Microcavity LED Light Extraction via Segmented Reflectors
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Solution Overview
Problem
Existing LED devices face challenges in achieving high light output, manufacturability, and maintaining angular color performance due to issues with light trapping and angular dependence in optical cavity structures.
Innovation Solution
A thin-film, white-light-emitting diode device with a reflective and semi-transparent conductive thin-film structure forming two or more commonly-controlled microcavity structures, each emitting light with a smaller spectral range than the white-light-emitting layer, which reduces color change when viewed from different angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical cavity structures are used to increase light emission, then light output is improved, but angular color dependence increases
Solution Approach 1:
The optical cavity is segmented into multiple discrete reflective layers (first reflective layer, second reflective layer) with different optical properties. Each layer targets specific wavelength ranges, allowing the system to maintain broadband emission while reducing angular color dependence through distributed reflection paths
Solution Approach 2:
The patent employs a composite optical cavity structure combining multiple reflective materials with different characteristics. The first reflective layer (e.g., metal) and second reflective layer (e.g., dielectric stack) work together to create a broadband reflector that maintains stable color output across viewing angles while enhancing overall light extraction
2Power
If high-optical-index emissive materials are used, then light emission efficiency is improved, but light trapping increases
Solution Approach 1:
The patent introduces an optical cavity structure with multiple reflective layers as an intermediary between the high-optical-index emissive material and the external environment. This intermediary system manages the trapped light by providing controlled reflection paths, allowing efficient light extraction without sacrificing the benefits of high-index emissive materials
Solution Approach 2:
The optical cavity extends the light management in the vertical dimension with multiple reflective layers at different depths. This multi-layered approach creates additional light extraction pathways that overcome the light trapping effect of high-index materials while maintaining their emission efficiency
3Manufacturing precision
If patterned organic material deposition is used to form optical cavities, then color control is improved, but manufacturability decreases
Solution Approach 1:
The optical cavity structure serves multiple functions simultaneously: it provides color control through wavelength-selective reflection, enhances light extraction efficiency, and maintains manufacturability through a fabrication process compatible with existing OLED manufacturing techniques
Solution Approach 2:
The patent optimizes the optical cavity parameters (layer thicknesses, refractive indices, spacing) to achieve desired color control while maintaining compatibility with existing manufacturing processes. By carefully selecting parameters, the system achieves precise color tuning without requiring complex patterned deposition
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 increases light output and manufacturability while minimizing angular color change, providing a stable white light emission across various viewing angles.
Implementation Method 1
Each of the two or more microcavity structures has a different resonant frequency within one or more optical cavities and emits light with a smaller spectral range
Implementation Method 2
Because LED devices employ high-optical-index emissive materials, a large fraction (e.g. greater than 50%) of the emitted light is trapped in the device due to total internal reflection
Implementation Method 3
The thin-film layers emit white light in response to current provided by the conductive thin-film structure
Implementation Method 4
A first microcavity includes a first transparent spacer and a first mirror stack positioned on the first spacer to reflect light back into the OLED
Data Source
AI summary
A thin-film, white-light-emitting diode device includes a reflective, conductive thin-film structure and a semi-transparent, conductive thin-film structure. One or more thin-film layers are formed between the reflective and semi-transparent conductive thin-film structures to form two or more commonly-controlled microcavity structures. The thin-film layers emit white light in response to current provided by the conductive thin-film structure. Each of the two or more commonly-controlled microcavity structures has a different resonant frequency within one or more optical cavities and emits light with a smaller spectral range than the spectral range of the white-light-emitting thin-film layer(s). A combination of light emitted from the two or more commonly-controlled microcavity structures is white.