AMOLEDs are self-luminous displays based on organic materials, which became commercially viable thanks to mechanical engineers’ improvements in drive methods and the development of precise production processes. Mechanical engineering technologies such as active drive, TFT devices, and sealing processes played a major role in this process.
‘Amoled’ is the nickname of a mobile phone and its display device that was launched in July 2009 by a South Korean mobile phone manufacturer. The full name is AMOLED, which stands for Active Matrix Organic Light Emitting Diode, which literally means ‘active organic light-emitting diode’. The name refers to the principle, material, and driving method that produces light.
OLED (organic light-emitting diode) is a self-luminous display device that uses the principle that when an electric current is applied to an organic compound, the electrons in the material absorb energy, rise to a high state and fall back to a low state, and emit the difference in energy as light. The term ‘self-luminous’ is an important feature that distinguishes it from LCDs (liquid crystal display), which are conventional flat panel display devices, and refers to the property of a material to emit light on its own. LCDs cannot light up on their own, so a separate light source must be placed behind the panel. This structural difference not only limits LCDs’ ability to minimise panel thickness, but also means that light passes through the panel to the eye, causing image quality to vary depending on the viewing angle. OLEDs were developed as an alternative to address these shortcomings, allowing for sharper and more consistent picture quality.
OLEDs were developed and patented by Dr C.W. Tang of Kodak in 1982, and since then, many labs have been working to improve the intensity, efficiency, and duration of light emission. This research has been active in the development of organic materials used for light emission and in structural research to improve light emission efficiency, resulting in the development of phosphorescent organic materials in 1998 that can achieve three to four times higher efficiency than conventional fluorescent materials. In addition, in order to overcome the limitations of light emitted by a single organic material, a structure was developed in which layers were stacked on top of and below the organic material, which acted as an injection and transport of electrons and holes, in order to overcome the limitations of light emitted by a single organic material. This is one of the core technologies of OLEDs and has contributed to a significant improvement in luminous efficiency.
However, many technical challenges still remained before OLED technology could be commercialised, with mechanical engineers playing a key role in how OLED devices are driven and the processing processes to incorporate them into products. First, it was important to develop an effective way to drive OLEDs. Initially, the passive matrix method, which uses electrodes that are orthogonal to each other to generate light from an external signal and output light to the screen, was the dominant method used. However, despite its simple structure, the passive method had the disadvantages of high voltage losses due to current flowing through even non-light-emitting pixels and the inability to light up multiple pixels at the same time. To overcome these limitations, an active matrix driving method was introduced. This method applies current to each pixel individually, allowing for high resolution and minimal power loss. For this reason, small display devices such as mobile phones mainly adopt active drive, which is called AMOLED.
In order for AMOLEDs to become commercially viable, they require not only mechanical design, but also sophisticated processing processes. OLEDs have a stacked structure, with each layer having a very small thickness. The precise stacking of these thin layers onto a substrate requires a high degree of precision. The process can involve depositing a gaseous material onto the substrate, or spreading a liquid material uniformly and converting it to a solid state. Determining and applying the most appropriate method for this process is crucial to producing high-quality AMOLEDs.
In addition, organic materials, the main material of OLEDs, are very sensitive to moisture and oxygen in the air and can be easily damaged. Therefore, an encapsulation process that completely protects the device from these external environments is crucial at the commercialisation stage. Managing the heat and other physical stresses generated during this process is also essential, and mechanical engineers have developed a variety of protective designs that meet these conditions and applied them to actual production processes to make AMOLEDs commercially viable.
The commercialisation of AMOLEDs has required not only research and development, but also a mechanical process design that enables automation and mass production. AMOLED is a very precise display device, and it is impossible for humans to manually fabricate it during production. Therefore, all processes are performed by machines, and it is necessary to connect these machines organically and automatically to maximise the efficiency of production. To this end, research and development by mechanical engineers has been essential for the design and manufacture of the machines used in each process, as well as the optimisation of the production process.
For example, the development of TFT (thin-film transistor) devices has been a key contributor to maximising the performance of AMOLEDs. TFTs are the devices that deliver electrical signals to each pixel, allowing the pixels to emit light, and they play a key role in increasing resolution and reducing power consumption in small displays. These technical factors have made it possible for AMOLED to be commercialised in a wide range of applications, including smartphones, TVs, and wearable devices.
Finally, AMOLEDs must undergo numerous tests and quality checks before they are ready for production. Various tests are required to ensure the durability, reliability, and screen quality of the product, while mechanical engineers are constantly improving and optimising the process to ensure that the products produced perform at their best.
In the end, the commercialisation of AMOLEDs is the result of a combination of research and development, as well as collaboration across many different fields. Mechanical engineers have played a key role in the design and manufacturing process that has enabled OLED technology to become commercially viable, resulting in the high-performance display devices we use today.
