Traditional information medium, such as newspaper and magazine, is no long appreciated since mankind has been in the information age, and display technology is born. Organic light-emitting diode (OLED) has merits such as self-luminous, fast response, broad perspective, thin volume and flexibility. Organic light-emitting diode (OLED) has already applied in mobile phone, tablet, television and wearable devices nowadays.
Lighting Principle of Organic Light-Emitting Diode (OLED)
The anode is usually transparent to ensure the emergent of light. As a kind of transparent metal oxide semiconductor, indium tin oxide (ITO) is frequently used for anode. Due to incompatibility between anode and carrier transport layer, the hole injection layer should be introduced to modify the interface between anode and hole transport layer, and then help more holes enter hole transport layer. Similarly, electron transport layer acts as the same role. The cathode is typically adopting metal thin film. The emitting layer is the core functional layer of the whole organic light-emitting diode (OLED). The light emitting mechanism of organic light-emitting diode contains five steps:
- Injection of carriers: Electrons from cathode and holes from anode will enter the organic functional layer between electrodes under the external electric field.
- Transport of carriers: Injected electrons and holes will transport to electron transport layer and hole transport layer respectively.
- Recombination of carriers: Electrons and holes will be bound up together by the Coulomb force, and formed excitons in the electric
- Transport of excitons: Excitons start to transport under the electric field, and energy will be transmitted to light-emitting molecules. Electrons will be drivingto excitation state from the ground
- Light-emitting process: Radiation decay and generated photons, then releasesluminous energy.
Manufacturing Process of Organic Light-Emitting Diode (OLED)
Magnet in Organic Light-Emitting Diode (OLED) Deposition Apparatus
The evaporation process of light-emitting diode (OLED) needs to finish in the high vacuum cavities of deposition apparatus, and organic materials will be evaporated by the crucible. The glass substrates place on the special holder, then metal shadow masks will be placed under the substrates to dominate the patterns.
In order to ensure the substrates have ideal patterns, there is a magnet array should be placed on top of the substrate to attract the metal shadow masks, hence substrates can fit with masks closely. In fact, the magnetic field strength acting on different positions of the metal shadow mask is not same due to many factors. The coloring film of the pixel will be squeezed by the metal shadow mask because of higher magnetic force and thus lead to film discontinuous, eventually caused bad weather-ability. On the other hand, metal shadow mask cannot be fit closely with substrate, resulting in film disperse and reduction of valid film area.
The magnet array in deposition apparatus is similar like magnetic chuck, and the technical specification for this holder magnet includes dimension, appearance and consistency of magnetic performance. Magnets with dimension oversize will affect evenness of substrates, and consistency of magnetic performance will be evaluated by the deviation of central point gauss values. In order to enhance the testing efficiency and reliability, SDM team has introduced special automotive magnetization and testing equipment to meet the customer’s requirements in organic light-emitting diode (OLED) industry.
