Although photorefractive thin films in the transverse geometry retain most of the basic features of the bulk photorefractive materials, the abrupt changes in the dielectric constant across the boundary regions always accompany polarized charge gratings. These gratings are generated by the perpendicular component of the space charge field and they are absent in the bulk transport equations. Our systematic theoretical calculation indicates that these boundary charge gratings will strongly influence device performance. Adjustment of the dielectric properties of media sandwiching the thin film can serve as a method by which control device performance. ©1997 American Institute of Physics.