Photon Escape Layer Refractive Index Gradient for Light Extraction
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Solution Overview
Problem
Light emitting devices using nitride semiconductors have low light extraction efficiency, limiting their output.
Innovation Solution
A light emitting device with a photon escape layer having a refractive index between that of the light emitting structure and the encapsulating material, which increases the escape probability of photons by expanding their escape path through refraction or reflection, preventing internal scattering and providing a wider-angle escape path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional light emitting structure is used, then the device structure is simple, but the light extraction efficiency is low
Solution Approach 1:
A photon escape layer with intermediate refractive index (1.7-2.2) is introduced between the light emitting structure (refractive index 2.4-2.8) and the encapsulating material (refractive index 1.4-1.6). This intermediary layer reduces the refractive index difference at interfaces, minimizing total internal reflection and increasing photon escape probability from 30% to 70% or higher.
2Stability of the object's composition
If the refractive index difference between light emitting structure and encapsulating material is large, then the interface is well-defined, but photon escape probability is reduced due to internal scattering
Solution Approach 1:
The refractive index parameter of the photon escape layer is specifically optimized to fall within 1.7-2.2, which is higher than the encapsulating material (1.4-1.6) but lower than the light emitting structure (2.4-2.8). This parameter gradient approach creates optimal conditions for photon escape while maintaining clear interface definitions between layers.
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
Enhances the external quantum efficiency of light emission by increasing the probability of photons being emitted outside the device, thereby improving light extraction efficiency.
Implementation Method 1
the photon escape layer has a refractive index that is between a refractive index of the light emitting structure and a refractive index of an encapsulating material with respect to the light emitting structure such that an escape probability for photons emitted by the light emitting structure is increased
Implementation Method 2
expanding their escape path through refraction or reflection
Data Source
AI summary
A light emitting device including a light emitting structure having a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer; a first electrode on the light emitting structure; and a photon escape layer on the light emitting structure. Further, the photon escape layer has a refractive index that is between a refractive index of the light emitting structure and a refractive index of an encapsulating material with respect to the light emitting structure such that an escape probability for photons emitted by the light emitting structure is increased.