TOPCon vs Back Contact: A Fake Duel ?

Posted on: 2025/07/12

 

Intersolar 2025 marked a turning point for TOPCon technology. Many manufacturers introduced “optimized” versions of their modules, delivering up to +20 W in additional power output. These gains are the result of various technical improvements, some already deployed, others expected by the end of 2025.

 

But this boost in performance may only be a temporary response before Back Contact takes the lead.

Optimizations in “Next Gen” TOPCon

The latest TOPCon modules benefit from several key improvements :

0BB Cells and Smart Wire Technology

Visible busbars are eliminated. Instead, electrical connections are made using ultra-thin copper wires embedded in a polymer film directly laminated onto the cells.

 

  • Less shading → more light captured
  • Lower thermal stress → reduced risk of microcracks and hotspots
  • Compatible with thinner cells (reduced material usage

 
➤ Estimated gain: +5 to 8 W per module 

Post-Laser Cut Passivation

Laser cutting of half-cells degrades the passivation layer at the edges, lowering efficiency. A secondary passivation step restores electrical performance.

 

  • Reduced current losses from exposed edges

     


➤ Estimated gain: +3 to 5 W

Poly Finger

The n+ doped layer is concentrated only around the rear contact fingers, instead of being applied across the entire surface.

 

  • Fewer recombinations → better electrical performance

  • Increased bifaciality rate

     


➤ Estimated gain: +2 W and +5% bifaciality

Dual Anti-Reflective Coating

The front glass uses two stacked anti-reflective coatings (ARC) instead of one, improving light transmittance.

 

  • More efficient light capture


➤ +2.5% gain in transmittance 
➤ Power gain: significant but not precisely quantified

Optical Film for Light Redirection

A thin optical film is used to redirect incident light from inactive zones (between cells) toward active cell areas.

 

  • More effective use of incoming light


➤ Estimated gain: +3 to 5 W

Key Considerations

  • Manufacturers will not necessarily implement 100% of these improvements at once, which will lead to performance disparities across products in the same range (e.g. 1762 x 1134 TOPCon vs 2382 x 1134 TOPCon).

     

  • Most manufacturers won’t change product references; instead, they update existing IEC certifications. “High power” versions will have limited availability in Q3 and Q4 2025, resulting in two modules with the same name but different power roadmaps.

     

  • These high-performance versions are likely to come with a price adder, due to limited capacity and more expensive materials.

     

  • With this jump in nominal power, many certifications based on power output will require updates (e.g. IEC, ETN/ATEx/ATEC, ECS).

TOPCon vs Back Contact: What Can We Expect ?

With all these enhancements, TOPCon's power roadmap is beginning to overlap with Back Contact at equivalent dimensions... but perhaps only briefly.

TOPCon is nearing its theoretical efficiency ceiling (~28.7%) and is expected to plateau around 27% even with full optimizations.

 

Back Contact, on the other hand, still has significant room for improvement.

Nominal Power – TOPCon vs Back Contact Modules​ Standard Glass-Glass – 1762 x 1134 mm​

Synapsun’s Perspective :

We’re likely to see both technologies coexisting until 2026, before a probable shift in favor of Back Contact.

 

For design offices, installers, and PV buyers, this means:

 

  • Going beyond product references and analyzing datasheets carefully
  • Closely tracking manufacturer roadmaps
  • Anticipating performance variations within the same module reference
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