This year’s EU PVSEC exhibition was notable for the plethora of new production tools and processes for next-generation crystalline-silicon production lines, as suppliers respond to cell manufacturers’ prioritization of high-efficiency cell concepts. It’s a great example of how market dynamics drive technology innovation, especially when supply exceeds demand by a considerable margin, observes Coherent’s Finlay Colville.
by Finlay Colville, Coherent Inc.
September 29, 2009 – With the current slowdown in capacity expansions from most crystalline-silicon (c-Si) manufacturers, the equipment supply chain to the sector has reacted strongly by increasing the range of tool options and cell concepts in alignment with high-efficiency c-Si cells demanded for long-term competitiveness.
While equipment suppliers eagerly await the widespread transition from standard (c-Si) cell production to high-efficiency cell concepts, the 24th European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) in Hamburg, Germany (9/21-9/25) did not disappoint. Anyone doing a quick side-by-side comparison with last year’s exhibition in Valencia may well have been left scratching their head, trying to account for the plethora of new production tools and processes being marketed for next-generation c-Si production lines. So, let’s explain how this has come about, why it’s actually great news for the industry as a whole, and then look at what might happen next as a result.
Two converging themes explain the background to the range of new production equipment shown in Hamburg. First is the relentless stream of research activity toward next-generation c-Si cell concepts, which today is dominated in number by the European research institutes and ongoing local collaborative projects. The other factor is a shift in supply/demand dynamics within the industry over the past 12-18 months — i.e., moving from a seller’s to a buyer’s market. At previous equipment exhibitions, tooling on display tended to meet legacy demand from cell manufacturers for ongoing capacity expansion of moderate-efficiency standard c-Si cell types. Now, with c-Si cell capacity expansion this year considerably reduced, EU PVSEC was dominated by next-generation technologies targeting the anticipated capacity expansions from 2011 onwards — where c-Si cells will begin to reflect the concepts best championed within the research community. Without a doubt, market dynamics drive technology innovation — especially when supply exceeds demand by a considerable margin.
The days of moderate-efficiency and high-cost c-Si cells seem to be over. Polysilicon pricing aside, c-Si cell production is now moving rapidly toward high-efficiency territory previously the domain only of premium high-bulk-quality back-junction or HIT c-Si cell types. Low-cost tooling (both fixed and operating costs) for cell lines appears less visible, perhaps driven more in-house by cell producers than from the equipment supply-chain itself. Inherent to each high-efficiency c-Si cell concept is a requirement for new types of production equipment, and new equipment on show in Hamburg for c-Si cell production invariably fell into one or more of these categories: handling ultra-thin silicon wafers; providing module interconnections for full back-contact cells; enabling improved current collection and reduced surface losses; and improved metallization schemes for either front or back cell surfaces.
One term that has emerged as a must-have throughout the equipment supply chain is “selective emitter,” representing a new type of c-Si cell, which is immediately associated with higher efficiencies. Selective emitters — talked about in the research community for decades, and now being adopted by the tool suppliers — feature a heavily doped contact area underneath the metallized regions and a lightly doped emitter area between front fingers. They provide an immediate efficiency increase to the standard c-Si cells dominating production output today. A variety of selective emitter schemes are under consideration today: etch-back; screen-printed phosphorous-doped paste; buried contacts; diffusion masking; and laser doping. There are also several variants of laser doping, with the most production-viable being laser-induced melting of predeposited impurities (LIMPID), using either a residual phosphorous layer (typically the PSG layer) or an extra dopant film.
Consequently, the equipment choice for c-Si cell production has never been more varied than on show at this year’s EU PVSEC in Hamburg. While this might make it harder to choose which concept to pursue within high-efficiency cell lines, the focus on efficiency enhancement is a good thing for the c-Si supply-chain as a whole. At the moment, c-Si production equipment selection appears to be mimicking the range of flavors confronting previous equipment suppliers targeting thin-film capex spending: amorphous or tandem; CIGS or CdTe; different panel sizes from Gen. 4 to Gen. 8.5; and the range of TCO and substrate materials being used. Anyone hoping for immediate standardization in solar production equipment may be in for a shock — but it’s better to have a host of technologies competing to improve cell performance than a few standard options failing to deliver the roadmap directives for continuous $/W reduction.
While changing market dynamics catalyzed the shift to new production line equipment, ultimately it will likely be similar market changes that determine the high-efficiency cell concepts and related tooling that come out on top. Once demand cycles swing back to exceed production supply, and high-efficiency production lines are feverishly run at high utilization rates, production volume statistics (average efficiencies, yield levels, production costs, and module prices) can compare the success of many of the new concepts and tooling that were on display at Hamburg.
Finlay Colville received his BSc in physics at the U. of Glasgow in 1990 and PhD in laser physics at the U. of St. Andrews in 1995, and is director of marketing for solar at Coherent Inc., 5100 Patrick Henry Drive, Santa Clara, CA 95054 USA; ph +44-7802-238-775; e-mail Finlay.Colville@coherent.com; http://www.Coherent.com/Solar.