Polysilicon used for semiconductor applications typically requires very high purity of 11N (99.999999999 per cent) and very low levels of contaminants. Semiconductor polysilicon is a high value-added segment, but future demand growth in this mature market is only expected to be modest.

Solar PV-grade polysilicon has less stringent purity requirements, but it has the potential for very high growth, when solar panel demand is strong. However, the growth trajectory in polysilicon supply and end-market demand is not always directly correlated.

NPD Solarbuzz believes it may take three to six months after polysilicon is produced for it to be converted into wafers and cells, and then shipped as finished modules through distribution channels for installation. This lag time can push polysilicon demand higher than module demand, in a rapidly expanding market.

“Conversely, the amount of silicon required per watt at the module level has been declining steadily each year,” said Charles Annis, vice president at NPD Solarbuzz. “Solar supply chain companies have lowered the number of grams-per-watt by reducing wafer thickness and kerf loss, increasing yields in all manufacturing steps, reducing module loss, and continuously raising panel efficiency.”

Between 2005 the end of 2014, the average amount of silicon used in a solar module fell by 55 per cent, to approximately 5 grams-per-watt. This trend is expected to continue, though at a slower rate, as many of the material reduction steps implemented to decrease polysilicon consumption have now been exhausted.

Robust end-market solar-PV demand continues to drive polysilicon production levels. This, in turn, raises module efficiencies and reduces costs, which will remain important priorities across the entire solar-PV supply chain, according to Annis.