Organic EL Capping Layer Materials for Light Extraction and Lifespan
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Solution Overview
Problem
Conventional organic electroluminescent (EL) elements face challenges in achieving high luminance, efficient light emission, and long lifespan, particularly due to issues with light extraction efficiency and material durability.
Innovation Solution
The use of a capping layer composed of an arylamine compound with a specific chemical structure, combined with a luminous layer containing a heterocyclic compound with a fused ring structure, enhances the light extraction efficiency and stability of the organic EL element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a metal mask is used for forming a capping layer under high temperature conditions, then alignment accuracy is maintained, but the metal mask is distorted by heat causing decreased alignment accuracy
Solution Approach 1:
The patent replaces the durable metal mask with a disposable photoresist pattern that is applied at low temperature, used for deposition, and then removed. This disposable approach avoids the heat distortion problem of metal masks while maintaining alignment accuracy through photolithography patterning.
Solution Approach 2:
The patent replaces the mechanical metal mask system with a photochemical patterning system using photoresist and UV exposure. This substitution allows precise pattern formation at low temperatures without the thermal distortion issues inherent in metal masks.
2Use of energy by moving object
If ZnSe is deposited using a metal mask, then a capping layer with high refractive index is formed, but deposition by sputtering affects the light emitting element and ZnSe cannot be deposited at an accurate position
Solution Approach 1:
The patent replaces thermal sputtering deposition with a low-temperature deposition method applied to a photoresist-patterned substrate. This allows precise ZnSe deposition only in the desired capping layer regions without the broad deposition effects and positioning errors associated with sputtering through metal masks.
Solution Approach 2:
The patent performs preliminary photolithography patterning to create a photoresist mask before deposition. This preliminary action defines the exact deposition positions, ensuring that ZnSe is deposited only where the capping layer is needed, with high positional accuracy.
3Use of energy by moving object
If Alq3 is used as a capping layer, then the refractive index is adjusted, but Alq3 has weak absorption near 450 nm causing decreased color purity and light extraction efficiency in blue light emitting elements
Solution Approach 1:
The patent changes the material parameter of the capping layer from Alq3 to ZnSe, which has different optical properties. ZnSe has strong absorption in the blue region (450 nm) while maintaining the desired refractive index, thus improving both light extraction efficiency and color purity for blue light emitting elements.
4Use of energy by moving object
If a capping layer with high refractive index is added, then light extraction efficiency is improved, but the element structure becomes more complex and manufacturing becomes more difficult
Solution Approach 1:
The patent merges the capping layer formation with the existing photolithography and deposition processes. By using photoresist patterning (already part of the manufacturing process) to define the capping layer position, and depositing ZnSe in the same process flow, the structural complexity is minimized while achieving high light extraction efficiency.
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 results in an organic EL element with improved luminance, light emission efficiency, power efficiency, and extended lifespan, while also effectively absorbing harmful wavelengths of sunlight.
Implementation Method 1
a capping layer with a high refractive index... has a high absorbance at a wavelength of 400 nm to 410 nm in an absorption spectrum
Implementation Method 2
the light is totally reflected at an interface between the luminous layer and the other film... a capping layer with a high refractive index... improve light extraction efficiency
Data Source
AI summary
The present invention provides various organic electroluminescent elements using a material for a capping layer and a material for a luminous layer, in which the material for a capping layer uses an arylamine material that exhibit excellent stability and durability in the form of a thin film, especially a specific amine compound having a high refractive index and having a high absorbance within a wavelength range from 400 nm to 410 nm in the absorption spectrum at a concentration of 10−5 mol/L; and in which the material for a luminous layer uses a compound containing a heterocyclic compound that has a specific fused ring structure.