OLED Light Extraction via Intermediary Scattering Layer
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Solution Overview
Problem
Conventional organic light-emitting diodes (OLEDs) face inefficiencies in light coupling due to wave guide effects, resulting in limited light output and inhomogeneous luminous density, particularly as distance from electrical contacts increases, with existing solutions either reducing efficiency or altering the OLED's appearance.
Innovation Solution
Incorporating an optical scattering layer with a higher refractive index than the substrate or cover layer, arranged between the transparent electrode and the organic light-emitting layer, to enhance light coupling and homogenize luminous density by varying scatter particle concentration or thickness, allowing targeted light emission and compensation for inhomogeneities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If scattering films or surface structures are applied to the substrate outer side to couple out light, then light coupling efficiency is improved, but the appearance of the OLED is significantly influenced by producing a milky, diffusely reflecting surface
Solution Approach 1:
The patent introduces an optical scattering layer as an intermediary component between the substrate and the transparent electrode. This scattering layer couples out light from wave guide modes while maintaining a planar outer surface that preserves the OLED's appearance. The scattering layer mediates between the need for light extraction and the need for aesthetic appearance, solving the contradiction by providing light coupling functionality without producing a milky surface.
2Area of stationary object
If the distance from electrical contacts increases in large-area OLEDs, then manufacturing scalability is improved, but light density inhomogeneity increases
Solution Approach 1:
The patent implements local quality by varying the optical properties of the scattering layer across different regions of the OLED. Specifically, the scattering strength or thickness of the scattering layer is adjusted in different areas to compensate for the natural decrease in light density away from electrical contacts. This local variation in the scattering layer's properties ensures uniform luminous density across the entire large-area OLED, solving the inhomogeneity problem while maintaining scalability.
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 scattering layer effectively increases light coupling efficiency and homogenizes luminous density, improving the OLED's performance by enhancing light emission and allowing for structured luminous impressions, such as writing or symbols, while maintaining a clear appearance.
Implementation Method 1
at least one optical scattering layer, in each case arranged on a side of the transparent electrode facing away from the organic light-emitting layer
Implementation Method 2
The organic functional layer stack has an organic light-emitting, electroluminescent layer
Data Source
AI summary
An organic light-emitting device includes a substrate, on which a transparent electrode and a further electrode are applied. An organic light-emitting layer is arranged between the electrodes. At least one optical scattering layer is arranged on a side of the transparent electrode facing away from the organic light-emitting layer.