OLED Substrate Electron Diffusion Layer Hole Transport Control
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Solution Overview
Problem
OLED display substrates suffer from low luminous efficiency due to the faster transport speed of holes in the light-emitting layer compared to electrons, leading to exciton formation at the interface rather than in the light-emitting layer.
Innovation Solution
Incorporating an electron diffusion layer with a first luminescent material, where the transport speed of holes generated by the anode layer is less than in the light-emitting layer, allowing holes and electrons to meet and generate excitons within the electron diffusion layer, thereby improving luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the light-emitting layer uses conventional materials with high hole transport speed, then the device can maintain simple structure, but the luminous efficiency decreases due to exciton formation at the interface rather than in the light-emitting layer
Solution Approach 1:
The patent divides the light-emitting region into two distinct functional layers: a first light-emitting layer with high hole transport speed and a second light-emitting layer with low hole transport speed. This segmentation allows each layer to perform its specific function optimally - the first layer generates excitons efficiently while the second layer ensures their utilization, thereby resolving the contradiction between structural simplicity and luminous efficiency.
Solution Approach 2:
The patent applies local quality by assigning different material compositions and transport characteristics to different regions of the light-emitting layer. The first light-emitting layer uses materials optimized for hole transport (e.g., Alq3, BCP), while the second light-emitting layer uses materials optimized for exciton formation and emission (e.g., Ir(ppy)3, BCP). This local differentiation ensures that each region performs its specific function optimally, improving overall luminous efficiency without requiring complete structural redesign.
2Speed
If the hole transport speed in the light-emitting layer is increased, then the device can achieve faster response, but the excitons form at the interface instead of within the light-emitting layer, reducing luminous efficiency
Solution Approach 1:
The patent segments the light-emitting layer into two distinct sub-layers with different hole transport speeds. The first light-emitting layer has high hole transport speed to ensure rapid charge carrier movement, while the second light-emitting layer has low hole transport speed to ensure excitons form within the layer rather than at the interface. This segmentation allows both speed and efficiency requirements to be met simultaneously in different regions.
Solution Approach 2:
The second light-emitting layer acts as an intermediary between the first light-emitting layer and the hole block layer. It receives excitons from the first layer and ensures they recombine with holes within this layer rather than at the interface, thereby mediating the interaction between charge carriers and preventing energy loss at the interface while maintaining fast response characteristics.
3Loss of energy
If the doping proportion of sensitizing material is increased, then the luminous efficiency improves, but the material composition becomes more complex and harder to manufacture
Solution Approach 1:
The patent applies local quality by optimizing the doping proportion of sensitizing material specifically in the second light-emitting layer, while keeping the first light-emitting layer with lower or no sensitizing material doping. This localized optimization improves luminous efficiency in the critical region where excitons form, without unnecessarily complicating the entire device structure or manufacturing process.
Solution Approach 2:
The patent optimizes the doping proportion parameter of the sensitizing material in the second light-emitting layer to achieve the optimal balance between luminous efficiency and manufacturability. By carefully controlling this parameter (e.g., using specific concentrations of Ir(ppy)3 or other sensitizing materials), the patent maximizes efficiency while maintaining reasonable manufacturing complexity levels.
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 addition of the electron diffusion layer enhances luminous efficiency by ensuring excitons are formed within the layer, exciting the luminescent material and emitting light, thus improving the display substrate's performance.
Implementation Method 1
a material of the electron diffusion layer includes a first luminescent material... holes and electrons to meet and generate excitons within the electron diffusion layer, thereby improving luminous efficiency
Implementation Method 2
exciting the luminescent material and emitting light
Data Source
AI summary
Provided is a display substrate including a base substrate, an anode layer, a light-emitting layer, an electron diffusion layer, a hole block layer and a cathode layer which are sequentially stacked along a direction away from the base substrate, wherein a material of the electron diffusion layer comprises a first luminescent material, and a transport speed of holes generated by the anode layer in the electron diffusion layer is less than a transport speed of the holes in the light-emitting layer.