A backlight module for illuminating a display is described. The backlight module may be provided in an electronic device along with a light source for illuminating an LCD display. The backlight module includes a diffuser, a light guide having a top surface and a bottom surface, a reflector, and a prism structure positioned between the light guide bottom surface and the reflector. The prism structure has a plurality of prisms extending towards the light guide. The prism structure may include a film or a top portion of the reflector having a plurality of prisms extending towards the light guide.