OLED Optical Path Control Layer for Light Extraction
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Solution Overview
Problem
Organic light emitting devices (OLEDs) suffer from low optical extraction efficiency, with most photons being trapped due to internal reflection, limiting their optical output to about 20%, and existing solutions often complicate manufacturing processes.
Innovation Solution
Incorporating an optical path control layer with high transmittance and refractive index matching the transparent electrode, made of materials like Al2O3 or IZO, between the substrate and transparent electrode to optimize light emission, reducing refractive index difference and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a scattering center structure is employed in the optical scattering layer to increase optical extraction efficiency, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the complex scattering center structure from the optical scattering layer, replacing it with a simplified design that maintains light extraction efficiency while reducing device complexity. This is achieved by removing the minute structure scattering centers and using a more straightforward optical path control approach.
Solution Approach 2:
The patent changes the optical parameters of the scattering layer by adjusting the refractive index and thickness of the optical path control layer. By optimizing these parameters, the patent achieves effective light extraction without requiring complex scattering center structures, thus resolving the contradiction between efficiency and complexity.
2Loss of energy
If a multi-layered thin film structure is formed on the glass substrate to increase optical extraction efficiency, then light extraction efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and removes the complex multi-layered thin film structure (ITO/SiO2/TiO2) from the manufacturing process. By eliminating this complicated multi-layer deposition process, the patent simplifies manufacturing while maintaining optical extraction efficiency through the optimized optical path control layer with controlled refractive index and thickness.
Solution Approach 2:
The patent changes the manufacturing approach by focusing on controlling the refractive index and thickness parameters of a single optical path control layer rather than depositing multiple thin film layers. This parameter-based control simplifies the manufacturing process while achieving the desired optical extraction efficiency.
3Manufacturing precision
If different thicknesses of ITO layers are formed on reflection anode to improve color purity and efficiency, then color reproduction is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and eliminates the requirement for forming ITO layers with different thicknesses on the reflection anode. By removing this complex variable thickness deposition process, the patent simplifies manufacturing while maintaining color purity through the optimized optical path control layer that manages light extraction and color characteristics.
Solution Approach 2:
The patent changes the approach to color control by using a single optical path control layer with optimized refractive index and thickness parameters rather than requiring multiple ITO layers with different thicknesses. This parameter optimization achieves color purity while simplifying the manufacturing process.
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 optical path control layer significantly increases light emission efficiency, improving brightness and color reproducibility by optimizing the cavity length and reflectivity, achieving higher optical extraction efficiency and color purity compared to OLEDs without this layer.
Implementation Method 1
the color purity and efficiency were improved by employing a cavity effect in a top emission type OLED
Implementation Method 2
A difference between refractive indices of the optical path control layer and the transparent electrode may be no greater than 10% in the visible light region
Implementation Method 3
light having an incident angle greater than a critical angle at an interface of each of the layers cannot be emitted to the outside
Implementation Method 4
an optical scattering layer is included to increase optical extraction efficiency. In this technique, a scattering center having a minute structure is employed in a matrix of the optical scattering layer, and the optical extraction efficiency is increased through the scattering of light
Implementation Method 5
OLEDs are display devices that display an image using light emitted in processes of radiative recombination of excitons which are formed by combining holes supplied from an anode electrode with electrons supplied from a cathode electrode in the organic light emitting layer
Data Source
AI summary
Provided is an organic light emitting device (OLED) having increased optical extraction efficiency. The OLED includes a transparent substrate, an optical path control layer made of an optical transmittance material on the transparent substrate, a transparent electrode, an organic light emitting layer that generated light, and a reflection electrode formed on the organic light emitting layer, which are sequentially stacked. The refractive index And thickness of the optical path control layer are optimized.