On the majority carrier collection in p +-p-n + and n +-p-p + silicon solar cells

Abstract

The spectral responses of a few bifacial n +-p-p + silicon solar cells, 220 – 330 μm thick, were measured to investigate the possibility of majority carrier collection in n +-p-p + back-surface field and p +-p-n + front-surface field silicon solar cells. It was found that, under low level conditions, any appreciable collection of photogenerated majority carriers has to be field aided. Therefore, under low level conditions hole collection may contribute substantially to the photocurrent density of a p +-p-n + or n +-p-p + cell and this may come from the p + or p region provided that not only is the concentration of photogenerated holes in that region substantially large but also there exists a built-in electric field due to the impurity gradient to aid the process. For high level conditions, however, holes can be collected from the uniformly doped p base region with or without the aid of an electric field.