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

SiO₂ films prepared by atmospheric pressure chemical vapor deposition (APCVD) were investigated for surface passivation of crystalline Si solar cells. The passivation effects of APCVD SiO₂ 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 N₂ 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