A light-emitting device includes a plurality of light-emitting elements or light sources and a flexible pad for positioning and conforming the light-emitting device to a portion of a body of a user. The flexible pad includes a three-dimensional structure having a plurality of protrusions for contacting a skin of the portion of the body when the light-emitting device is applied to the portion of the body by the flexible pad. Further, the three-dimensional structure includes a plurality of recesses for creating a clearance between the skin and the flexible pad when the light-emitting device is applied to the portion of the body, and a plurality of apertures for engaging with the plurality of light-emitting elements. Each protrusion includes an extended part and a withdrawn part, where the extended part is further extended than the withdrawn part, and the extended part is configured to contact the skin.