LED Device with Dual Optical Cavities for Light Extraction
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Solution Overview
Problem
LED devices face inefficiencies due to trapped light caused by high-index emissive materials and high manufacturing costs associated with patterned deposition techniques, particularly for large substrates, which limit light output and increase production expenses.
Innovation Solution
A light-emitting diode device structure featuring unpatterned light-emitting layers with two independently controllable optical cavities of different lengths, allowing for improved light extraction and reduced manufacturing complexity by using a common white-light-emitting layer with color filters to enhance color gamut and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If patterned deposition techniques are used to create color-specific light-emitting layers, then color accuracy is improved, but manufacturing cost and complexity increase significantly
Solution Approach 1:
The invention segments the color generation function into two separate components: (1) a single unpatterned white-light-emitting layer that emits all colors, and (2) color filters positioned in front of specific sub-pixels that select the desired color. This segmentation eliminates the need for complex patterned deposition of multiple color layers while maintaining color accuracy through the filter-based approach.
Solution Approach 2:
The invention extracts the color selection function from the light-emitting layer itself and places it in separate color filter components. Instead of embedding color-specific materials directly in the emissive layer through complex patterning, the color filtering function is taken out and implemented as discrete optical filters positioned in front of sub-pixels, thereby simplifying the deposition process.
2Loss of energy
If optical cavity structures are added to extract trapped light, then light output efficiency is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention merges the optical cavity function with the existing electrode and substrate structures. The reflective electrode serves dual purposes as both the electrical contact and the reflective surface of the optical cavity, while the substrate and encapsulation layers form the cavity boundaries. This integration eliminates the need for separate optical cavity components, reducing structural complexity while maintaining light extraction efficiency.
Solution Approach 2:
The reflective electrode performs multiple functions: it serves as the electrical contact for driving the OLED, provides the reflective surface for the optical cavity to extract trapped light, and contributes to the overall device encapsulation. This multi-functionality reduces the need for additional components and simplifies the overall device structure.
3Device complexity
If multiple color filters are used with unpatterned white emitter, then manufacturing cost is reduced, but light output efficiency decreases due to filter absorption
Solution Approach 1:
The invention converts the harmful effect of filter absorption into a beneficial outcome by using the optical cavity to pre-concentrate and direct light toward the filters at optimal angles. The cavity reflects and guides light so that filters receive more directed, concentrated light, improving their transmission efficiency and reducing the overall energy loss that would otherwise occur.
Solution Approach 2:
The optical cavity creates a feedback mechanism where light that would otherwise be lost through total internal reflection is redirected back into the light-emitting layer, giving it multiple chances to escape. This feedback loop increases the probability that light will reach the filters and be transmitted, compensating for the absorption losses in the filters.
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 increases light output, color gamut, and reduces manufacturing costs by minimizing trapped light and simplifying the deposition process, while maintaining or improving color accuracy and efficiency compared to prior art designs.
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
a reflective electrode and a second electrode formed over a substrate with an unpatterned light-emitting layer formed between the reflective electrode and the second electrode
Data Source
AI summary
A light-emitting diode device that includes a first group of sub-pixels each subpixel comprising a reflective electrode and a second electrode formed over a substrate with an unpatterned light-emitting layer formed between the reflective electrode and the second electrode, thus forming a first optical cavity having a first cavity length. Either the reflective or second electrode is patterned to form two or more independently-controllable, light-emitting sub-pixels. A second group of sub-pixels, each comprising a reflective electrode and a second electrode formed over the substrate. An unpatterned light-emitting layer is formed between the reflective electrode and the second electrode to comprise a second optical cavity having a second cavity length different from the first cavity length of the first optical cavity. Either the reflective or second electrode is patterned to form one or more independently-controllable, light-emitting sub-pixels.