Microcavity LED Device with Unpatterned White Emitter
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Solution Overview
Problem
Existing LED devices face challenges in increasing light output, angular color performance, and manufacturability, with previous solutions often requiring complex patterned deposition technologies and suffering from significant light trapping and color shifts at different viewing angles.
Innovation Solution
A multi-color light-emitting microcavity LED device with an unpatterned white-light-emitting layer between a reflective and semi-transparent electrode, forming optical cavities that include multiple microcavities tuned to emit complementary wavelengths, and using color filters to create white sub-pixels that maintain color consistency across viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical cavity structures are employed to increase light output, then light emission is improved, but device complexity increases due to patterned deposition requirements
Solution Approach 1:
The patent segments the optical cavity into multiple discrete microcavities, each tuned to specific wavelengths. This allows the complex optical functionality to be divided into manageable units that can be implemented through simpler deposition processes, reducing overall device complexity while maintaining light output enhancement.
Solution Approach 2:
The patent employs parameter changes by tuning different microcavities to specific peak wavelengths (e.g., 480nm, 530nm, 610nm) to match the emission spectra of different organic materials. This wavelength-specific tuning achieves improved light output without requiring complex patterned deposition, as the optical properties are controlled through cavity geometry and material composition parameters.
2Ease of manufacture
If conventional LED structures are used, then manufacturing is simpler, but more than 50% of emitted light is trapped due to total internal reflection
Solution Approach 1:
The patent introduces a vertical dimension to light extraction by creating multiple microcavities at different positions and orientations within the device structure. This dimensional approach allows light to be extracted through multiple pathways and angles, overcoming the limitations of planar light extraction and reducing total internal reflection losses while maintaining manufacturing feasibility.
Solution Approach 2:
The patent employs optical spacers and cavity structures as intermediary elements between the organic light-emitting layer and the external environment. These intermediaries modify the optical path and enable light extraction that would otherwise be trapped, acting as mediators that convert internally trapped light into extractable output without complicating the base manufacturing process.
3Illumination intensity
If optical cavity devices are employed to enhance light emission, then light output increases, but angular color dependence becomes unacceptable
Solution Approach 1:
The patent applies local quality by creating different microcavity configurations at different locations within the device. Each microcavity is locally optimized for specific wavelength extraction, and the collective arrangement of these localized structures achieves broad-spectrum emission with reduced angular color dependence, as different regions contribute to different aspects of the overall emission profile.
Solution Approach 2:
The patent employs composite material structures combining multiple organic emitting materials with different emission spectra within the same device architecture. By integrating these composite materials with the multi-microcavity structure, the device achieves broadband emission that maintains color consistency across viewing angles, as the composite system compensates for angular variations through the combined emission of multiple wavelength components.
4Manufacturing precision
If color filters are used with optical cavity structures, then color control is improved, but device efficiency decreases due to light absorption
Solution Approach 1:
The patent extracts the color control function from traditional absorptive color filters and implements it through the optical cavity structure itself. By tuning the cavity resonances to specific wavelengths, the color selection is achieved through constructive and destructive interference rather than absorption, eliminating the energy loss associated with filter absorption while maintaining precise color control.
Solution Approach 2:
The patent substitutes the mechanical/chemical absorption mechanism of color filters with an optical interference mechanism based on microcavity resonance. This substitution replaces the lossy absorption process with a non-absorptive wavelength selection process, maintaining color control precision while dramatically reducing energy loss to absorption.
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 solution enhances light output, reduces angular color change, and improves manufacturability by employing an unpatterned white emitter with optical microcavities that emit complementary wavelengths, maintaining a consistent white appearance across angles and increasing overall device efficiency.
Implementation Method 1
a large fraction (e.g. greater than 50%) of the emitted light is trapped in the device due to total internal reflection
Implementation Method 2
optical cavity structures are known to increase the light emitted from an OLED device structure
Implementation Method 3
Light is emitted from a pixel when a current is passed through an organic material, the frequency of the light is dependent on the nature of the organic material used
Data Source
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AI summary
A white light-emitting microcavity light-emitting diode device, includes a reflective electrode (12) and a semi-transparent electrode (16) formed over a substrate and an unpatterned white-light-emitting layer (14) formed between the reflective electrode and the semi-transparent electrode, the reflective electrode, semi-transparent electrode, and unpatterned white-light-emitting layer forming an optical cavity. The reflective or semi-transparent electrode is patterned to form independently-controllable light-emitting sub-pixel elements (50, 52, 54, 56). Color filters (40R, 40G, 40B) are formed over a side of the semi-transparent electrodes opposite the unpatterned white light-emitting-layer in correspondence with the light-emitting elements to form colored sub-pixels. At least one light-emitting element has at least two commonly-controlled portions (56Y, 56B) to emit white light to form a white sub-pixel. The white sub-pixel includes optical microcavities (66Y, 66B) tuned to emit light at a different complementary wavelength at an emission angle.