Low Refractive Index Compounds for OLED Light Extraction

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Solution Overview

Problem

Current double-layer capping layer materials in OLED devices, composed of low and high refractive index compounds, fail to enhance luminous efficacy and reduce color shift effectively.

Innovation Solution

Development of low refractive index compounds with specific structural features, such as the presence of fluorine and cyano substituents, paired with high refractive index compounds to form a double-layer capping layer, improving light extraction efficiency and reducing color shift in OLED devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If current double-layer CPL material (low-refractive index compound and high-refractive index compound) is used, then light extraction efficiency is improved, but color shift problem is not effectively reduced

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidcolor shift control

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent modifies the refractive index parameter of the low-refractive index compound by introducing specific molecular structures with fluorine atoms and cyano groups. These structural modifications change the optical parameters (refractive index values) to achieve better optical interference effects that simultaneously improve light extraction efficiency and reduce color shift across different viewing angles.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite capping layer system by combining specifically designed low-refractive index compounds (with fluorine and cyano substitutions) and high-refractive index compounds. This composite material approach allows optimization of both light extraction efficiency and color stability through the synergistic interaction of the two layers with different optical properties.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If double-layer CPL is designed to enhance efficiency, then luminous efficacy is improved, but device complexity increases

Engineering Contradiction:

Improveluminous efficacyVSAvoidcapping layer structure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent divides the capping layer into two distinct functional segments: a low-refractive index layer (with fluorine/cyano compounds) and a high-refractive index layer. This segmentation allows each layer to perform its specific optical function independently, optimizing light extraction through controlled interference while maintaining a manageable structural complexity through clear functional differentiation.

Inventive Principle:

Principle #1Segmentation

3Use of energy by moving object

If OLED device operates at high efficiency, then luminous output is improved, but angle dependence increases

Engineering Contradiction:

Improveluminous outputVSAvoidviewing angle independence

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The patent optimizes the refractive index parameters of the capping layer materials to control optical interference conditions. By carefully selecting and adjusting the refractive indices of the low and high refractive index compounds, the optical path difference is controlled to minimize wavelength shifts across different emission angles, thereby reducing color shift and improving viewing angle independence while maintaining high luminous output.

Inventive Principle:

Principle #35Parameter changes

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 compounds enhance light extraction efficiency, alleviate angle dependence, and effectively block water and oxygen, thereby improving the performance and longevity of OLED display panels while minimizing color shift.

Implementation Method 1

the compounds with low refractive index provided by the present disclosure contain fluorine, cyano or an alkyl substituent with large steric hindrance. When paired with a compound with high refractive index, it can be used as a double-layer CPL material in an OLED device, which can improve the light extraction efficiency

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

effectively block water and oxygen in the external environment, protect the OLED display panel from water and oxygen erosion

Methodology Applied

Scientific EffectPermeation barrier: Permeation

Data Source

PatentUS20240336637A1Low refractive index compounds and uses thereof

Publication Date: 2024.10.10 WUHAN TIANMA MICRO ELECTRONICS CO LTD

AI summary

Provided is a compound with low refractive index, having a structure represented by Formula I. The compounds with low refractive index provided by the present disclosure contain fluorine, cyano or alkyl substituents with large steric hindrance. When paired with a compound with high refractive index as a double-layer CPL material in an OLED, the light extraction efficiency and luminous efficacy of the top-emitting organic optoelectronic device are improved, the angle dependence of the light emission of OLED is alleviated, while water and oxygen in the external environment are effectively blocked to protect the OLED display panel from water and oxygen erosion, and the color shift problem is effectively reduced.