An organic light emitting device (OLED) is presented that includes: signal lines formed on a substrate; thin film transistors formed on the substrate and electrically connected to the signal lines; a first passivation layer having a concavo-convex surface; a first electrode formed on the first passivation layer; a partition formed on the first electrode and having an opening extending to the first electrode; a light emitting member formed in the opening and covered by a second electrode. The refractive indices of the light emitting member and the first passivation layer are different, and the refractive indices of the first passivation layer and the first electrode are different. The concavo-convex surface increases the luminescent surface area without decreasing the opening size, thereby enhancing the luminous power per unit pixel electrode. Forming an interface of materials whose refractive indices differ by at least 0.2 within the OLED increases light extraction efficiency.