Minority-carrier accumulation at the base edge of a junction space-charge region under short-circuit conditions

Abstract

A new boundary condition is derived for the base edge of a p n junction space-charge region of a solar cell subjected to short-circuit conditions. This condition is expressed as an effective surface recombination velocity for minority carriers which equals the ratio of the diffusion coefficient to the extrinsic Debye length. The same condition applies at the collector edge of a quasi-neutral base of a transistor in the forward active mode. The accumulation of minority carriers due to the finite value of the recombination velocity can affect transient responses especially in solar cells that are lightly doped or at low temperatures. Further, this accumulation and the associated space-charge-region recombination current can decrease the short-circuit current in some cells.