Organic EL Device Refractive Index and Thermal Stability
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Solution Overview
Problem
Organic electroluminescence (EL) devices face challenges in achieving high light extraction efficiency, low driving voltage, high heat resistance, long lifetime, and low power consumption due to limitations in refractive index and material reliability.
Innovation Solution
A light-emitting device structure incorporating a first organic compound with a high proportion of carbon atoms forming sp3 hybrid bonds and a second organic compound containing fluorine, with specific refractive index and glass transition temperature ranges, along with a third organic compound for improved hole injection and electron-blocking properties, is employed to enhance emission efficiency and reduce driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low refractive index material is used to improve light extraction efficiency, then light extraction efficiency is improved, but material reliability and heat resistance deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive index of the organic compound within the range of 1.45 to 1.70 and the glass transition temperature within 80°C to 150°C. This optimization balances the refractive index (affecting light extraction efficiency) with thermal stability (affecting material reliability), resolving the contradiction between these two parameters through quantitative material selection
Solution Approach 2:
The patent employs composite materials by combining multiple organic compounds with specific properties: a hole injection layer material, a hole transport layer material, and a light-emitting layer material. Each layer uses compounds selected for their specific refractive indices and thermal properties, creating a composite structure that achieves both high light extraction efficiency and material reliability through synergistic material selection
2Loss of energy
If a low refractive index material is used to improve light extraction efficiency, then light extraction efficiency is improved, but heat resistance deteriorates
Solution Approach 1:
The patent resolves the contradiction between light extraction efficiency and heat resistance by independently optimizing two critical parameters: refractive index (1.45-1.70) for optical performance and glass transition temperature (80°C-150°C) for thermal stability. This dual-parameter optimization allows the material to maintain both low refractive index for efficient light extraction and high heat resistance for stable operation
Solution Approach 2:
The patent uses composite material structures where each layer is composed of specific organic compounds selected for their thermal and optical properties. The hole injection layer, hole transport layer, and light-emitting layer are each formulated with compounds that provide the necessary heat resistance while maintaining appropriate refractive indices, creating an overall system that balances thermal stability with optical efficiency
3Device complexity
If organic EL device structure is simplified to reduce device complexity, then device complexity is reduced, but emission efficiency deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the organic EL device into distinct functional layers: hole injection layer, hole transport layer, and light-emitting layer. Each layer is assigned specific organic compounds with optimized properties for its particular function, allowing the device to achieve high emission efficiency through specialized material placement while maintaining a relatively simple overall structure without requiring complex additional components
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 proposed structure achieves high emission efficiency, low driving voltage, and improved heat resistance, leading to a longer device lifetime and reduced power consumption.
Implementation Method 1
By application of voltage to the organic EL device, light emitted from the light-emitting organic compound can be obtained
Implementation Method 2
Light attenuation due to reflection caused by a difference in refractive index between adjacent layers is a factor of a decrease in light extraction efficiency
Data Source
AI summary
A light-emitting device with high emission efficiency is provided. A light-emitting device with a low driving voltage is provided. The light-emitting device includes a first electrode, a first layer over the first electrode, a second layer over the first layer, a light-emitting layer over the second layer, and a second electrode over the light-emitting layer. The first layer includes a first organic compound, and the second layer includes a second organic compound. The proportion of carbon atoms forming bonds by the sp3 hybrid orbitals to the total number of carbon atoms in the first organic compound is higher than or equal to 23 percent and lower than or equal to 55 percent. The second organic compound contains fluorine.