiling on the module surface reduces light transmission regardless of ARC. Cleaning restores function. ARC does not protect against soiling.
What is the difference between ARC on cells vs glass?
Cell-level ARC reduces silicon surface reflection. Glass-level ARC reduces glass surface reflection. Both add efficiency; together they reduce total module reflection losses to a few percent.
Are anti-reflective glass modules more expensive?
Slightly. AR-coated glass adds modest cost. For high-volume modules, ARC glass is often standard. For utility-scale and premium residential, ARC glass is typically included.
How does ARC interact with bifacial modules?
Both faces of bifacial modules need ARC: front-side cell ARC for primary generation and rear-side cell ARC for back-side bifacial generation. Quality bifacial modules apply ARC to both cell faces.
Does ARC work in low-light conditions?
Yes. ARC reduces reflection at all irradiance levels. The proportional benefit is the same; the absolute energy gain is higher when irradiance is higher.
Run your solar business on QuickEstimate
India's mobile-first solar CRM. Send subsidy-ready proposals on WhatsApp in 60 seconds. Free for 10 proposals a month, no card.
Start free →Sources
- NREL. Anti-reflective coating research. nrel.gov
- Fraunhofer ISE. Surface texturing and ARC studies.
- IEC 61215. Module qualification testing.
- Cell manufacturer technical references. ARC specifications.
- ITRPV roadmap. ARC technology evolution.
- Glass manufacturer publications. Module glass ARC.
- IS 14286. Indian module standard.
Written by QuickEstimate Editorial, QuickEstimate Editorial (Surat).
Last updated: 4 June 2026.