Effects of bimolecular recombination on photocurrent and photoinduced discharge

Abstract

The effects of bimolecular (Langevin) recombination of charge carriers on the photocurrent in the constant‐voltage mode and on the surface potential decay in the open‐circuit (or xerographic) mode are studied. By solving the charge‐carrier transport equations numerically, it is possible to treat cases of practical interest, e.g., transport with recombination of more than 1 CV’s worth of charge carriers, field‐dependent mobilities, and nonuniform generation of charge‐carrier pairs. The calculation of photocurrent in the constant‐voltage mode justifies Hughes’s use of the small‐signal formula in the interpretation of the large‐signal data. In the open‐circuit mode, the difference between the small‐signal formula and the calculation taking into account the space‐charge effects becomes more significant. The natures of the contrast potential and the reciprocity relation are examined.