Numerical simulation of edge effects in silicon hetero-junction solar cells

Photovoltaic characteristics in silicon hetero-junction solar cells are affected by the peripheral structure of the cell, and this is commonly referred to as the edge effect. We systematically investigated the edge effect on the photovoltaic characteristics of silicon hetero-junction solar cells by simulation. The effect strongly depends not only on the dimension of the periphery but also on the lifetime of the photo-generated carrier in crystalline Silicon (c-Si), the surface recombination velocity at the c-Si/a-Si:H interface, and the surface recombination velocity at the end of the c-Si wafer. Therefore, how these parameters affect the photovoltaic characteristics was simulated for three cases: (1) when a sufficiently large peripheral region passivated by a-Si:H is shielded from light, (2) when the length of the periphery is finite and the surface recombination of the photo-generated carriers at the peripheral end occurs, and (3) when the periphery is partially or entirely illuminated. Moreover, on the basis of the simulation technique developed, we proposed a new electrode configuration that is suitable for small area test cells with several cm2.