LED Light Extraction via Concave-Convex Passivation Structure
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Solution Overview
Problem
Light emitting diodes (LEDs) face inefficiencies in light extraction due to the refractive index mismatch between the semiconductor layer and air, leading to internal reflection and reduced external light emission, which can degrade electrical characteristics when conventional light extracting structures are employed.
Innovation Solution
A light emitting device with a concave-convex light extracting structure on a passivation layer surrounding the semiconductor layers, combined with electrode layers and a reflective layer, to enhance light extraction efficiency while maintaining electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a concave-convex light extracting structure is formed on the semiconductor layer to improve light extraction efficiency, then light extraction efficiency is improved, but electrical characteristics are degraded
Solution Approach 1:
The device is divided into distinct functional regions: a light extraction region with concave-convex structure for improving light extraction, and an electrode region with flat surface for maintaining electrical characteristics. This spatial segmentation allows each region to optimize its specific function without compromising the other.
Solution Approach 2:
Different surface structures are applied to different regions of the semiconductor layer. The light extraction region has a concave-convex structure to enhance light extraction efficiency, while the electrode region maintains a flat surface to ensure good electrical contact and characteristics. This local differentiation resolves the contradiction by applying the appropriate structure only where needed.
2Device complexity
If the semiconductor layer material has a lower refractive index than air to simplify device structure, then device structure is simplified, but light is totally reflected at the boundary surface and extinguished inside the semiconductor layer
Solution Approach 1:
A concave-convex curved structure is formed on the light extraction region of the semiconductor layer. This curvature modifies the boundary surface between the semiconductor layer and air, enabling light to be extracted at various angles and reducing total internal reflection, thereby improving light extraction efficiency while maintaining the simple device structure.
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
Improves light extraction efficiency and electrical characteristics of LEDs by effectively redirecting internal light outward without degrading the device's performance.
Implementation Method 1
light generated from the active layer is not effectively emitted to the outside, but totally reflected from a boundary surface and extinguished at an inside of the light emitting semiconductor layer
Implementation Method 2
a material constituting the light emitting semiconductor layer has a refractive index lower than that of external air
Data Source
AI summary
Disclosed is a light emitting device. The light emitting device includes a light emitting semiconductor layer including a first conductive semiconductor layer, an active layer on the first conductive semiconductor layer and a second conductive semiconductor layer on the active layer. A passivation layer is disposed on a surface of a light emitting semiconductor layer. A first electrode layer is disposed on the first conductive semiconductor layer and a second electrode layer is disposed on the second conductive semiconductor layer. Plurality of protrusion parts are disposed on a top surface of the first conductive semiconductor layer.