Red OLED Device with Dual Light-Emitting Layers
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Solution Overview
Problem
Red organic electroluminescent devices face challenges with unbalanced carrier injection leading to low efficiency and brightness, high operating voltage, and rapid efficiency attenuation, along with complex structures that increase production costs and reduce device lifespan.
Innovation Solution
A red organic electroluminescent device with a multilayer structure comprising an anode modification layer, hole transporting-electron blocking layer, hole-dominated light-emitting layer, electron-dominated light-emitting layer, hole blocking-electron transporting layer, and cathode modification layer, where the electron-dominated light-emitting layer includes a rare earth complex as an organic sensitive material to balance carrier distribution and enhance energy transfer, and the hole-dominated light-emitting layer uses specific iridium-based red organic light-emitting materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a multilayer structure with multiple light-emitting layers is used to improve light-emitting effectiveness, then brightness increases, but device complexity and production cost increase
Solution Approach 1:
The device divides the light-emitting function into two distinct layers: a hole-dominated light-emitting layer and an electron-dominated light-emitting layer. This segmentation allows each layer to specialize in transporting one type of carrier, improving overall efficiency while maintaining a manageable structure through functional division rather than adding excessive layers
Solution Approach 2:
Each light-emitting layer serves multiple functions: it acts as both a carrier transport channel and a light emission zone. The hole-dominated layer transports holes and emits light, while the electron-dominated layer transports electrons and emits light, eliminating the need for separate transport and emission layers
2Ease of manufacture
If traditional light-emitting materials are used to simplify device structure, then manufacturing cost decreases, but light-emitting effectiveness and spectral stability deteriorate
Solution Approach 1:
The patent employs composite material systems in each light-emitting layer, combining host materials with specific dopants (iridium complexes in the hole-dominated layer and europium complexes in the electron-dominated layer). These composite structures achieve superior light-emitting effectiveness and spectral stability compared to single materials, while the standardized fabrication process keeps production costs manageable
3Illumination intensity
If carrier injection is increased to improve brightness, then light output increases, but efficiency attenuation accelerates
Solution Approach 1:
The device creates different local environments in each light-emitting layer by optimizing the host-guest ratio and material composition specifically for either hole or electron transport. This local optimization allows high carrier injection rates without causing efficiency roll-off, as each layer is tailored to handle its specific carrier type effectively
Solution Approach 2:
The patent systematically varies key parameters including dopant concentration (0.1-5 wt%), host material selection, and layer thickness to optimize performance. By adjusting these parameters, the device achieves high brightness with delayed efficiency attenuation and extended service life
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves light-emitting effectiveness, spectral stability, reduces operating voltage, delays efficiency attenuation, and extends the service life of the device while simplifying the structure to lower production costs.
Implementation Method 1
the electron-dominated light-emitting layer includes a rare earth complex as an organic sensitive material to balance carrier distribution and enhance energy transfer
Implementation Method 2
When charges are injected into an organic layer between a hole injection electrode and an electron injection electrode, electrons and holes encounter, combined, and then annihilated, and thus light is generated
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention provides a red organic electroluminescent device, composed of a substrate (1), an anode layer (2), an anode modification layer (3), a hole transporting-electron blocking layer (4), a hole-dominated light-emitting layer (5), an electron-dominated light-emitting layer (6), a hole blocking-electron transporting layer (7), a cathode modification layer (8), and a cathode layer (9) arranged in turn, wherein the electron-dominated light-emitting layer (6) is composed of an organic sensitive material, a red organic light-emitting material, and an electron-type organic host material. A rare earth complex having a matched energy level, such as Eu(DBM)3phen or Eu(TTA)3phen is selected as the organic sensitive material, and a trace amount of the same is doped into the electron-dominated light-emitting layer (6), which has the function of an energy transporting ladder and a deep binding center for charge carriers, so as to improve the light-emitting effectiveness, spectral stability, and service life of the device, reduce the operating voltage of the device, and delay the attenuation of the effectiveness of the device.