OLED Light Scattering Layer for Side-Emitting Light Extraction
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Solution Overview
Problem
Organic light emitting display apparatuses face challenges in maximizing light extraction efficiency and maintaining transparency, leading to reduced contrast and increased color shift phenomena due to the loss of side-emitted light and external light interference.
Innovation Solution
Incorporating a light scattering layer with scattering particles of 1 micrometer or smaller in the transmission region, which scatters incident light from the side surfaces while transmitting light from the top or bottom surfaces, and using a pixel defining layer to direct light to the scattering layer, enhancing light extraction and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light scattering layer is added to scatter side-emitted light, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
A light scattering layer is introduced as an intermediary component between the organic light emitting device and the external environment. This layer contains scattering particles that redirect side-emitted light toward the viewer, improving light extraction efficiency without requiring fundamental changes to the OLED structure itself.
Solution Approach 2:
The light scattering layer is formed as a composite material combining a transparent resin matrix with dispersed scattering particles (such as TiO2, SiO2, or ZrO2). This composite structure enables the layer to simultaneously maintain transparency for front-emitted light while scattering side-emitted light, resolving the contradiction between light extraction and device simplicity.
2Loss of energy
If the light scattering layer uses larger particles for stronger scattering, then light extraction efficiency improves, but color shift increases
Solution Approach 1:
The patent specifies controlling the particle size parameter within the range of 0.1 to 1.0 micrometers, with preferred ranges of 0.1 to 0.5 micrometers or 0.3 to 0.8 micrometers. This precise parameter control optimizes the balance between scattering efficiency and color shift, ensuring that particles are small enough to minimize color separation while large enough to effectively scatter side-emitted light.
3Illumination intensity
If the transmission region is made larger to improve transparency, then transparency improves, but light extraction efficiency decreases
Solution Approach 1:
The light scattering layer is strategically positioned and dimensioned to provide localized scattering functionality. By confining the scattering layer to specific regions with appropriate width and thickness parameters, the patent achieves effective light extraction enhancement without compromising the overall transparency of the transmission region, thus resolving the contradiction between these two opposing requirements.
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
Improves light extraction efficiency, increases contrast by utilizing side-emitted light, and reduces color shift by scattering light externally, achieving dual emission without pixel increase and maintaining transparency.
Implementation Method 1
a light scattering layer on the substrate and in the transmission region, and configured to scatter a light incident thereto from the intermediate layer
Implementation Method 2
excitons created when holes injected from the hole injection electrode and electrons injected from the electron electrode are combined in the organic light emission layer decay from excited states to a ground state and generate light
Data Source
AI summary
An organic light emitting display apparatus includes a substrate divided into a first light emission region, and a transmission region adjacent to the first light emission and through which an external light is transmitted, an organic light emitting device on the substrate and in the first light emission region, and including a pixel electrode, an intermediate layer on the pixel electrode and including an organic light emission layer, and an opposite electrode on the intermediate layer; and a light scattering layer on the substrate and in the transmission region, and configured to scatter a light incident thereto from the intermediate layer in the first light emission region.