Multi versus mono: Which wafer wins?

Higher efficiencies mean mono wafers look set to recapture some share from the dominant multis in the crystalline silicon solar cell market.


This is a favourite and often-asked question in the solar industry.

Back in 2007 the split between monocrystalline and multicrystalline wafer production was about 50:50. This ratio has now fallen to about 30:70 as multi has been able to push cost advantages in a market that has been driven by large-scale utility projects and keenly focused on upfront module costs.

Figure 1:  Monocrystalline versus multicrystalline silicon wafer production share

Graph for Multi versus mono: Which wafer wins?

Source: NPD Solarbuzz Polysilicon and Wafer Supply Chain Quarterly Report

Even so, the debate about which technology offers the greater value and which will gain share in the future is ongoing.

Monocrystalline wafers enable an absolute cell efficiency advantage of around 2 per cent. However, standard monocrystalline wafers typically sell for about a 30 per cent premium over multicrystalline wafers. This price gap tends to vary according to market conditions as well as manufacturing technology trends.

Multicrystalline wafers have both substantially increased efficiency and lowered costs over the past several years. Improved crystallisation techniques have produced a new class of high efficiency (HE) multi wafers that support standard cells now approaching 18 per cent efficiency and greater than 250W sixty-piece modules.

At the same time, larger ingots and other process improvements have helped cut wafering costs in half. These advances have been major contributing factors to multi wafer share gains.While average multicrystalline silicon ingot sizes are likely to continue to grow, HE multi efficiency gains may start to slow as crystallisation improvements are widely realised.

At the same time, monocrystalline wafer makers are also improving performance and reducing costs. Rising adoption of diamond wire sawing and the potential for wide-scale commercialisation of continuously-fed Czochralski (CCz) mono ingot growth may help reduce the cost gap with multi wafers in the future.

Moreover, as PV module cost have been thoroughly wrung out in recent years, greater attention is being focused on reducing balance-of-systems (BOS) costs. Higher efficiencies from modules built with mono wafers can significantly reduce BOS costs by requiring less system real estate, less racking and wiring, and reducing installation and maintenance costs. These savings in turn lower total installed system costs.

Both multi and mono wafers are expected to play important and varying roles in the future of the solar industry, but the trend toward higher monocrystalline solar cell efficiencies is expected to start gradually swinging the market share pendulum back towards mono wafers.

Originally published by NPD Solarbuzz. Reproduced with permission. 

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