Multi-Layer Reflector for LED Light Extraction
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Solution Overview
Problem
Existing light emitting devices, particularly III-nitride LEDs, suffer from light absorption within the device due to light being emitted or reflected in directions away from the emission surface, leading to reduced efficiency.
Innovation Solution
A reflective structure is integrated within the n-type region of the light emitting device, utilizing multiple layers of alternating high and low indices of refraction to reflect light back towards the light extraction region, enhancing light escape through a tuned reflector and potentially incorporating a wavelength converter structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light emitting layers emit light in all directions, then light coverage is comprehensive, but light absorption within the LED increases and efficiency decreases
Solution Approach 1:
The patent converts the harmful effect of light traveling in undesired directions (which causes absorption loss) into a beneficial effect by using a reflector to redirect this light toward the emission surface. The reflector captures light that would otherwise be lost and redirects it usefully, transforming the problem of omnidirectional emission into an advantage for light extraction efficiency.
Solution Approach 2:
The reflector acts as an intermediary element between the light emitting layers and the emission surface. It mediates the interaction by intercepting light traveling in undesired directions and redirecting it toward the emission surface, thereby improving light extraction without changing the fundamental omnidirectional emission characteristic of the LED.
2Loss of energy
If a reflector is added to redirect light, then light extraction efficiency improves, but device complexity increases
Solution Approach 1:
The reflector is designed to perform multiple functions: it redirects light toward the emission surface, provides structural support within the LED, and can be integrated with existing LED layers without requiring separate complex subsystems. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity.
Solution Approach 2:
The reflector's optical parameters (reflectivity, angle of reflection, spectral response) are optimized to achieve high light extraction efficiency. By carefully selecting and tuning these parameters, the reflector achieves effective light redirection with a relatively simple structure, avoiding the need for complex multi-element optical systems.
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 reflecting light emitted by the light emitting region back towards the extraction region, reducing absorption and enhancing the overall brightness of the device.
Implementation Method 1
The reflector can include multiple layers, where one layer has an index of refraction different than the other layers. The reflector being tuned to reflect light emitted by the light emitting region back toward the light extraction region.
Implementation Method 2
Light may be reflected within the LED, for example by total internal reflection at the interface between two materials with different indices of refraction.
Implementation Method 3
The reflector can include multiple layers, where one layer has an index of refraction different than the other layers.
Data Source
AI summary
Described is a reflector for light emitting devices. A device includes a reflector in contact with a first n-type region and a second n-type region. The reflector includes multiple layers. One layer having an index of refraction different than the other layers. The device includes a light emitting region (LER) in contact with the second n-type region, a p-type region in contact with the LER and a light extraction region (LXR) in contact with the p-type region. A majority of light escapes the device through the LXR. The reflector reflects light emitted by the LER back towards the LXR. In another device, a reflector is embedded in a n-type region of the device. The device includes a LER, a p-type region, and a wavelength converter structure. The reflector reflects light emitted by the wavelength converting structure back towards the wavelength converting structure.