OLED Light Extracting Layer Using Hollow Polyimide Balls
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Solution Overview
Problem
Conventional organic light emitting diode (OLED) devices suffer from poor light extracting efficiency due to a reduced scattering effect caused by the high index of refraction of scattering media, such as TiO2 and ZrO2, which limits photon emission to only 20% to 30%.
Innovation Solution
An OLED device with a light extracting enhanced layer comprising hollow polyimide balls and a polyimide matrix, formed by chemical imidization, is introduced. This layer has a thickness between 2 μm and 6 μm and a ratio of hollow polyimide balls to polyimide matrix of 40% to 60%, creating a high contrast in refractive indices to enhance scattering and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If nanometer/micrometer metal oxide particles with high index of refraction (TiO2, ZrO2) are added as scattering medium, then light propagation direction is changed to emit more photons, but the index of refraction difference between substrate and scattering particles is reduced, scattering effect is greatly reduced, and light extracting efficiency is reduced
Solution Approach 1:
The patent changes the refractive index parameter of the scattering medium from high-index metal oxides (TiO2, ZrO2 with n>2.0) to low-index hollow polyimide balls (n<1.5), creating a large refractive index difference with the substrate (n=1.5) that enhances scattering effect and light extracting efficiency
Solution Approach 2:
The patent uses composite material structure consisting of hollow polyimide balls dispersed in a matrix material, where the hollow structure provides low effective refractive index while the polyimide matrix provides structural support and adhesion to the substrate
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 use of hollow polyimide balls and polyimide matrix in the light extracting enhanced layer significantly improves the scattering effect and light extracting efficiency, increasing the emission of photons beyond conventional limits.
Implementation Method 1
a light extracting enhanced layer located below the glass substrate, wherein a material of the light extracting enhanced layer comprises a first material with a first index of refraction and a second material with a second index of refraction, a difference value between the first index of refraction and the second index of refraction is greater than a preset threshold value
Data Source
AI summary
An organic light emitting diode includes a glass substrate, a first electrode, an organic light emitting layer, a second electrode, and a light extracting enhanced layer below the glass substrate or on the second electrode. Material of the light extracting enhanced layer has a first material with a first index of refraction and a second material with a second index of refraction.