LED with Uneven Doped Layers for Light Extraction
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Solution Overview
Problem
Conventional light emitting devices, such as Lambertian type LEDs, suffer from significant light loss due to absorption within the device, with approximately 80% of emitted light being trapped and absorbed, rather than being utilized effectively.
Innovation Solution
A light emitting diode (LED) design featuring a substrate with a light emitting layer comprising an N-type doped layer, a quantum well active layer, and a P-type doped layer, where at least one of the doped layers includes an uneven structure with ridges to concentrate light, and a reflective layer to redirect internal light back to the intended emitting direction, enhancing light utilization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional Lambertian type light emitting device is used, then light is emitted in all directions, but the majority of light (about 80%) is lost due to internal absorption
Solution Approach 1:
The patent introduces uneven layers with curved or non-planar interfaces between layers of different refractive indices. These curved interfaces act as optical elements that redirect light paths, converting the conventional Lambertian omnidirectional emission into a more directional beam. The curvature of the uneven layers focuses and directs light toward the intended emission direction, reducing internal absorption losses while maintaining ease of operation.
Solution Approach 2:
The patent changes the optical parameters by introducing layers with varying refractive indices and creating uneven interfaces with specific curvature radii. By adjusting the refractive index contrast and the geometry of the uneven layers, the light propagation characteristics are modified to reduce internal reflection and absorption, thereby improving light extraction efficiency without compromising operational simplicity.
2Productivity
If light is emitted in all directions in a conventional device, then omnidirectional coverage is achieved, but light utilization efficiency is poor with about 80% light loss
Solution Approach 1:
The uneven layers with curved interfaces redirect light that would otherwise be emitted in unintended directions back toward the intended emission direction. This curvature-based optical design increases the intensity of light in the desired direction by concentrating previously scattered light, thereby improving both light utilization efficiency and illumination intensity simultaneously.
Solution Approach 2:
The patent converts the harmful effect of internal light reflection and scattering into a beneficial effect. The uneven layers are designed to redirect internally reflected light back into the light emitting layer, where it can be re-emitted in the intended direction. This transforms what was previously wasted light (the harmful reflection) into useful light output, improving overall productivity and illumination intensity.
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 design significantly reduces internal light absorption and increases brightness by redirecting and focusing light emitted in unintended directions, thereby improving the overall light emission efficiency of the LED.
Implementation Method 1
a reflective layer disposed on a bottom surface of the substrate and a side wall of the light emitting diode, reflecting light towards the light emitting layer
Implementation Method 2
at least one of the N-type doped layer and the P-type doped layer comprises an uneven layer adapted to concentrate light emitting from the light emitting layer
Data Source
AI summary
The present application discloses a light emitting diode comprising a substrate; and a light emitting layer on the substrate. The light emitting layer comprises, an N-type doped layer; a quantum well active layer; and a P-type doped layer. At least one of the N-type doped layer and the P-type doped layer comprises an uneven layer adapted to concentrate light emitting from the light emitting layer.