Laser Technology in Photovoltaics Laser Processes for Solar Module Manufacturing

Lasers perform a wide range of tasks in the manufacture of crystalline silicon and thin-film modules—from drilling and patterning to welding electrical connections. Selective laser processes are also opening up new possibilities in recycling.

Lukas Remshagen is a Key Account Manager at Laserax.

The global photovoltaic market is growing at a remarkable rate. In 2023, 449 GW of capacity was installed. In 2024, this figure rose by 33 percent to 597 GW. Solar Power Europe predicts that 1 TW per year is a realistic goal starting in 2030.

China, the U.S., India, Germany, and Brazil saw the largest growth in installations. In the U.S., two-thirds of all new electricity-generating capacity to solar energy. This is partly due to increased domestic production, which rose by 190 percent compared to 2023.

Different Manufacturing Approaches for Two Types of Solar Modules

There are two main types of solar modules, each of which uses slightly different laser manufacturing techniques:

1. Crystalline Silicon Solar Cells

2. Laser Applications for Thin-Film Solar Modules

Crystalline silicon modules are the most widely used and account for about 95 percent of the global market. Production is concentrated primarily in China, where economies of scale have drastically reduced costs. These modules consist of individual silicon wafers that must be precisely joined together to form functional modules.

In contrast, thin-film modules account for only 5 percent of the global market. In the U.S., however, according to the U.S. Department of Energy, thin-film technology 17 percent of all installations and 25 percent of installations by electric utilities. Thin-film technologies such as CIGS (copper-indium-gallium-selenide) and CdTe (cadmium telluride) are produced by depositing semiconductor layers directly onto glass substrates.

These differences in structure necessitate different methods of laser processing. While the manufacturing process for crystalline silicon focuses on the preparation of individual cells and their interconnection, thin-film production requires the precise creation of structures within the layers to produce cells connected in series on a single substrate.

Laser Applications in the Manufacture of Crystalline Silicon Modules

Lasers are used at several stages in the manufacturing of crystalline silicon modules. This always requires precise control of the parameters to prevent damage to the sensitive silicon substrates.

• Laser edge isolation: Laser edge isolation removes conductive layers from the wafer edges after doping and texturing. This process prevents leakage currents that could reduce efficiency and lead to safety risks. The challenge lies in removing conductive materials from the thin silicon wafers without compromising their structural integrity.
• Laser drilling for PERC cells: Laser drilling is one of the most technically challenging applications in the manufacture of crystalline silicon modules. PERC (Passivated Emitter and Rear Cell) technology requires thousands of microscopic contact holes in the rear passivation layer. These holes typically have a diameter of 20–30 micrometers (0.0008–0.0012 inches) and must completely penetrate the passivation layer without damaging the underlying silicon substrate. This requires exceptional precision. Process windows measured in nanoseconds determine whether the holes establish the correct electrical contact or cause defects.
• Laser Scribing/Ablation: Scribing and ablation are used to fine-tune cell dimensions and create isolation trenches in the micrometer range by removing layers of materials such as silicon, transparent conductive oxides, or metallization layers. The selectivity of the laser wavelengths makes it possible to process specific materials while leaving the adjacent layers intact.
• Laser Welding of Connections: In the final step, lasers with precisely controlled wavelengths join the copper wires and busbars. This process creates strong, low-resistance electrical connections without generating excessive heat that could damage the silicon cells.

Laser Applications in the Manufacturing of Thin-Film Modules

The manufacture of thin-film modules demonstrates laser technology's ability to create complex electrical architectures through integrated processing.

The three-step engraving sequence relies on precise process control. Each laser operation builds on the previous steps to create a functional photovoltaic module.

• P1 Scribing: In the first step, structures are created in the back-side contact layer immediately after application, thereby laying the foundation for delineating the individual cells. The laser must completely remove the metallic contact on the back side without damaging the underlying glass substrate. Line widths can range from 50 to 100 micrometers (0.002 to 0.004 inches), and minimizing dead zones is a critical performance factor.
• P2 Slicing: After the absorber layer is deposited, the individual cells are isolated by removing the semiconductor material down to the back-side contact layer. This step requires a high degree of precision, as the laser must stop exactly at the interface between the absorber layer and the back-side contact layer. If the groove is cut too deep, it would damage the back-side contact layer. If it is not cut deep enough, short circuits will occur between adjacent cells.
• P3 grooving: In the final step, the front contact layer—which typically consists of a transparent, conductive oxide—is patterned using lasers. This connects the front contact of one cell to the rear contact of the adjacent cell, establishing the connection required for operation.
• Edge insulation: Next, the active layers at the outer edge are removed using lasers, which is necessary to prevent leakage currents. This process is particularly important for thin-film modules, where edge insulation is the most important mechanism for preventing ground faults due to their monolithic architecture.

Lasers in Solar Panel Recycling

As the number of end-of-life solar modules grows, their recycling is becoming increasingly important. Laser-based methods are being explored—and in some cases are already being used—to selectively separate different material layers from one another. Their main advantage lies in their non-contact and selective processing. However, a fully laser-based recycling process has not yet been economically established in all applications.

• Delamination: Lasers can locally heat or ablate encapsulation materials such as ethylene-vinyl acetate (EVA) or polyolefin elastomers (POE). This allows glass and silicon components to be separated from one another without subjecting the underlying materials to significant mechanical stress. Depending on the module design, this can enable a more precise separation than purely mechanical methods.
• Contact Removal: Laser ablation can be used to selectively remove metal contacts and coatings from crystalline silicon wafers. The goal is to cause as little damage as possible to the underlying silicon, thereby facilitating further material recycling.
• Glass Cleaning: Even residual polymer and adhesive residues can be removed from glass substrates using laser techniques. This allows the glass to be prepared for further recycling or reuse processes without having to rely exclusively on chemical or abrasive cleaning methods.
• Recycling of thin-film modules: In thin-film modules, lasers can selectively ablate individual semiconductor layers, such as cadmium telluride or CIGS, while the glass substrate remains largely intact. Such processes could help in the future to recover valuable materials in a more targeted manner and reduce the use of chemical separation processes.

The Key Benefits of Laser Technology in Solar Manufacturing

Laser technology plays a key role in every phase of solar production, helping to streamline manufacturing and improve yields. Here are just a few of the benefits.

• Precision and Efficiency: Lasers are highly precise and enable high-density interconnection patterns and effective use of the active area. Laser texturing can create microscopic surface structures that reduce reflection and increase light absorption. This enables higher power output. These surface modifications can improve cell efficiency.
• A recent study shows efficiency gains of up to 0.22 percent. That may not seem like much, but given the global sales volume of solar modules, it really adds up.
• Improved Light Absorption: Laser-generated surface structures improve photon absorption in solar cells, particularly in thin-film applications, since the length of the absorption paths is limited. This also reduces energy loss by isolating the current paths.
• Scalability: Non-contact processing enables high-throughput production without concerns about mechanical wear or tool changes. This speeds up production cycles and avoids frequent interruptions for maintenance or replacement.
• Consistent results: The precisely controlled energy input remains constant, which improves quality and ensures consistent results even for large print runs.

Promoting Growth in the Solar Industry

Laser processes perform a variety of tasks in the manufacturing and, increasingly, the recycling of solar modules. Their strengths lie in particular in precise, non-contact, and selective processing. At the same time, new cell architectures and materials are placing greater demands on process control. Lasers can enable targeted energy input without unnecessarily stressing adjacent structures. 

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