FEATURE MANUFACTURING


SEEING LIGHT


THE


Lasers can help to make solar cells more efficient and cheaper to manufacture, as Rob Coppinger discovers


16 PHOTOVOLTAICS 2012


Using light to manufacture devices that capture light could be viewed as ironic, but it is still true that lasers are now encroaching on processes to make photovoltaics more efficient and cheaper to produce.


Selective laser doping is one approach for making solar cells more efficient. The basic idea is that the crystalline solar cell has contact points, referred to as fingers, on top of the cell that act as electrical contacts to collect the sunlight’s photon’s electrons. To increase the effectiveness of these contact points and therefore the cell’s overall efficiency the contacts are doped using a laser. The laser needs to be selective, because doping between the so-called fingers will mean a greater likelihood of the photon’s electrons recombining. Recombination means fewer electrons collected and these losses lead to a drop in efficiency.


‘The laser is the perfect tool for this, because you can selectively melt the silicon and phosphor, which is already on top of the cell is then diffusing into the silicon, because the silicon has been melted,’ says Christof Siebert, senior manager industry


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