A light output device comprises a first and a second substrate arrangement (1,2), the first substrate arrangement (1) comprising a light output surface of the device. An electrode arrangement (3a,3b) is sandwiched between the substrate arrangements and at least one light source (4) is connected to the electrode arrangement. The first substrate (1) arrangement comprises a light diffuser for changing the level of uniformity of the light output from the light source and the second substrate (2) arrangement comprises a light scattering or reflecting layer. This arrangement uses a scattering substrate arrangement for the substrate from which illumination is provided. In order to enhance the level of uniformity, the opposite substrate arrangement is also either scattering or reflecting.