Organic EL Device Hole Transporting Zone Light Extraction
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Solution Overview
Problem
Existing organic electroluminescence devices face challenges in achieving high luminous efficiency and longevity due to inefficiencies in the recombination of holes and electrons, particularly in the ratio of singlet to triplet excitons and the structure of the hole transporting zone.
Innovation Solution
The organic electroluminescence device incorporates a specific structure with a hole transporting zone comprising a first anode side organic layer and a second anode side organic layer, where the first layer contains a first organic material and the second layer contains a monoamine or diamine compound, both materials being different, with a refractive index relationship that enhances light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-layer hole transporting zone is used, then the device structure is simple, but the luminous efficiency is insufficient due to poor light extraction
Solution Approach 1:
The hole transporting zone is divided into multiple layers: a first hole transporting layer adjacent to the anode, a second hole transporting layer adjacent to the emitting region, and an intermediate layer between them. This segmentation allows optimization of light extraction at different interfaces while maintaining functional separation of hole transport tasks.
Solution Approach 2:
An intermediate layer is introduced between the first and second hole transporting layers. This intermediate layer serves as a mediator to optimize optical coupling and light extraction between the two functional layers, improving overall light extraction efficiency without compromising hole transport functionality.
2Ease of manufacture
If the hole transporting zone uses uniform materials, then the manufacturing process is simple, but the recombination efficiency of holes and electrons is insufficient
Solution Approach 1:
Different materials are used in different regions of the hole transporting zone. The first hole transporting layer uses materials optimized for hole injection from the anode, while the second hole transporting layer uses materials optimized for hole transport to the emitting region. This local optimization of material properties enhances overall recombination efficiency.
Solution Approach 2:
The hole transporting zone employs composite material structures with distinct layers having different material compositions. Each layer is designed with specific material characteristics suited to its functional requirements, creating a composite structure that optimizes both hole injection and transport processes.
3Device complexity
If a single-layer hole transporting zone is used, then the device complexity is low, but the device lifetime is reduced
Solution Approach 1:
The hole transporting zone is segmented into multiple layers, each potentially made from materials optimized for different aspects of hole transport and stability. This segmentation allows selection of materials with superior stability characteristics for critical interfaces, thereby extending device lifetime despite increased structural complexity.
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 luminous efficiency and extends the device's lifetime by optimizing the recombination process and light extraction, leading to enhanced performance in organic electroluminescence devices.
Implementation Method 1
a refractive index NM1 of constituent materials contained in the first anode side organic layer and a refractive index NM2 of a constituent material contained in the second anode side organic layer satisfy a relationship of a numerical formula below
Implementation Method 2
When voltage is applied to an organic EL device, holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected holes and electrons are recombined in the emitting layer to form excitons.
Data Source
AI summary
An organic EL device includes an emitting region between a cathode and an anode, a first anode side organic layer, and a second anode side organic layer, in which the emitting region includes at least a first emitting layer, the first emitting layer contains a first host material, a first additional host material, and a first luminescent compound, the first anode side organic layer contains first and second organic materials, a content of the first organic material is less than 50 mass %, the second anode side organic layer contains a second hole transporting zone material, the first emitting layer is an emitting layer that emits fluorescence, and a refractive index NM1 of constituent materials in the first anode side organic layer and a refractive index NM2 of a constituent material in the second anode side organic layer satisfy a relationship of Numerical Formula NM,NM1>NM2.(Numerical Formula NM)