1. Field
An exemplary embodiment relates to a display device, and more particularly, to an organic light emitting device.
2. Description of the Related Art
The importance of flat panel displays has recently increased with the growth of multimedia. Various types of flat panel displays such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and organic light emitting devices have been put to practical use.
In particular, an organic light emitting device may have a high response speed (of 1 ms or less), a low power consumption, and a self-emitting structure. The organic light emitting device may also not have viewing problems. As such, the organic light emitting device has been considered as a next generation display device.
The organic light emitting device and an active matrix type organic light emitting device depending on a driving manner. In the passive matrix type organic light emitting device, an anode electrode and a cathode electrode cross each other at a right angle, and signal lines are selected to thereby drive the organic light emitting device. In the active matrix type organic light emitting device, a thin film transistor is connected to each pixel electrode, and the organic light emitting device is driven depending on a voltage maintained by capacitance of a capacitor connected to a gate electrode of the thin film transistor.
The organic light emitting device may include a light emitting diode including a first electrode, a light emitting layer, and a second electrode. More specifically, the light emitting diode includes the first electrode supplying holes to each subpixel, the second electrode supplying electrons to each subpixel, and the light emitting layer interposed between the first electrode and the second electrode. The light emitting layer forms excitons by combining the holes received from the first electrode and the electrons received from the second electrode to thereby emit light.
The light emitting diode is formed by evaporating a metal having a high work function such as indium-tin-oxide (ITO) and indium-zinc-oxide (IZO) and then patterning the evaporated metal to form the first electrode in each subpixel, and forming a third insulating film that covers a portion of the first electrode and defines each subpixel.
The light emitting layer is formed on an exposed area of the first electrode exposed by the third insulating film. The light emitting layer may include an organic material or an inorganic material. In case that the light emitting layer may include an organic material, the light emitting layer formed of the organic material may be formed using a thermal evaporation method in which the light emitting layer is evaporated upward by applying heat to an evaporation source.
In the thermal evaporation method, in case that the substrate is close to the evaporation source, an evaporation thickness is uniform. On the contrary, in case that the substrate is far away from the evaporation source, a scattering angle of the evaporation source in an outermost area of the substrate is small. Therefore, an evaporation shadow phenomenon, in which a predetermined area of the light emitting layer is not evaporated, occurs. Accordingly, the evaporation shadow phenomenon reduces the reliability of the organic light emitting device and generates dark spots on an image.