Rapid Thermal Processing for Front and Rear Contact Passivation

Rapid firing processes are well known to allow improvements in solar cell contacts, particularly for the rear contact. Previous results characterizing the quality of a rear aluminum-alloyed back surface field have measured the effective surface recombination velocity, which depends not only on the material parameters of the back surface field, but also on the base doping. This paper shows that the determination of the recombination current density in the back surface field via photoconductance measurements is an accurate technique to measure the back surface field, independent of the base resistivity. Results show that fast firing conditions give the lowest recombination, but that the firing conditions can be altered substantially while still allowing high open circuit voltages.