Collection efficiency of low‐mobility solar cells

An equation for the collection efficiency (i.e., internal quantum efficiency) is derived that can be used for Schottky barrier, metal‐insulator‐ semiconductor, or semiconductor‐electrolyte junction solar cells. It is obtained from an exact solution of the transport equation in the space‐charge region and includes the effects of photogenerated majority carriers. It is shown that these carriers can diffuse to the interface and thereby oppose the minority‐carrier photocurrent by recombination or emission. This effect is shown to be quite significant in reducing the collection efficiency when the majority‐carrier mobility is low and at short wavelengths where the absorption coefficient becomes large.