Metal Oxide Prism Structure for OLED Light Extraction
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Solution Overview
Problem
Organic electroluminescent elements suffer from low luminous efficiency due to total reflection of light at interfaces with different refractive indices, and existing prism structures are limited by the use of organic materials with low refractive indices, which are difficult to micro-fabricate and lack heat resistance.
Innovation Solution
A high-refractive index prism structure made of metal oxide is formed between the transparent substrate and the electrode on the light output face of the organic electroluminescent element, with the prism vertices facing the substrate, using a method that involves coating an aqueous material containing a metal oxide sol or precursor on an organic prism structure and burning off the organic material at high temperatures to create a stable metal oxide prism structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a prism structure is used to reduce total reflection and improve light output efficiency, then light output efficiency is improved, but the refractive index of the prism structure is limited by organic materials (1.35-1.5) which is lower than the light-emitting layer (1.7 or more)
Solution Approach 1:
The patent changes the material parameter (refractive index) by transitioning from organic materials to inorganic materials for the prism structure. This parameter change enables the prism structure to achieve a refractive index of 1.7 or more, matching and exceeding the light-emitting layer's refractive index, thereby effectively reducing total reflection and improving light output efficiency.
Solution Approach 2:
The patent employs a low-cost fabrication method using a mold to form the prism structure. The mold can be reused multiple times to create prism patterns on substrates, making the manufacturing process economical and scalable. This approach replaces complex precision machining with a simpler, more cost-effective molding technique.
2Ease of manufacture
If organic polymer material is used for the prism structure, then the structure can be easily fabricated, but the heat resistance and stability during storage are insufficient
Solution Approach 1:
The patent uses inorganic materials (such as silicon oxide, titanium oxide, or their composite materials) to fabricate the prism structure. These materials provide both the desired optical properties (high refractive index) and improved thermal stability and storage reliability, while still allowing for relatively easy fabrication through molding techniques.
3Loss of energy
If the refractive index of the prism structure is increased to match the light-emitting layer, then total reflection is reduced, but the manufacturing precision and micro-fabrication capability are challenged
Solution Approach 1:
The patent employs a low-cost fabrication method using a mold to form the prism structure. The mold can be reused multiple times to create prism patterns on substrates, making the manufacturing process economical and scalable. This approach replaces complex precision machining with a simpler, more cost-effective molding technique.
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
This configuration significantly reduces total reflection and enhances light output efficiency, resulting in a high-brightness organic electroluminescent element with improved heat resistance and manufacturing stability.
Implementation Method 1
burning off the organic material at high temperatures to create a stable metal oxide prism structure
Implementation Method 2
a prism structure effective in converging light have been proposed
Implementation Method 3
light entering into each interface at an angle of not less than its critical angle is reflected totally by the interface back to the original layer
Data Source
AI summary
Provided is an organic electroluminescent element, comprising a transparent substrate and at least one organic layer containing a light-emitting layer between a pair of electrodes, wherein the transparent substrate is formed on the light output face side of the organic layer, a prism structure containing metal oxide is formed between the transparent substrate and an electrode formed on the light output face of the organic layer, and the prism vertexes therein are present facing the transparent substrate.Also provided are a method of manufacturing a prism structure containing metal oxide on a transparent substrate, and a method of manufacturing an organic electroluminescent element by using the substrate having a prism structure.