As described above, the electrode power supply line VSS is arranged in the peripheral area PA of the substrate 100. In this regard, the electrode power supply line VSS may include the same material as the first source electrode 215a and the first drain electrode 215b in the display area DA, and may be arranged on the same layer as the first source electrode 215a and the first drain electrode 215b. That is, during a manufacturing process, the electrode power supply line VSS may be formed from the same material layer as the first source electrode 215a and the first drain electrode 215b at the same time. Accordingly, the electrode power supply line VSS may have the same layered structure as the first source electrode 215a and the first drain electrode 215b.

A first insulating layer 140 that is a planarization layer may be arranged over the first thin-film transistor 210. For example, as illustrated in FIG. 3, when an organic light-emitting diode is arranged over the first thin-film transistor 210, the first insulating layer 140 may generally planarize a top surface of a protective layer covering the first thin-film transistor 210. The first insulating layer 140 may include an organic material such as, for example, acryl, benzocyclobutene (BCB), hexamethyldisiloxane (HMDSO), or the like. FIG. 3 illustrates that the first insulating layer 140 has a single-layer structure, however, the present disclosure is not limited thereto. For example, in an exemplary embodiment, the first insulating layer 140 may be variously modified, and thus may have a multi-stack structure.