OLED Microcavity Light Emitting Device for High Efficacy White Light
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Solution Overview
Problem
Current white light organic light emitting diode (OLED) devices have low luminous power efficacy due to the inability to optimize light output for multiple colors simultaneously using double resonant cavity structures, which improves efficiency for one color but reduces radiance in others.
Innovation Solution
The device comprises groups of stripe-shaped OLEDs with a first microcavity and a second microcavity between the second electrode layer and the carrier substrate, using a layer sequence of lower and higher index layers to enhance light outcoupling, combined with a diffuser or scattering element to mix colors and reduce angle-dependent effects, allowing independent optimization of each color's efficacy without reducing radiance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a double resonant cavity structure is applied to optimize light output for one color, then the luminous power efficacy for that color is improved, but the radiance of other colors is reduced
Solution Approach 1:
The device is divided into multiple independent OLED groups, each with its own double resonant cavity structure optimized for a specific color wavelength. This segmentation allows each color to have its own optimized cavity without interfering with other colors, thereby improving luminous power efficacy for each color while maintaining radiance across the full spectrum.
Solution Approach 2:
Each OLED group has locally optimized cavity structures with specific layer thicknesses and refractive indices tailored to its designated color wavelength. The first microcavity and second microcavity parameters are locally adjusted for each color (red, green, blue) to maximize light outcoupling efficiency at that specific wavelength while preserving performance at other wavelengths.
2Adaptability or versatility
If multiple OLEDs emitting different colors are combined in one layer stack to provide white light, then white light emission is achieved, but the luminous power efficacy is reduced
Solution Approach 1:
Instead of combining different color layers in a single stack, the invention segments the white light generation into multiple independent OLED groups arranged in an array. Each group emits a specific color with optimized cavity structures, and the combined output produces white light. This segmentation allows each OLED to operate at high efficiency for its specific color while achieving overall white light emission.
Solution Approach 2:
The invention transitions from a vertical stacking approach (multiple layers in one stack) to a spatial array approach (multiple OLED groups arranged side by side). This dimensional change from 1D stacking to 2D/3D arrangement allows independent optimization of each color channel while maintaining compact white light emission capability.
3Loss of energy
If a tuned microcavity structure is applied to increase light output into air, then the light coupling efficiency is improved by about 50%, but the overall efficiency remains too low for effective lighting applications
Solution Approach 1:
The invention implements a nested dual microcavity structure where a first microcavity (between electrodes) and a second microcavity (between second electrode and substrate) are nested within each other. This nested configuration creates multiple resonant conditions that work together to dramatically enhance light outcoupling efficiency, pushing the overall efficiency into the range needed for effective lighting applications.
Solution Approach 2:
The invention systematically optimizes multiple parameters including the thickness and refractive index of layers in both microcavities, the spacing between OLED groups, and the optical properties of the substrate. By changing these parameters to create dual resonant conditions, the light coupling efficiency is enhanced beyond the 50% improvement of single cavity structures to achieve overall efficiency suitable for lighting applications.
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 approach significantly increases the lumen output of the device, with the luminous power efficacy of each color being more than doubled compared to single resonant cavity OLEDs, achieving a high luminous power efficacy for white light emission while maintaining color balance.
Implementation Method 1
a first layer sequence including at least an organic layer or layer stack between a first and a second electrode layer, said first and said second electrode layers forming a first microcavity
Implementation Method 2
At least one of the organic light emitting diodes of each group comprises a second layer sequence forming a second microcavity between the second electrode layer and the carrier substrate
Implementation Method 3
The second layer sequence comprises at least a lower index layer between two higher index layers
Implementation Method 4
A diffuser or scattering element is arranged in an emission direction of the organic light emitting diodes in front of the carrier substrate, said element mixing the light of said different colors of each group leaving the carrier substrate
Data Source
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Figure 3~4
AI summary
The present invention relates to a light emitting device comprising several groups of stripe shaped organic light emitting diodes (15, 16, 17) arranged side by side on an optically transparent carrier substrate (4). The organic light emitting diodes (15, 16, 17) comprise a first layer sequence (2) forming a first microcavity. At least one of the organic light emitting diodes (15, 16, 17) of each group comprises a second layer sequence (3) forming a second microcavity between the second electrode layer (5) and the carrier substrate (4). The second microcavity is adapted in thickness of at least one of its layers to increase light out put of the corresponding organic light emitting diode (15, 16, 17). A scatter or diffuser element (14) is arranged in an emission direction of the organic light emitting diodes (15, 16, 17) in front of the carrier substrate (4), to mix the light of said different colors of each group leaving the carrier substrate. The present device allows the emission of white light with a high efficacy.