Characteristics of busbarless connection

Busbarless (0BB/ZBB) connections eliminate front-side busbars on solar cells, using fine gridlines and ribbons to collect current, improving efficiency and reducing material costs.

Overview

Busbars are metallic lines on solar cells that collect and transport electrical current. Traditional cells use multiple busbars (2BB to 21BB) to reduce series resistance, but they occupy surface area, causing shading and reducing light absorption. Busbarless technology, also called 0BB or ZBB, removes these busbars entirely.

Instead, ribbons or wires collect current directly from the fine gridlines, which reduces shading, improves the cell-to-module (CTM) efficiency, and lowers silver usage by 30–50% per cell.

Electrical and Mechanical Considerations

Without busbars, contacting the fine gridlines becomes more complex. Each grid finger must be individually contacted, often requiring independent current and voltage contacts to minimize resistive losses and ensure accurate performance measurement. Techniques include: Wire-embedded EVA sheets: Cells are laminated with SnBiAg wires embedded in EVA, achieving low contact resistivity and high efficiency (~19.

55%) at optimized lamination temperatures. Electrically Conductive Adhesives (ECA): Pads of ECA are applied to each finger, decoupling electrical contact from mechanical adhesion. This allows optimization of both conductivity and adhesion while reducing material usage.

Metal connecting wires: In busbar-free modules, metal wires are soldered to the cell gridlines, simplifying alignment and reducing the risk of unstable connections.

Advantages

Higher Efficiency: Less shading from busbars increases light absorption and improves CTM ratio. Material Savings: Reduced silver paste usage lowers production costs. Compatibility with Thin Wafers: Flexible connection methods allow the use of thinner silicon wafers, further reducing costs.

Enhanced Stability: Multiple contact points reduce losses from microcracks and improve module reliability.

Applications

Busbarless technology is compatible with advanced solar cell types such as HJT (Heterojunction), TOPCon (Tunnel Oxide Passivated Contact), and back-contact cells, making it a versatile solution for high-efficiency PV modules. Industrial adoption has been growing, with mass production of 0BB cells already underway in leading PV manufacturers.

Summary

Busbarless connections represent a significant evolution in solar PV technology. By eliminating busbars and using fine gridlines with ribbons or conductive adhesives, they enhance efficiency, reduce material costs, and improve module stability, while requiring careful design of electrical contacts and lamination processes to maintain performance. This technology is central to modern high-efficiency solar modules and is increasingly adopted in commercial production.