An organic light emitting phenomenon denotes a phenomenon where electrical energy is converted into light energy by using an organic material. That is, in a case where an organic material layer is disposed between an anode and a cathode, when a voltage is applied between the anode and the cathode, the anode injects a hole into the organic material layer, and the cathode injects an electron into the organic material layer. The hole and the electron which are injected into the organic material layer are combined to generate an exciton, and when the exciton is shifted to a ground state, light is emitted.
Since an interval between the anode and the cathode is short, an organic light emitting device is easy to have a short circuit defect. Due to a step in a structure of the organic light emitting device and roughness of coating, the anode can directly contact the cathode, or the short circuit defect can occur because a thickness of an organic layer is progressively thinned in an area where occurrence of the short circuit defect is predicted. The defective region provides a low-resistance path which enables a current to flow, and for this reason, a current can hardly flow or cannot at all flow through the organic light emitting device. Consequently, an output of light emitted from the organic light emitting device is reduced, or light is not emitted from the organic light emitting device. In a multi-pixel display device, the short circuit defect causes a dead pixel which cannot emit light or emits light having intensity less than average light intensity, causing the degradation in display quality. For lighting or a low resolution, due to the short circuit defect, a large portion in a corresponding region cannot operate. In order to prevent the short circuit defect, organic light emitting devices are conventionally manufactured in a clear chamber. However, the short circuit defect is not effectively removed even in a very clear environment. In a method where the number of short circuit defects is reduced by increasing an interval between the anode and the cathode, a thickness of the organic layer further increases than a thickness which is actually necessary to operate a device. Such a method causes an increase in the manufacturing cost of organic light emitting devices, and cannot fully remove the short circuit defect.
USPTO Backgrounds
USPTO Backgrounds