A light source assembly, a backlight and a display device are provided. The light source assembly comprises a bar-shaped light source unit, which comprises an organic light-emitting diode for emitting light and has a light outgoing side; and a light concentration bar, which has a light incidence surface and a light outgoing surface opposite to each other, the light incidence surface being disposed at an outer side of the light outgoing side of the light source unit and matching with the light outgoing side in size, and the light outgoing surface matching with a light incidence side of a light guide plate in size.