Top Emitting OLED Scattering Layers Microcavity Effect
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Solution Overview
Problem
Top emitting organic electroluminescent devices suffer from a microcavity effect that enhances emission at specific wavelengths while inhibiting others, which is detrimental for lighting applications requiring a full distribution of light intensity across the visible spectrum.
Innovation Solution
Incorporating a first scattering layer with 10-90% micro-particles and a second scattering layer in a top emitting organic electroluminescent device structure, which reduces and eliminates the microcavity effect, enhancing light extraction efficiency and maintaining a balanced light spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a top emitting device structure with bottom reflecting electrode and top translucent electrode is used, then emission at specified wavelength is enhanced and color purity is improved, but emission at non-specified wavelengths is inhibited causing microcavity effect
Solution Approach 1:
The patent applies scattering layers containing TiO2 particles to convert the harmful microcavity effect into beneficial light scattering. The scattering layers diffuse the light that would otherwise create microcavity resonance, transforming the problematic optical interference into enhanced light extraction and more uniform angular distribution of emitted light.
Solution Approach 2:
The scattering layers act as intermediary elements between the emitting layer and the external environment. These layers mediate the light extraction process by scattering photons multiple times, increasing the probability of light escaping the device while reducing the formation of microcavity modes.
2Illumination intensity
If microcavity effect is utilized to enhance emission at certain wavelength, then color purity and color gamut are improved, but full distribution of light intensity across visible spectrum is compromised
Solution Approach 1:
The patent applies scattering layers with specific optical properties at specific locations (near the emitting layer) to locally modify light extraction. This local modification enhances light extraction efficiency without significantly altering the spectral composition, thereby maintaining color purity while improving overall light output across the visible spectrum.
3Illumination intensity
If top emitting structure is used for display applications, then emission enhancement and color saturation are achieved, but light extraction efficiency is reduced for lighting applications
Solution Approach 1:
The scattering layers convert the harmful effect of total internal reflection and waveguide modes into beneficial light scattering. By introducing TiO2 particles with high refractive index, the patent creates multiple scattering events that increase the optical path length and extraction probability, thereby improving light extraction efficiency while maintaining the top-emitting structure's color saturation benefits.
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 solution effectively reduces the microcavity effect, enhancing light extraction efficiency and achieving a light spectrum similar to bottom emitting devices, with devices having a first scattering layer with silica content above 10 wt% showing significant improvement in light distribution and reduced optical interference.
Implementation Method 1
the first scattering layer and the second scattering layer create more new directions in which light travels
Data Source
AI summary
The present disclosure provides a top emitting organic electroluminescent device including a first scattering layer, and a first electrode, at least one organic material layer, a second electrode and a second scattering layer formed on the first scattering layer sequentially. The first scattering layer contains a plurality of micro-particles that are 10 to 90 wt % of the first scattering layer.