Surface Passivation of Crystalline Silicon Solar Cells by Atmospheric Pressure Chemical Vapor Deposition

SiO
₂
films prepared by atmospheric pressure chemical vapor deposition (APCVD) were investigated for surface passivation of crystalline Si solar cells. The passivation effects of APCVD SiO
₂
for p-type Si substrates were evaluated by measuring excess minority carrier lifetimes. Effective surface recombination velocities S
_eff
were decreased by successive annealing in N
₂
atmosphere at 300-700 degC without the degradation of the bulk lifetime. A substantial reduction of S
_eff
was observed especially after annealing over 500 degC. To investigate the origin of this improvement, interface state density D
_it
and fixed charge density Q were extracted from capacitance-voltage curves of metal-oxide-semiconductor structures. The results revealed that the decrease of the S
_eff
was caused from the decrease of D
_it
and the increase of Q/D
_it
ratio induced by the annealing. The field-effect passivation attributed to a large Q/D
_it
was discussed using the extended Shockley-Read-Hall model