A light-emitting device is provided. The light-emitting device includes a first electrode; a second electrode; a subminiature light-emitting device disposed between the first electrode and the second electrode; and a planarization layer disposed between the first electrode and the second electrode. The planarization layer is prepared by curing a composition including an oligomeric compound that includes a group represented by Formula A, a group represented by Formula B, a group represented by Formula C, or any combination thereof: Substituents in Formula A, Formula B, and Formula C may be understood as described in connection with the detailed description.