Float-zone silicon for high volume production of solar cells

When solar cells are manufactured by use of float zone (FZ) grown monocrystalline silicon, it is possible to achieve efficiencies near 25%. This value is significantly higher than the typical efficiency of commercial cells (13-16.5%) that is manufactured on Czochralski (CZ) grown monocrystalline or casted polycrystalline silicon. The electronic grade FZ growth process however, requires an expensive form of silicon feedstock material that brings the price of a FZ wafer far above the acceptable range for the PV industry. In order to overcome this dilemma, Topsil has developed a new crystal puller and a new set of process recipes that can accept a larger and rougher type of low cost feedstock. Hereby it is possible to manufacture FZ silicon wafers at the same cost as CZ wafers, without reducing the quality and compromising the efficiency potential of the FZ material.