LED Reflective Structure with Cavities for Light Extraction
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face inefficiencies in light extraction due to internal total reflection, which limits their brightness and efficiency.
Innovation Solution
A light-emitting element with a reflective structure that includes a reflective layer, a first transparent layer, a window layer with a rough lower surface, and cavities within the transparent layers to reduce total reflection and enhance light extraction, utilizing materials like Indium-Tin Oxide and metal materials for electrodes and layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED structure is used, then device simplicity is maintained, but light extraction efficiency is limited due to internal total reflection
Solution Approach 1:
The device is segmented into multiple functional layers including a reflective layer, transparent layers with cavities, and a light-emitting stack. The cavity structure divides the transparent layer into regions with different optical properties, creating pathways for light extraction while maintaining overall device simplicity through systematic layering.
Solution Approach 2:
A reflective layer is introduced as an intermediary component between the light-emitting stack and the substrate. This reflective layer redirects internally reflected light back toward the light-emitting region, converting harmful total internal reflection into useful light extraction opportunities without complicating the overall device architecture.
2Loss of energy
If transparent layers with cavities and reflective layer are added, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The transparent layers serve multiple functions: they provide structural support, enable light transmission, and contain cavities that modify optical paths. The reflective layer simultaneously reflects light and provides a bonding interface between layers. This multi-functionality reduces the need for additional dedicated components, thereby limiting complexity growth despite improved light extraction.
Solution Approach 2:
The cavity structure is nested within the transparent layer, with the reflective layer nested at the bottom interface. This nested arrangement integrates multiple functional elements within a compact vertical stack, achieving complex optical functionality without proportionally increasing horizontal device footprint or manufacturing complexity.
3Illumination intensity
If internal total reflection is reduced, then brightness is improved, but manufacturing precision requirements increase
Solution Approach 1:
The optical parameters of the transparent layers are optimized by introducing cavities with specific geometries and distributions. By controlling cavity size, shape, and spacing parameters, the device achieves enhanced light extraction and brightness while maintaining manufacturability through well-defined geometric parameters that can be controlled using standard fabrication techniques.
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 structure increases light extraction efficiency by increasing the probability of light escaping the device rather than being reflected internally, leading to improved brightness and efficiency of the light-emitting element.
Implementation Method 1
A light-emitting device includes a reflective layer
Implementation Method 2
Conventional light-emitting diodes (LEDs) face inefficiencies in light extraction due to internal total reflection
Data Source
AI summary
A light-emitting device comprises a reflective layer; a first transparent layer on the reflective layer; a light-emitting stack comprising an active layer on the first transparent layer; and a cavity in the first transparent layer.