The core structure of OLED display is like a precise optical "sandwich", mainly composed of the following key components working together to achieve its self luminous characteristics and excellent image quality:
Substrate:
Function: The physical foundation and supporting platform of the entire display panel.
Material: Usually glass (rigid OLED) or flexible polymer (such as polyimide PI, used for flexible/foldable OLED). The flatness, transparency (crucial for bottom emitting OLEDs), and thermal stability of the substrate are key factors.
Thin film transistor array:
Function: Located on the substrate, it forms a "neural network" for pixel addressing. Each pixel (or sub-pixel) is controlled by one or more TFTs, which precisely determine the magnitude of the current flowing through the organic material of the OLED below, thereby controlling the brightness of the pixel.
Material: Usually made of amorphous silicon, low-temperature polycrystalline silicon, or metal oxide semiconductor materials.
Anode:
Function: Inject holes into the organic functional layer when applying voltage.
Material: Usually transparent conductive material, the most commonly used is indium tin oxide. For top emitting OLEDs, the anode may also have reflectivity.
Organic functional layer:
This is the core area of OLED emission, which is composed of multiple layers of extremely thin organic material films stacked together, usually made by vacuum evaporation or solution processing technology:
Hole injection layer: reduces the energy barrier of anode injected holes and improves efficiency.
Hole transport layer: Efficiently transport holes from the anode to the luminescent layer.
Luminous layer: Core layer! The injected electrons and holes recombine here, releasing energy and emitting light in the form of photons. Use different luminescent materials (small molecules or high molecular weight polymers) according to the desired color. A pixel typically contains three independent sub-pixel light-emitting layers (RGB arrangement) of red, green, and blue, or uses a white light+filter scheme.
Electronic transport layer: Efficiently transport electrons from the cathode to the luminescent layer.
Electron injection layer: reduces the energy barrier of injected electrons at the cathode and improves efficiency.
Cathode:
Function: Inject electrons into the organic functional layer when applying voltage.
Material: Usually a low work function metal or alloy, such as magnesium silver alloy, calcium, aluminum, etc. In bottom emitting OLEDs, the cathode needs to be as thin as possible to ensure light transmission; In top emitting OLEDs, the cathode is typically semi transparent or reflective.
Encapsulation layer:
Function: An absolutely critical protective barrier! OLED organic materials are extremely sensitive to water vapor and oxygen, and even slight intrusion can lead to pixel failure (black spots) or overall performance degradation. The encapsulation layer tightly isolates the external environment.
Form:
Traditional rigid OLED: using another glass cover plate, sealing the edges with glass powder or resin, and filling the inside with desiccant.
Flexible/Thin Film Packaging: Multiple layers of alternating inorganic and organic thin films are directly deposited on the OLED structure to form an ultra-thin and flexible protective layer. This is the key technology for implementing flexible screens.
Polarizing film:
Function: OLED screens produce strong specular reflection in ambient light, which seriously affects visibility. Polarizing film is attached to the outermost layer of the screen, mainly to significantly reduce the reflection of ambient light, improve the contrast and readability of the screen in bright environments. At the same time, it also determines the polarization direction output of light.
Touch sensor layer:
Function: Implement touch function (for touch screens).
Location: Usually on the packaging layer or polarizer, or integrated inside the display panel (such as On Cell or In Cell technology). It can be a capacitive touch film (ITO or metal mesh) or other sensing technology.
Cover glass/protective layer:
Function: The outermost physical protection to prevent scratches and impacts.
Material: Usually reinforced glass (such as Corning Gorilla Glass) or transparent polymer film (used for flexible screens).
Driver Integrated Circuit:
Function: Although it does not directly constitute the physical structure of the screen, it is the "brain" and "power source" of the display screen. contain:
Gate driver chip: controls the row scanning of TFT array.
Source driver chip: provides accurate data voltage signals for the columns of TFT arrays.
Timing controller: receives image data and control signals from the device's main processor, and coordinates the timing of the gate and source drivers.
Power management IC: Provides precise voltage and current required for OLED pixels and driver circuits.
In summary, OLED display is an organic whole highly integrated with precision electronic control (TFT, driver IC), efficient charge injection and transfer (electrodes), core luminescence (organic functional layer), tight protection (packaging), and optical optimization (polarizer) components. Its self luminous characteristics eliminate the need for backlight modules in traditional LCDs, making it the structural foundation for achieving ultra-thin, flexible, high contrast, and fast response.