Coherent broadens PV presence

SANTA CLARA, CA—Last week Hamburg, Germany hosted the 24th European Photovoltaic Solar Energy Conference and Exhibition (EUPVSEC)—one of the most important annual events for suppliers of photovoltaic processing equipment (see page 2). Laser-maker Coherent took the opportunity to announce a broader presence in the photovoltaic (PV) marketplace by introducing two new turnkey process tools for use in crystalline-silicon (c-Si) solar-cell manufacturing production.

This product release marks a move by Coherent up the equipment supply chain—instead of supplying “just lasers,” it aims to offer turnkey laser-based wafer handling and processing tools for the PV production line, says Finlay Colville, Coherent’s director of marketing, solar. Colville notes that Coherent’s lasers have been used in both c-Si and thin-film photovoltaic production for at least five years so the company is already known in the PV field. The new products will broaden its penetration of the PV equipment market.

Two platforms were announced, one aimed at early stage R&D for evaluation of a range of different laser-based processes with the other designed specifically for high-throughput operation. The R&D tool—named Aethon—offers a combination of high-speed beam-scanning optics and software-controlled wafer positioning hardware and diagnostics. The high-throughput Coherent Equinox tool can be configured for qualification of laser-based processes prior to full production line implementation or optimized for high-throughput production line capability at up to several thousand wafers per hour.

Applications for lasers in solar-cell processing including c-Si edge isolation, dielectric ablation, dopant diffusion, laser-grooved buried contacts, wrap-through, and texturing. According to the Coherent brochure for its new laser-based tools, lasers offer non-contact micro-materials processing with feature sizes at the micron-level, while performing selective material modification and removal. Laser-based tools operate with negligible utility requirement and consumables, reducing operating costs.

Within the past couple of years, several high-efficiency cell concepts have moved from R&D to pilot-line production, as the push to realizing mass-produced 20% efficiency ‘standard’ cells was accelerated. These new cell types involve different manufacturing steps, compared to the traditional method of producing c-Si cells. And within these are a range of new laser process steps during front and back contact (metallization) stages. With more stringent demands now placed upon both laser and laser-based tools, a wider range of laser types is needed to maintain process quality levels and low cost of ownership. With optimized parameters including shorter ultraviolet (UV) wavelengths (355 nm and lower), sub-nanosecond-pulsewidths (at the ‘picosecond’ level), and high average power levels of tens to hundreds of Watts, the AVIA laser was joined by other Coherent solutions such as the Talisker, Paladin, and Excimer laser product lines. As such, a new family of c-Si ‘solar-specific’ lasers is available within the Coherent product portfolio.