Wafer-based Solar Cells Aren't Done Yet

摘要

The solar industry's recent growth spurt has shown that success brings new challenges. Once content to salvage silicon scrap from the integrated circuit industry, wafer-based solar cells have become the largest consumer of high-purity silicon. As a result, manufacturers of wafer-based silicon solar cells are caught between rising raw material costs on one side, and less expensive alternative technologies on the other. As the name implies, wafer-based silicon cells are fabricated from slices of either single-crystal or multicrystalline silicon. They achieve the highest efficiencies of any commodity photovoltaic technology, second only to cells based on GaAs and other type III-V semiconductors. Single-crystal (c-Si) cells depend on the same Czochralski growth process used to make wafers for integrated circuits, while multicrystalline (mc-Si) cells are cut from cast silicon ingots. Silicon is the largest contributor to the cost of wafer-based cells, accounting for as much as 50% of the total. (Cell cost, in turn, accounts for about half of the total cost of a photovoltaic system.) When the solar energy boom created a severe shortage of high-purity polysilicon, wafer-based cell manufacturers saw their costs rocket upward.