Enhancement of silicon solar cell performance by introducing selected defects in the SiO2 passivation layer

Deep level defects usually have harmful effect on solar cells. In this work it is shown; however, that correct incorporation of selected defects in the silicon oxide region of a silicon solar cell improves its efficiency. This is demonstrated by numerical simulation of n-type silicon-based solar cell including deep level defects in the silicon dioxide (SiO2) passivation layer. The defect density was varied to study its effect on the solar cell performance. The selected defects assist the majority carrier's transport through their energy levels that are echoing with the band edge state, and repulse the minority carrier, therefore reducing recombination. It was found that well-defined deep defect density and a minimum thickness of the SiO2 passivation layer are required for high efficiency Si-based solar cells. The defects must be of a high density (similar to 10(17 )cm(-3)), and energetically situated above the conduction band minimum (CBM) of the adjacent Si layer. With these considerations, the conversion efficiency attained 26 %. Furthermore, in the case of very thin passivation layer, the current through defects did not have any effect on the solar cell performance since the tunneling current goes directly through this tin layer.