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Mallinckrodt Baker FinalDR 5/1/10 12:40 Page 16
the multicrystalline texturing etch process:
uniformity is more homogeneous across the wafer
surface, defect etching is significantly reduced,
and the reaction is more controlled – operating at
room temperature with virtually no foaming. It is
anticipated that these chemistries will soon
become broadly available to improve surface
texturing processes across the industry.
Better chemistries enhance yield
It is also anticipated that engineered chemistries
can improve c-Si solar cell fabrication yield through contamination, in both remnants of silicon carbide
more efficient manufacturing processes, in some particles and organic chemicals. Typically, wafer
cases leveraging only incremental increases in providers use a multi-step wet chemical process to
cost to generate significant reductions in cost/Wp. remove these contaminants, relying on large
quantities of bulk hydrofluoric acid.
Issue VI 2009
For example, improving texturing processes to Mallinckrodt Baker is working with several leading
increase etch uniformity also reduces defect wafer suppliers on engineered chemistries that will
etching. Reductions in defect etching help consolidate these processes into fewer steps;
eliminate weak points in the wafer structure, which there is also potential for integrating the texturing
can break or shatter during cell manufacturing or process into the wafer cleaning steps, so that
module assembly. This can reduce waste product, wafer suppliers can offer pre-textured products to
ensure greater process yields, and help prevent cell manufacturers. line shutdowns or other manufacturing inefficiencies.
This approach may help consolidate chemistry
Supply chain considerations costs and generate savings – demonstrating how
The global c-Si industry is still testing a variety of suppliers such as Mallinckrodt Baker, who are
enterprise models to determine what is the most engaged in supplying and optimizing multiple c-Si
cost-effective and productive approach to process steps, can provide unique insight and
organizing the solar cell manufacturing supply perspective into application solutions and process
chain. Currently, the industry is fragmented, with advances. Some may claim that using engineered
some companies specializing in ingot production, chemistries, with incrementally higher costs
wafer fabrication, solar cell production and/or compared to commodity chemicals, will negatively
module assembly. Some of the largest companies impact yield and increase costs. However, careful
are investing in full-scale vertical integration, consideration suggests that the right application of
controlling the process from silicon feedstock to specialty chemicals can have a dramatic positive
finished module. Wet chemistry suppliers believe impact on total COO.
that there are opportunities to achieve improved
economies of scale through supply chain The cost of wet chemicals used in c-Si
consolidation. For example, the wafer wire-sawing manufacturing is relatively small: approximately
process, where individual wafers are cut from the 3 to 4% of total material costs. Yet, it has been
silicon ingot, generates significant surface demonstrated that one additional step in post-
emitter fabrication cleaning can generate a 0.3%
improvement in cell efficiency. And advances
continue: Mallinckrodt Baker’s two newest post
emitter surface modification products, PV-162 and
PV-200, offer cell efficiency improvements up to
0.7% absolute. They also show increased
efficiency for both inline and POCl processes on
multicrystalline and monocrystalline wafers.
Therefore, replacing bulk commodity chemicals
with engineered chemistries, a relatively modest
increase in materials costs, has the potential to
yield a significant improvement in cell efficiency,
ultimately driving down cost per watt and
driving up the value of the line’s output.
Increasingly, leading edge crystalline solar cell
manufacturers are appreciating the strategic
Graph 1: Revenue for 50MW Solar Line at Various Cell Efficiencies: advantage of this value equation. See Graph 1:
Achieving cell efficiency gains through the use of performance chemistries Revenue for 50MW Solar Line at Various Cell
can have a dramatic impact on revenue. Efficiencies
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