OLED Hole Transporting Layer Segmentation for Lifetime Extension
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Solution Overview
Problem
The lifetime of OLED apparatus is shortened due to interface deterioration between emission layers, and there is a need to optimize the structure of hole transporting and injecting layers to improve driving voltage properties.
Innovation Solution
A mixed structure for the hole transporting layer with two materials of different hole mobilities and a hole injecting layer with a balanced ratio of organic to inorganic materials is used to maintain charge balance and reduce interface deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a single material is used in the hole transporting layer, then the device structure is simple, but the lifetime is shortened due to interface deterioration
Solution Approach 1:
The hole transporting layer is divided into multiple sub-layers (first hole transporting layer and second hole transporting layer) with different materials having different hole mobilities. This segmentation prevents excessive hole accumulation at the emission layer interface, reducing interface deterioration and extending device lifetime while maintaining reasonable structural complexity.
Solution Approach 2:
Different regions of the hole transporting layer are assigned different materials with specific hole mobility characteristics. The first hole transporting layer uses a material with higher hole mobility closer to the emission layer to control hole flow, while the second layer uses a material with lower hole mobility. This local differentiation optimizes hole distribution and prevents interface deterioration.
2Reliability
If the hole injecting layer contains only organic material, then the manufacturing is simple, but the charge balance is poor
Solution Approach 1:
The hole injecting layer is formed as a composite layer containing both organic material and inorganic material. The organic material provides good interface contact and charge injection, while the inorganic material enhances charge balance and stability. This composite structure improves charge balance and device reliability while introducing moderate manufacturing complexity.
Data Source
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Figure 3A~3B
AI summary
Discussed is an OLED apparatus which facilitates to improve the lifetime and progressive driving voltage properties, wherein the OLED apparatus includes an anode, a cathode, and a plurality of stacks. Among the plurality of stacks, the first stack closest the anode includes a first emission layer including a blue emission layer, and a hole transporting layer having a first material, and a second material whose hole mobility is smaller than that of the first material.