TiO2 Scattering Layer for OLED Light Extraction
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Solution Overview
Problem
Current OLED devices suffer from low light extraction efficiency due to total internal reflection and waveguide effects caused by differences in refractive indices between the organic light-emitting layer and the glass substrate, resulting in only about 20% of generated light being emitted, while 80% is lost.
Innovation Solution
A light extraction substrate with a scattering layer formed from TiO2, incorporating irregular-shaped voids and a planarization layer from organic/inorganic hybrimer, which creates a multi-refractive-index core-shell structure to scatter light and improve extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar glass substrate is used, then manufacturing is simple and cost is low, but light extraction efficiency is poor due to total internal reflection and waveguide effects
Solution Approach 1:
The patent applies porous materials by forming a scattering layer with controlled porosity on the glass substrate. The porous structure creates air-substrate interfaces that scatter light and reduce total internal reflection, improving light extraction efficiency while maintaining the simplicity of using a glass substrate base
Solution Approach 2:
The patent creates a composite structure by combining the glass substrate with a scattering layer formed from sol-gel processed materials. This composite approach integrates the optical scattering function into the substrate structure, enhancing light extraction while maintaining manufacturing feasibility
2Loss of energy
If the scattering layer porosity is increased to improve light scattering, then light extraction efficiency improves, but non-radiative energy transfer increases reducing OLED reliability
Solution Approach 1:
The patent applies local quality by creating specific porosity distributions and controlling the local optical properties of the scattering layer. The sol-gel process allows precise control over pore size, shape, and distribution, optimizing light scattering while minimizing areas that could cause non-radiative energy transfer
Solution Approach 2:
The patent utilizes parameter changes by controlling the sol-gel processing parameters (precursor composition, drying conditions, firing temperature) to achieve optimal porosity levels. This enables tuning of the scattering layer properties to balance light extraction enhancement with prevention of non-radiative energy transfer
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 significantly enhances light extraction efficiency, contributing to the reliability and performance of OLED devices by increasing the amount of emitted light and reducing manufacturing costs through optimized refractive index management.
Implementation Method 1
a scattering layer formed from TiO2, incorporating irregular-shaped voids and a planarization layer from organic/inorganic hybrimer, which creates a multi-refractive-index core-shell structure to scatter light
Implementation Method 2
the efficiency with which light generated by the light-emitting layer is extracted... depends on the refractive indices of OLED layers... total internal reflection originating from the difference in refractive indices between the glass substrate and ambient air
Data Source
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AI summary
The present invention provides a light extraction substrate for an organic light emitting device, comprising: a base substrate; a scattering layer formed on the base substrate and made of TiO2; a plurality of first light scatterers formed inside the scattering layer and having a porous form; and a flat layer formed on the scattering layer, wherein the scattering layer is internally permeated by a part of the materials constituting the flat layer.