Laser Applications in the Photovoltaic Industry

In the development and utilization of photovoltaic (PV) energy, laser technology—renowned for its high precision and efficiency—is playing an increasingly vital role. This article explores the various applications of laser technology in the PV sector and provides an outlook on its future development potential.

Laser Cutting

Laser technology is widely used for cutting crystalline silicon. By precisely controlling laser cutting parameters, manufacturers can achieve efficient and low-loss wafer slicing, thereby improving the efficiency and yield of PV modules. Laser cutting is also employed during solar cell fabrication, where laser etching enables the creation of micro- and nano-scale surface structures, enhancing light absorption and increasing cell output power.

As a highly accurate process, laser cutting is used to slice silicon solar cells into desired sizes. The basic principle involves focusing a laser beam onto the surface of the material being cut. The material absorbs the photon energy, causing localized heating. When the laser energy is sufficiently high, the material's surface is heated to a point that leads to melting or vaporization—melting for metals, and typically vaporization for non-metals like plastics or wood.

Laser Doping

Laser doping is a materials processing technique widely used in semiconductors—particularly silicon—to alter their electrical properties. The core principle involves irradiating the semiconductor surface with a high-power laser to locally melt the substrate and incorporate dopant materials (commonly boron or phosphorus) into the silicon lattice.

Key advantages include:

1. High precision: Laser doping offers excellent spatial resolution and doping control.
2. Non-contact processing: As a non-contact method, it avoids mechanical damage or contamination, making it ideal for high-performance devices.
3. High throughput: The process is fast and suitable for large-scale production.
4. Broad material compatibility: Applicable to various semiconductors, including silicon, gallium arsenide, and indium arsenide.

Laser Transfer Printing (Pattern Transfer Printing, PTP)

Laser Pattern Transfer Printing is an emerging non-contact printing technique. The principle involves coating a desired paste onto a flexible, transparent carrier, then using a high-power laser beam to selectively and rapidly transfer the paste from the carrier to the cell surface to form fine grid lines.

Key process steps include:

1. Substrate preparation: The substrate typically includes a transparent conductive oxide (TCO) layer to collect and conduct electricity.
2. Laser irradiation: A laser beam is precisely scanned over the substrate, locally sintering or patterning it to form the desired electrode structure.
3. Layer stacking: Active layers and electrodes can be transferred layer-by-layer via laser transfer.
4. Encapsulation: The final cell is formed through shaping and encapsulation.

Advantages include:

1. High precision: Capable of achieving sub-2 μm patterning with excellent uniformity—ideal for high-efficiency solar cells. Compatible with low-temperature silver paste (used in HJT cells).
2. Non-contact processing: Prevents cell damage or contamination, supporting thinner wafer technologies.
3. High-speed manufacturing: Enables rapid, high-throughput production.
4. Multi-material adaptability: Compatible with various materials including organics and silicon-based substrates.
5. Cost savings: Compared to screen printing, laser transfer enables narrower grid lines (down to 18 μm), reducing silver paste consumption by up to 30%. This is particularly advantageous for TOPCon and HJT cells using expensive silver pastes on both sides.

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Laser Drilling

Laser drilling uses high-energy-density laser beams to heat localized areas of a material to the point of melting, vaporization, or ablation, forming holes. Key parameters—such as energy density, exposure time, and focal position—must be precisely controlled to ensure accurate hole formation. Different lasers (CO₂, Nd:YAG, femtosecond, etc.) are selected based on material type and application.

In the photovoltaic sector, laser drilling has several important applications:

1. Solar cell processing: Laser drilling can form micro-holes on cell surfaces, enhancing light trapping and reducing reflection losses, thereby improving conversion efficiency. It is suitable for silicon wafers, multicrystalline cells, and other photovoltaic materials.
2. Interconnection of cells and modules: Laser drilling is used to create via holes for electrical connections between cells, ensuring smooth current flow and minimizing energy loss. It also supports structural hole fabrication for module frames and connectors.
3. Photovoltaic glass back panels: In double-glass PV modules, both the front and back panels are made of glass. The back panel requires precise hole drilling to route electrical leads to junction boxes, making laser drilling an essential process in glass deep processing.

Conclusion

Laser drilling and other laser processes play a critical role in improving solar cell efficiency, reducing manufacturing costs, and enhancing product quality. These technologies contribute significantly to the advancement of solar energy and the broader adoption of renewable energy sources.

It is worth noting that laser applications in photovoltaics extend beyond the processes mentioned above, and also include techniques such as laser grooving (e.g., for XBC cells) and laser ablation (used in PERC cell production), among others.

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