Organic EL Hole Injection Layer with Diffused Electron Material
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Solution Overview
Problem
In organic electroluminescent (EL) devices, achieving balanced hole and electron injection is challenging due to diffusion issues with materials like Li, Cs, which affects light-emitting efficiency and lifespan, leading to suboptimal performance in terms of efficiency and longevity.
Innovation Solution
Incorporating an electron injection layer made of alkali metals or their compounds that diffuse into the hole injection layer, and using a hole transporting layer to prevent direct contact between the electron injection layer and the light-emitting layer, thereby adjusting hole transport and reducing material diffusion into the light-emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating material is doped or laminated on the organic thin film layer between the light-emitting layer and the anode, then carrier balance is improved, but the material diffuses into the organic layer and approaches the light-emitting layer, preventing light emission
Solution Approach 1:
A hole blocking layer is introduced as an intermediary between the insulating material and the light-emitting layer. This layer prevents the insulating material from diffusing into the light-emitting layer while still allowing the insulating material to improve carrier balance in the organic thin film layer, thus resolving the contradiction between improving carrier balance and preventing material diffusion.
Solution Approach 2:
The functional layer between the anode and light-emitting layer is segmented into multiple sub-layers: the organic thin film layer, the hole blocking layer, and the insulating material layer. This segmentation isolates the insulating material from direct contact with the light-emitting layer, preventing diffusion while maintaining the carrier balance improvement function.
2Reliability
If Li, Cs, or similar materials are used in the organic layer between the light-emitting layer and the anode, then carrier balance is improved, but these materials are easily diffused into the organic layer, preventing light emission
Solution Approach 1:
The hole blocking layer serves as a protective intermediary that prevents Li, Cs, or similar materials from diffusing into the light-emitting layer. This allows these materials to be used in the organic thin film layer for improving carrier balance without compromising the light-emitting layer's integrity and extending its operational lifetime.
Solution Approach 2:
The harmful diffusion function of Li, Cs, or similar materials is extracted by introducing the hole blocking layer, which specifically blocks these materials while allowing them to perform their carrier balance function in the organic thin film layer. This separates the beneficial carrier balance effect from the harmful diffusion effect.
3Reliability
If material is added to the organic layer between the light-emitting layer and the anode, then carrier balance is improved, but light emission is prevented
Solution Approach 1:
The hole blocking layer acts as a mediator that allows the insulating material to improve carrier balance in the organic thin film layer while preventing the insulating material from reaching and degrading the light-emitting layer. This maintains both improved carrier balance and light emission functionality.
Solution Approach 2:
The functional layer is segmented into distinct regions with specific functions: the organic thin film layer for carrier balance improvement, the hole blocking layer for preventing material migration, and the light-emitting layer for light emission. This segmentation allows each layer to optimize its function without interfering with others.
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
This configuration improves carrier balance, enhances light-emitting efficiency, and extends the lifespan of the organic functional layer by preventing material diffusion, resulting in a more reliable light-emitting device.
Implementation Method 1
the electron injection material used for the electron injection layer is diffused into the hole injection layer
Data Source
AI summary
In a display panel, a first electron injection layer is formed between an anode and a light-emitting functional layer, and a hole injection layer is formed between the anode and the first electron injection layer. In other words, the hole injection layer, the first electron injection layer, and the light-emitting functional layer are configured to be laminated on the anode in this order. An electron injection material used for the first electron injection layer is diffused into the hole injection layer, and the diffused electron injection material inhibits or promotes hole transportation of the hole injection layer, so that the amount of holes transported to a light-emitting functional layer is adjusted. As a result, the carrier balance is improved.