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2013
Conference Paper
Titel
Laser doping from borosilicate glass for metallization of boron emitters
Abstract
The improvement of the contact resistance with the modification of the dopant profile is investigated for n-type solar cells. Metallization was performed by screen printing. The dopant profile is controlled by laser doping. Different powers of a laser with a wavelength of = 355 nm and a pulse length of Laser ≈ 25 ns were tested. Laser doping was carried out on two emitters (Rsheet ≈ 70 and 90 O/sq.) and their corresponding borosilicate glass (BSG) precursor layers, which were grown with the emitter during tube furnace diffusion. Only a small part of the boron is diffused from the BSG layer into the silicon. This is explained by the low heat diffusion in the BSG layer, since it was found that the surface dopant concentration diffused into silicon increases after laser doping with higher laser powers. The boron profiles obtained by laser doping presents lower surface concentration but deeper dopant profiles than the emitters without laser doping. The emitter saturation current density results indicate that the recombination increases strongly for laser doping samples. Specific contact resistances were reduced half for laser doping samples in comparison to the homogeneous tube furnace diffused emitters, reaching a minimum value of 5.2±1.2 mO·cm2.