OLED Cap Layer Refractive Index Stacking for Heat-Resistant Light Extraction
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Solution Overview
Problem
Existing light-emitting devices face challenges in achieving high emission efficiency, reliability, and low power consumption, particularly in environments requiring high-temperature driving or preservation.
Innovation Solution
Incorporating a cap layer with a stacked structure of organic compounds, including at least one substance with a carbazole skeleton, where the difference in ordinary refractive indices between the substances is greater than 0.1, enhancing light extraction efficiency and improving heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cap layer is added to improve light extraction efficiency, then emission efficiency is improved, but device complexity increases
Solution Approach 1:
The cap layer is constructed as a composite structure containing a first organic compound layer and a second organic compound layer with different refractive indices. This composite material approach enables simultaneous optimization of light extraction efficiency and structural functionality, resolving the contradiction between improved emission efficiency and increased device complexity by making the complex structure functionally beneficial.
Solution Approach 2:
The invention utilizes parameter changes in refractive index by selecting organic compounds with specific refractive index ranges (first compound: 1.40-1.70, second compound: 1.70-2.00). This parameter optimization enables effective light extraction without requiring excessive structural complexity, as the refractive index difference alone provides the necessary optical functionality.
2Productivity
If organic compounds with high refractive index are used to extract light, then light extraction efficiency is improved, but heat resistance deteriorates
Solution Approach 1:
The cap layer combines a first organic compound (lower refractive index, better heat resistance) with a second organic compound (higher refractive index, better light extraction). This composite material strategy allows the system to achieve high light extraction efficiency while maintaining adequate heat resistance through the synergistic properties of the combined materials.
Solution Approach 2:
Different regions of the cap layer have different optical properties: the first organic compound layer provides thermal stability and structural integrity, while the second organic compound layer provides enhanced light extraction. This local differentiation of material properties allows each substance to optimize for its specific function without compromising the other.
3Device complexity
If a single-layer cap structure is used, then device complexity is reduced, but light extraction efficiency is insufficient
Solution Approach 1:
The invention transitions from a single-layer cap structure to a two-layer composite cap structure where the first organic compound layer is deposited followed by the second organic compound layer. This composite structure achieves superior light extraction efficiency by creating multiple interfaces with different refractive indices, thereby reducing the overall impact of any single interface and maximizing light extraction through cumulative effects.
Solution Approach 2:
The cap layer is segmented into two distinct functional layers: the first organic compound layer that provides structural foundation and thermal stability, and the second organic compound layer that provides enhanced optical functionality. This segmentation allows each layer to be optimized independently for its specific function while working synergistically as a whole.
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 a light-emitting device with improved emission efficiency, reliability, and reduced power consumption, suitable for high-temperature environments, and stable mass production.
Implementation Method 1
With respect to light with the same wavelength that is any value in the range from 380 nm to 760 nm, a difference between the ordinary refractive index of an evaporated film of the first substance and the ordinary refractive index of an evaporated film of the second substance is greater than or equal to 0.1
Data Source
AI summary
A light-emitting device including a first electrode, a second electrode, a light-emitting layer positioned between the first electrode and the second electrode, and a cap layer in contact with the second electrode is provided. The second electrode is positioned between the light-emitting layer and the cap layer. The cap layer includes at least a first substance and a second substance. With respect to light with the same wavelength that is any value in the range from 380 nm to 760 nm, the difference between the ordinary refractive index of an evaporated film of the first substance and the ordinary refractive index of an evaporated film of the second substance is greater than or equal to 0.1. Any one of the first substance and the second substance is an organic compound having a carbazole skeleton.