Light Extraction Layer With Periodic Refractive Index For LED Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor light-emitting devices face light extraction efficiency losses due to refractive index differences between substrates and air, leading to incomplete light extraction, especially with high-refractive-index substrates, where light is reflected and cannot exit beyond the critical angle of total reflection.
Innovation Solution
A light-emitting device with a support substrate and a light transmission layer featuring a periodic refractive index distribution structure, comprising projections of a lower refractive index material than the substrate, which reduces the critical angle for total reflection and enhances light extraction efficiency by forming a layer with a resin material that undergoes phase transition upon energy beam irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a substrate with high refractive index is used, then the light emission intensity is improved, but the light extraction efficiency deteriorates due to total internal reflection at the substrate surface
Solution Approach 1:
The patent applies local quality by creating regions with different refractive indices within the light extraction layer. Specifically, it forms a light extraction layer containing particles with refractive index different from the resin matrix, creating local refractive index variations that enhance light extraction efficiency while maintaining overall high light emission intensity from the high-refractive-index substrate
Solution Approach 2:
The patent uses composite materials by combining resin matrix with dispersed particles having different refractive indices. This composite structure in the light extraction layer enables simultaneous achievement of high light emission intensity (from the substrate) and improved light extraction efficiency (through the composite layer's refractive index management)
2Loss of energy
If a nanometer-scale irregularity surface treatment is performed to improve light extraction efficiency, then the light extraction efficiency is improved, but the manufacturing complexity increases due to required etching processes
Solution Approach 1:
The patent replaces mechanical/chemical etching processes with a deposition-based approach. Instead of using complex etching to create surface irregularities, it forms a light extraction layer by depositing resin and particles, thereby achieving light extraction efficiency improvement while significantly reducing manufacturing process complexity
Solution Approach 2:
The patent changes the approach from modifying surface geometry (through etching) to controlling optical parameters (refractive index distribution) through material composition. By adjusting the refractive index of the light extraction layer materials rather than creating physical surface irregularities, it achieves light extraction enhancement with simpler manufacturing
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 significantly improves light extraction efficiency by increasing the critical angle for total reflection, allowing more light to be extracted from the device, as demonstrated by a four-fold increase in efficiency with the use of ZnO columns on GaN substrates.
Implementation Method 1
a resin layer on a support substrate including a light-emitting layer formed of a material having a property in which the refractive index of the resin layer is changed by a phase transition of the resin layer, and the phase transition occurs by irradiating the resin layer with an energy beam
Implementation Method 2
a light transmission layer, formed on the light extraction surface of the support substrate, having a periodic refractive index distribution structure in an in-plane direction and a thickness direction
Implementation Method 3
having a periodic refractive index distribution structure in an in-plane direction and a thickness direction, the light transmission layer including a plurality of projections formed of a material having a refractive index lower than that of the support substrate
Data Source
AI summary
A light-emitting device includes a support substrate which includes a light-emitting layer and a light extraction surface, and a light transmission layer, formed on the light extraction surface of the support substrate, having a periodic refractive index distribution structure in an in-plane direction and a thickness direction, the light transmission layer including a plurality of projections formed of a having a refractive index lower than that of the support substrate.