Model for Localized States Distribution and Light Dependent Effects in Amorphous Silicon Solar Cells

Abstract

The localized state density for amorphous Si (a·Si) can be reasonably approximated by a U-shaped hyperbolic function for the theoretical analysis of the potential profile in the depletion layer of a·Si Schottky barrier solar cells. The photocurrent dependence on the width of the depletion layer has been theoretically analyzed with emphasis on the effect of minority carrier recombination in the depletion layer and the shrinkage of the depletion width under sunlight due to hole trapping. The detailed analysis shows that the minority carrier diffusion length L _p is about 0.15 µm and the optimum width of the undoped layer in Schottky barrier solar cells is in the range of 0.2–0.44 µm for the minimum density of gap states of 10¹⁷–10¹⁶ cm^-3eV^-1, respectively.