In this work we propose the modeling of rear passivation effect on the performance of the polycrystalline solar cell. The rear passivation layers can reflect photons to the interior of the cell. Thus, prolonging their target and making easy their absorption while decreasing the surface recombination velocities of minority carriers at the base area. The conversion efficiency is estimated at 10.49 % for an optimal rear passivation using thin oxide /Silicon Nitride/Silicon oxide. In addition, Front passivation by the silicon nitride of polycrystalline solar cell has been proposed. We noted a very clear improvement of the efficiency for high Ammonia (NH₃) to Silane (SiH₄) gas flow ratio, the efficiency reaches 12.88% for R=10. We have also contributed in the modelling of grain boundaries current density in polysilicon. Electrical simulation shows the influence of grain boundaries surface recombination velocity in the optimization of the conversion efficiency. We noted that the sufficient and optimal surface recombination velocity 10⁴ cm/s at the emitter heavily doped gives the optimum output. Therefore, the reduce of the grain boundaries surface recombination velocity at base region slightly doped increases the performance of the cell, it's about 10 cm/s. The current density at the grain boundaries is closely related to the potential barrier at grain boundaries. Indeed, the increase in current density indicates a decrease in potential barrier. Finally, we can conclude that Silicon nitride/ P⁺ N / thin oxide /Silicon Nitride/Silicon oxide multilayer structure can be preferment for photovoltaic applications.