Question

Explain the block diagram of OLED. 

Answer 1

Working of an OLED * After the organic material has been applied to the substrate the real working of the OLED begins. * The substrate is used to support the OLED. The anode is used to inject more holes when there is a path of current. The conducting layer is used to carry the holes from the anode. The cathode is used to produce electrons when current flows through its path. The emissive layer is the section where the light is produced. This layer is used to carry the electrons form the cathode. * First, the anode is kept positive w.r.t the cathode. Thus there occurs an electron flow from the cathode to the anode. This electron flow is captured by the emissive layer causing the anode to withdraw electrons from the conductive layer. Thus, there occurs a flow of holes in the conductive layer. As the process continues, the conductive layer becomes positively charged and the emissive layer becomes negatively charged. * A combination of the holes and electrons occur due to electrostatic forces. As the electrons are less mobile than the holes, the combination normally occurs very close to the emissive layer. This process produces light in the emissive region after there has been a drop in the energy levels of the electrons. The emissive layer got its name as the light produced in the emissive region has a frequency in the visible region. The colour of the light produced can be varied according to the type of organic molecule used for its process. To obtain colour displays, a number of organic layers are used. Another factor of the light produced is its intensity. If more current is applied to the OLED, the brighter the light appears. Take a look at the diagram given below.

OLED Diagram * Now consider the process when the anode is negative w.r.t the cathode. This will not make the device work as there will not be any combination of the holes and electrons. The holes will move towards the anode and the electrons to the cathode.