OLED Light Scattering Layer for Internal Light Extraction
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Solution Overview
Problem
Organic light-emitting display devices suffer from low outdoor visibility and luminescent efficiency due to internal light loss, with only 20% of emitted light being externally visible and 80% being lost within the device.
Innovation Solution
A light scattering layer is introduced between the organic layer and the pixel electrode, comprising particles from the residual layer of the pixel defining layer and a conductive layer with uneven protrusions formed using metal nano ink, which scatters light and improves visibility and efficiency across all wavelength bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional OLED structure is used, then the device structure is simple, but outdoor visibility and luminescent efficiency are low due to internal light loss
Solution Approach 1:
A light scattering layer is introduced as an intermediary component between the pixel electrode and the organic emission layer. This layer comprises scattering particles (such as TiO2, SiO2, or ZrO2) with a average particle size of 50-200 nm dispersed in a binder material, which mediates the light path to scatter internally generated light and extract more light from the device, thereby improving outdoor visibility without fundamentally redesigning the OLED structure
2Loss of energy
If a light scattering layer is added to improve light extraction, then outdoor visibility and luminescent efficiency are improved, but the device structure and manufacturing process become more complex
Solution Approach 1:
The light scattering layer is integrated into the existing OLED stack structure, merging the light scattering function with the existing pixel electrode and organic layer configuration. The scattering particles are incorporated into a binder material that forms a coherent layer, combining multiple functions (light scattering, electrical insulation, and structural support) into a single integrated component, thereby reducing the net increase in device complexity
Solution Approach 2:
The invention optimizes specific parameters of the light scattering layer to balance performance and complexity: the average particle size is controlled at 50-200 nm, the binder material has a refractive index of 1.4-1.7, and the layer thickness is maintained at 50-200 nm. These parameter optimizations ensure effective light scattering while maintaining compatibility with standard OLED manufacturing processes
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 light scattering layer enhances outdoor visibility and luminescent efficiency by scattering light generated in the organic layer, increasing the external emission of light and reducing internal loss, thereby improving the overall performance of the organic light-emitting display device.
Implementation Method 1
A light scattering layer is formed between the pixel electrode and the organic layer... the light scattering layer enhances outdoor visibility and luminescent efficiency by scattering light generated in the organic layer
Data Source
AI summary
An organic light-emitting display device including a thin film transistor (TFT) on a substrate; an organic light emitting diode (OLED) electrically connected to the TFT, the OLED including a pixel electrode, an organic layer, and an opposite electrode; a pixel defining layer (PDL) on the pixel electrode, the PDL including an opening that exposes at least one portion of the pixel electrode; and a light scattering layer between the pixel electrode and the organic layer.