Composite Hole-Injection Layer for Organic EL Light Extraction
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Solution Overview
Problem
Organic electroluminescence (EL) devices face challenges in achieving high light extraction efficiency due to light attenuation caused by refractive index differences between layers, and existing materials struggle to balance low refractive index with high heat resistance and reliability.
Innovation Solution
A composite material comprising a first organic compound with a high proportion of carbon atoms forming sp3 hybrid bonds and a second organic compound containing fluorine, which is used for layers such as hole-injection, hole-transport, or charge-generation layers, offering a refractive index between 1.45 and 1.70, high glass transition temperature, and electron-accepting properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a material with low refractive index is used to improve light extraction efficiency, then light extraction efficiency is improved, but heat resistance and reliability deteriorate
Solution Approach 1:
The patent uses a composite material consisting of a host compound and a guest compound where the guest compound molecules are dispersed in the host compound matrix. This composite structure enables the material to simultaneously achieve low refractive index (improving light extraction efficiency) and high glass transition temperature (maintaining heat resistance and reliability), resolving the technical contradiction between these two properties.
Solution Approach 2:
The patent changes the molecular structure parameters of the organic compound by controlling the proportion of sp3 hybridized carbon atoms (20-60%) and introducing fluorine atoms. These parameter changes enable the material to achieve both low refractive index and high thermal stability, simultaneously improving light extraction efficiency and heat resistance.
2Loss of energy
If the refractive index is reduced to improve light extraction, then light extraction efficiency is improved, but device performance and stability worsen
Solution Approach 1:
The composite material system with host and guest compounds allows independent optimization of optical and thermal properties. The host compound provides structural stability and high glass transition temperature, while the guest compound contributes to low refractive index, achieving both improved light extraction efficiency and maintained device performance stability.
Solution Approach 2:
The patent applies local quality by having different molecular regions serve different functions: the host compound matrix provides thermal stability and structural integrity, while the dispersed guest compound molecules provide low refractive index. This local differentiation enables simultaneous achievement of low refractive index and high device stability.
Data Source
AI summary
A composite material with a low refractive index that can be used for a light-emitting device, a light-receiving device, a light-emitting and light-receiving device, and the like is provided. The composite material includes a first organic compound and a second organic compound, the proportion of carbon atoms forming bonds by the sp3 hybrid orbitals in the total number of carbon atoms of the first organic compound is greater than or equal to 23% and less than or equal to 55%, and the second organic compound contains fluorine. Alternatively, an optical device including an anode, a cathode, and a first layer, in which the composite material is included in the first layer, is provided.