LED Light Extraction via Dual-Layer Refractive Index Control
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Solution Overview
Problem
Conventional light emitting devices suffer from low external quantum efficiency due to total internal reflection caused by the significant difference in refractive indices between semiconductor materials and air, limiting the extraction of light emitted from the active layer.
Innovation Solution
The implementation of a light emitting device with a semiconductor structure layer featuring a first lower refractive index layer and a second lower refractive index layer with roughness, where the second layer has a refractive index of 1.5 or less, and is composed of metallic oxide powders, to enhance light extraction efficiency by altering the critical angle of incident light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the refractive index difference between semiconductor and air is reduced, then light extraction efficiency is improved, but the critical angle for light emission increases
Solution Approach 1:
The resin layer serves as an optical intermediary that gradually transitions the refractive index from the semiconductor layer to air. This gradual transition allows light to be extracted over a wider angular range, effectively increasing the extraction efficiency while managing the critical angle constraint
2Productivity
If a rough surface is created on the semiconductor layer, then light extraction efficiency is improved, but manufacturing precision deteriorates
Solution Approach 1:
Instead of directly roughening the semiconductor layer surface, a resin layer is introduced as an intermediary that can be applied with controlled thickness and uniformity. The resin layer itself can be made rough or maintain a smooth interface, providing light extraction enhancement while preserving manufacturing precision and surface uniformity
Solution Approach 2:
A composite structure is formed by combining the semiconductor layer with a resin layer. This composite approach allows the resin to provide optical functions (reducing total internal reflection) while maintaining a controlled, precise interface with the semiconductor layer, thus achieving both improved light extraction and maintained manufacturing precision
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 configuration significantly improves external quantum efficiency and electrical reliability by effectively refracting and transmitting light, thereby increasing the extraction of photons from the semiconductor structure layer.
Implementation Method 1
a second lower refractive index layer having roughness disposed on the surface of the first lower refractive index layer and having a second refractive index lower than the first refractive index
Implementation Method 2
the second lower refractive index layer includes a plurality of metallic oxide powders
Data Source
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AI summary
Disclosed is a light emitting device (101) including a semiconductor structure layer (125) including a first conductive semiconductor layer (130), an active layer (140) on the first conductive semiconductor layer (130), and a second conductive semiconductor layer (150) disposed on the active layer (140), and a plurality of lower refractive layers (171,173) disposed on an outer surface of the semiconductor structure layer (125). The lower refractive layers includes a first lower refractive layer (171) having a first refractive index lower than a refractive index of the semiconductor structure layer (125) on a surface of the semiconductor structure layer (125), and a second lower refractive layer (173) having a second refractive index lower than the first refractive index on an outer surface of the first lower refractive layer (171), the second refractive index of the second lower refractive layer is 1.5 or less, the second lower refractive layer (173) is disposed on an outer surface thereof with a plurality of protrusions (31), and the second lower refractive layer (173) includes a plurality of metallic oxide powders.