LCDs are the preferred technology for lightweight and low-power display devices, but their need for a light source and thickness are drawbacks. OLEDs overcome these limitations by using organic light-emitting materials that emit light on their own, making them the next generation of displays. OLED’s thin, bright screens and wide range of application possibilities are expected to drive the future of display technology.
Liquid crystal display (LCD) panels have emerged as the leading display panel due to the need for portable, low-consumption, and lightweight display devices and the increasing demand for flat panel display devices. LCDs are widely used as flat panel displays because they are relatively lightweight and consume less power, but they have the disadvantage of requiring a separate light source on the back of the panel. This increases the overall thickness of the display device and requires a complex design for the placement of the light source and uniformity of illumination. In addition, because the light source is located at the back of the panel, the overall energy efficiency can be reduced, and the brightness and color gamut of the light source are limited.
As the need for technology to overcome these limitations grows, OLEDs (Organic Light(-)Emitting Diodes) are emerging as the next-generation display technology that can replace them. OLED is a device that displays images using organic light-emitting materials that emit light when voltage is applied, and it has a fundamentally different structure from LCD in that it does not require a separate light source device. Each pixel on the screen emits light independently, which reduces unnecessary energy consumption and allows for very thin displays.
The structure of an OLED is basically two electrodes mounted on a transparent substrate made of glass or plastic, with an organic light-emitting material inserted between the two electrodes, consisting of a hole-injection layer, hole-transport layer, light-emitting layer, electron-transport layer, and electron-injection layer. This structure largely determines the luminous efficiency and color reproduction depending on the role played by each layer, and efforts are being made to develop OLEDs with improved performance through various studies.
When a voltage is applied to the anode and cathode of an OLED, holes with a (+) charge are generated on the anode side, and electrons with a (-) charge are generated on the cathode side. When these two are injected into the organic light-emitting material through the hole injection layer and electron injection layer, which are connected to the electrode, respectively, they combine in the light-emitting layer through the transport layer. At this time, the energy contained in the electrons is released, stimulating the organic light-emitting material to generate light. The amount of energy generated and the color of the light generated depends on the type of organic material that makes up the light-emitting layer.
Depending on which organic light-emitting material is used, OLEDs are generally made of multiple layers of thin films. This is because holes and electrons move at different speeds in organic materials, and the purpose is to balance the density of holes and electrons in the light-emitting layer by effectively transporting them through each transport layer to increase recombination efficiency. As the recombination efficiency increases, the luminous efficiency of OLEDs increases significantly, enabling the realization of clearer screens with less power.
These technical advantages allow OLEDs to be thinner and lighter than the currently popular LCDs, as well as much brighter and sharper display devices at the same voltage. These properties have led to OLED’s expanding applications in portable electronics such as smartphones, tablets, and laptops, as well as in a variety of other areas such as large televisions, automotive displays, and even wearable devices. In addition, OLEDs can be used as substrates for glass and plastic, so overcoming the technical limitation of difficulty in scaling up could make it possible to create scroll-like display devices and even use the wall itself as a screen. These possibilities, combined with next-generation smart home technologies, will open the door to a future where users can freely arrange and use displays within their homes.
