OLED P-type Charge Generation Layer Dopant-Free Hole Transport
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Solution Overview
Problem
Organic light emitting display devices face challenges with increased driving voltage and reduced efficiency due to the use of P-type charge generation layers with dopants, which also increase manufacturing costs.
Innovation Solution
The use of a hole transport layer with a combination of materials having a higher absolute value of HOMO energy level than the P-type charge generation layer, and potentially forming the hole transport layer in two layers to adjust energy levels and mobility, reducing the driving voltage and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a P-type charge generation layer with dopant is used, then charge balance between emission parts is adjusted, but driving voltage increases and efficiency decreases
Solution Approach 1:
The patent removes the dopant from the P-type charge generation layer, extracting the harmful element that caused increased driving voltage and reduced efficiency. The charge generation layer is formed using only host material without dopant addition, thereby eliminating the voltage increase while maintaining charge balance functionality through the host material's inherent properties.
Solution Approach 2:
The patent changes the compositional parameter of the charge generation layer by eliminating the dopant component entirely. This parameter change from a doped structure to a dopant-free structure fundamentally alters the electrical characteristics, reducing driving voltage while maintaining the layer's charge generation capability through the host material's properties.
2Reliability
If a P-type charge generation layer with dopant is used, then charge balance between emission parts is adjusted, but manufacturing cost increases
Solution Approach 1:
The patent extracts and removes the expensive dopant material from the charge generation layer formulation. By forming the layer using only the host material without additional dopant components, the manufacturing cost is reduced while the charge balance function is maintained through the host material's inherent electrical properties.
Solution Approach 2:
The patent replaces the expensive dopant material with a simpler, more cost-effective approach using only the host material. This substitution eliminates the need for costly dopant chemicals and their associated handling, storage, and processing requirements, thereby reducing overall manufacturing costs.
3Device complexity
If hole transport layer is formed with single material, then structure is simple, but hole-injecting characteristic changes and efficiency reduces
Solution Approach 1:
The patent employs a composite hole transport layer structure consisting of multiple materials with different functions. The first hole transport material provides hole injection and transport, while the second hole transport material with higher hole mobility enhances the overall hole transport capability. This composite structure improves efficiency by optimizing both hole injection and transport characteristics through material combination.
Solution Approach 2:
The patent applies the local quality principle by assigning different functional characteristics to different materials within the hole transport layer. The first material is optimized for hole injection from the charge generation layer, while the second material is selected with higher hole mobility to optimize hole transport to the emission layer. Each material's properties are tailored to its specific functional requirement within the layer.
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 reduces the driving voltage and maintains or improves efficiency, while also reducing manufacturing costs by eliminating the need for expensive dopant materials in the P-type charge generation layer.
Implementation Method 1
a hole injected from the anode moves to the emission layer through the hole transport layer
Implementation Method 2
an electron injected from the cathode moves to the emission layer through the electron transport layer
Implementation Method 3
The electron and the hole which are carriers are recombined in the emission layer to generate an exciton, and light is emitted when the generated exciton is shifted from an excited state to a ground state
Data Source
AI summary
Discussed is an organic light emitting display device. The organic light emitting display device can include a first emission part, a second emission part on the first emission part, and a first P-type charge generation layer between the first emission part and the second emission part. The first emission part includes a first hole transport layer, a first emission layer, and a first electron transport layer. The second emission part includes a second hole transport layer, a second emission layer, and a second electron transport layer. The second hole transport layer and the first P-type charge generation layer are disposed adjacent to each other. The second hole transport layer includes a first material and a second material. The first material has an absolute value of a HOMO energy level which can be greater than an absolute value of a LUMO energy level of the first P-type charge generation layer.