OEL Lighting Element Array Scattering Layer Design
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Solution Overview
Problem
Organic electroluminescent (OEL) lighting element arrays face issues with voltage drop and total internal reflection, leading to uneven brightness and reduced external quantum efficiency when illuminating large areas, particularly due to the use of transparent conductive materials like ITO which cause dark zones and light obstruction.
Innovation Solution
The implementation of a patterned scattering layer with a higher refraction index than the transparent electrodes, combined with auxiliary electrodes and a patterned dielectric layer, scatters lateral light emitted from OEL layers, allowing it to pass through the substrate and reducing dark zones, thereby enhancing external efficiency and uniformity of light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent conductive materials (ITO) are used for electrodes to maintain transparency, then light transmission is improved, but voltage drop (IR drop) increases leading to uneven brightness
Solution Approach 1:
The electrode structure is segmented into multiple components: transparent conductive layers (ITO, IZO, or AZO) for light transmission, auxiliary transparent conductive layers for voltage compensation, and reflective layers for light redirection. This segmentation allows each layer to perform its specialized function, resolving the contradiction between transparency and voltage uniformity.
Solution Approach 2:
The patent changes the optical parameters of the electrode structure by introducing layers with different refraction indexes. The auxiliary transparent conductive layers have refraction indexes matched to adjacent layers, reducing total internal reflection. Reflective layers have high reflectivity to redirect light. These parameter changes enable both good light transmission and voltage uniformity.
2Reliability
If metal mesh is added to resolve voltage drop, then brightness uniformity is improved, but light transmission is blocked creating dark zones
Solution Approach 1:
The patent replaces the traditional metal mesh with transparent conductive materials (ITO, IZO, or AZO) that are deposited as thin films. These transparent electrodes provide the necessary electrical conductivity for voltage uniformity while maintaining optical transparency, effectively substituting a blocking structure with a transparent alternative.
Solution Approach 2:
The electrode structure uses composite material design combining transparent conductive oxides (ITO, IZO, AZO) with reflective layers. This composite structure achieves both electrical functionality (voltage uniformity) and optical functionality (light transmission) without the dark zones created by metal meshes.
3Power
If transparent conductive materials with high refraction index are used, then electrode conductivity is improved, but total internal reflection increases reducing external quantum efficiency
Solution Approach 1:
The patent introduces auxiliary transparent conductive layers as intermediary elements between the transparent electrode and the OEL layer. These intermediary layers have refraction indexes that are matched to adjacent layers, serving as optical mediators that gradually transition the light from high refraction index to low refraction index, thereby reducing total internal reflection and improving external quantum efficiency.
Solution Approach 2:
The patent systematically changes the refraction index parameters across different layers. The auxiliary transparent conductive layers are specifically designed with refraction indexes that match adjacent layers, creating a gradient that minimizes optical reflection losses while maintaining the high conductivity of the transparent electrode.
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 significantly reduces non-illuminative regions and achieves satisfactory external efficiency by scattering light that would otherwise be lost due to total internal reflection, ensuring even and uniform light emission across the illumination area.
Implementation Method 1
the refraction index of the transparent conductive material including ITO is greater than the refraction index of the substrate which carries the OEL lighting element, and light obliquely emitted from the anode to the substrate is likely to encounter total internal reflection (TIR) due to the difference in the refraction indexes of different materials
Implementation Method 2
The patterned scattering layer is disposed among the first electrodes on the substrate and located on edge portions of the first electrodes... scatters lateral light emitted from the OEL layers
Data Source
AI summary
An organic electroluminescent (OEL) lighting element disposed on a substrate includes a first electrode, a second electrode, an OEL layer, an auxiliary electrode, a patterned scattering layer, and a patterned dielectric layer. The second electrode is opposite to the first electrode having a first refraction index. The OEL layer is disposed between the first electrode and the second electrode. The auxiliary electrode is disposed between the first electrode and the second electrode, electrically connected to the first electrode, and separated from the OEL layer by a gap. The patterned scattering layer is disposed between the first electrode and the auxiliary electrode, covers the auxiliary electrode, and has a second refraction index greater than or substantially equal to the first refraction index. The patterned dielectric layer is disposed between the auxiliary electrode and the second electrode, covers the auxiliary electrode, and is disposed between the auxiliary electrode and the OEL layer.