An organic light emitting device according to one or more embodiments includes a gate line, a data line intersecting the gate line, a switching thin film transistor connected to the gate line and the data line, a driving thin film transistor connected to the switching thin film transistor, and a light emitting diode (LED) connected to the driving thin film transistor. The switching thin film transistor includes a control electrode connected to the gate line, a crystalline semiconductor overlapping the control electrode, and an input electrode and an output electrode are spaced apart from each other on the crystalline semiconductor, wherein the control electrode and the gate line are respectively disposed under and on the crystalline semiconductor and include different materials.