Busbar

What is a busbar

A busbar is a thin metallic strip on the front surface of a solar cell that collects the electrical current generated by the cell and conducts it to the next cell in the series-connected string. The busbar is typically silver paste printed onto the cell during manufacturing, then soldered to interconnect ribbons that link cells together.

Solar cell evolution has progressively reduced busbar shading. Early cells used 2-3 wide busbars; mainstream cells moved to 4-5 medium busbars; modern cells use 9-12 thin busbars (multi-busbar, MBB) or even more (16BB). Newest designs eliminate busbars entirely (0BB) by soldering thin wires directly to the cell metallisation.

The Indian solar industry follows global busbar trends. Modern ALMM-listed modules predominantly use 9BB to 12BB designs. 0BB and SmartWire technologies are emerging in premium and HJT cells.

Why busbars matter

Cell efficiency. Reducing busbar width and number improves module efficiency by 1-3 percent, which lets residential rooftop solar design fit more wattage into the same roof footprint.

Current collection. Lower resistance in distribution of current to module terminals, without altering per-cell voltage.

Reliability. Better busbar adhesion reduces interconnect failure.

Manufacturing cost. Silver paste consumption is a major cost driver.

Bifacial performance. Rear-side metallisation affects the rear-side power captured by bifacial modules.

Busbar evolution

Technical deep dive

Why more busbars are better

MBB cell efficiency gain

Going from 5BB to 9BB to 12BB typically delivers:

• 5BB to 9BB: +0.5 to 0.8% efficiency
• 9BB to 12BB: +0.2 to 0.3% efficiency
• 12BB to 16BB: +0.1 to 0.2% efficiency

Diminishing returns at higher busbar counts.

Comparison with shingled cell

Shingled cell uses overlapping cell strips without traditional busbars. Higher density and efficiency but more complex manufacturing. Rear-contact designs such as IBC cells take a different approach again, moving all contacts to the back of the cell so the front carries no busbars at all.

Soldering and ribbon

Interconnect ribbons solder to cell busbars. Modern designs use multiple thinner ribbons per cell matching busbar count, reducing series resistance and improving thermal expansion compatibility with the surrounding encapsulant.

Real-world applications

All crystalline silicon solar cells.

MBB: dominant in 2024-2026 ALMM-listed modules.

0BB and SmartWire: premium and HJT cells.

Advantages of MBB

Higher cell efficiency.

Lower hot spot risk.

Better current distribution.

Improved reliability.

Compatible with half-cut and bifacial.

Limitations

Diminishing returns above 12 busbars.

Manufacturing complexity at very high counts.

Limited gain on HJT (already low resistance).

Common busbar problems

Cell crack at busbar from thermal stress.

Soldering defect on busbar.

Discolouration of busbar over years.

Reduced contact at busbar-ribbon interface.

Indian market context

Indian ALMM-listed modules predominantly 9BB-12BB.

Major manufacturers (Waaree, Adani Green Solar, Vikram, Tata Power Solar) ship MBB modules across monocrystalline PERC and TOPCon platforms, the same module choices weighed in Solar Inverter for a 3 BHK Home, Real Sizing and Best Picks when a roof-constrained residential system needs higher-wattage panels.

0BB and SmartWire entering premium Indian segment.

PM Surya Ghar accepts MBB modules that clear the ALMM list requirements for subsidy disbursement.

Standards and certifications

Key takeaways

Busbars collect current from solar cells and conduct it to module terminals. Modern multi-busbar (MBB) designs with 9-16 thin busbars deliver 1-3 percent efficiency gain over older 3-5 busbar designs. Indian ALMM-listed modules are predominantly 9BB-12BB. Emerging zero-busbar and SmartWire technologies offer further gains in premium and HJT cells. Busbar evolution is one of the steady contributors to solar cost reduction.

Further reading

For how Busbar plays out in real projects, these guides go deeper:

• Inverter Battery Connection Diagram and Sizing Guide for Hybrid Solar
• Inverter MPPT: 8 Critical Selection Factors (2026)
• Polysun Review 2026: Multi-Energy System Simulation, Assessed
• ALMM List-II Exemption Window for Net Metering & Open Access

Sources

• IEC 61215, Module qualification.
• IEC 61730, Module safety.
• IS 14286, Indian module standard.
• ITRPV Roadmap, latest edition.
• Manufacturer documentation from major module brands.
• IEA PVPS Trends 2024.
• NREL Best Research-Cell Efficiency Chart.
• Meyer Burger SmartWire documentation.
• Trina, JinkoSolar, LONGi MBB technical papers.