Organic Electroluminescent Device Host-Dopant Energy Levels
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Solution Overview
Problem
Existing organic electroluminescent devices have limitations in emission efficiency and lifetime, with unclear quantitative relationships between organic compounds in light-emitting layers and a lack of clear host-guest type configurations.
Innovation Solution
An organic electroluminescent device with a light-emitting layer comprising a host material and dopants, where the first dopant facilitates intersystem crossing and the second dopant is a phosphorescent material for efficient energy transfer, with specific excitation level correlations to enhance energy transfer and emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light-emitting layer with multiple organic compounds is used, then emission efficiency can be improved, but the quantitative relationship and host-guest configuration are unclear, leading to device reliability issues
Solution Approach 1:
The patent applies parameter changes by precisely controlling the triplet lowest excitation levels of different dopants relative to the host material. The first dopant has a triplet lowest excitation level higher than the host, while the second dopant has a triplet lowest excitation level lower than the host, creating a specific energy level parameter configuration that enables efficient energy transfer while maintaining device reliability.
Solution Approach 2:
The patent uses composite materials by combining the host material with two different dopants (first and second dopants) in the light-emitting layer. This composite structure allows for optimized energy transfer pathways where the first dopant facilitates intersystem crossing and the second dopant enables phosphorescent emission, achieving both high emission efficiency and reliable device performance.
2Device complexity
If conventional organic compounds are used in the light-emitting layer, then device structure can be simplified, but lifetime and power consumption performance are insufficient
Solution Approach 1:
The patent changes the energy level parameters of the organic compounds used in the light-emitting layer. By selecting compounds with specific triplet lowest excitation levels that satisfy the relationshipTd1 > TH > Td2, the patent achieves improved device lifetime and power consumption performance while maintaining a relatively simple three-component light-emitting layer structure.
3Loss of energy
If energy transfer is optimized between organic compounds, then emission efficiency improves, but the energy transfer mechanism becomes more complex
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different dopants based on their local energy level characteristics. The first dopant (with higher triplet energy than host) specifically facilitates intersystem crossing, while the second dopant (with lower triplet energy than host) specifically enables phosphorescent emission. This localized functional assignment simplifies the overall energy transfer mechanism while achieving high emission efficiency.
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 solution results in improved efficiency and longer lifetime of the organic electroluminescent device by optimizing energy transfer and emission processes, allowing for more efficient light emission and reduced power consumption.
Implementation Method 1
an energy transfer takes place from the lowest excitation singlet state of the third organic compound to the lowest excitation singlet state of the first organic compound, and transits to the lowest triplet state by intersystem crossing
Implementation Method 2
a second organic compound and a third organic compound, wherein the second organic compound is a phosphorescent material which emits light
Implementation Method 3
an energy transfer takes place from the lowest excitation triplet state of the first organic compound to the second lowest excitation triplet state of the second organic compound
Data Source
AI summary
The present invention provides a phosphorescent luminescent device which has high-efficiency and a long lifetime. The organic electroluminescent device according to the present invention includes a pair of electrodes and an organic layer disposed between the pair of electrodes, wherein the organic layer has at least a light-emitting layer, and the light-emitting layer include at least a host material and dopants containing at least a first dopant and a second dopant, and wherein a triplet lowest excitation level of the first dopant is higher than a triplet lowest excitation level of the host material, and a triplet lowest excitation level of the second dopant is lower than a triplet lowest excitation level of the host material.