Transparent LED Submount Backside Light Extraction
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Solution Overview
Problem
High-power LEDs suffer from light loss due to internal reflections and absorption within the package, leading to reduced efficiency in converting electricity to light, as the light emitted from the active region is not effectively redirected for maximum output.
Innovation Solution
An LED assembly is designed with a submount made of optically transparent material, attached to the LED semiconductor, which provides an optical path for the generated light and includes a reflective coating to redirect backside light, optimizing the exposed surface area and reducing reabsorption, thereby enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light is emitted from the back side of the LED semiconductor, then the optical output can be increased, but light is lost due to internal reflections and absorption by the LED semiconductor
Solution Approach 1:
An optically transparent submount is introduced as an intermediary component between the LED semiconductor and the external environment. The submount provides an optimized optical path that allows backside-emitted light to escape efficiently while minimizing internal reflections and absorption losses within the semiconductor structure.
Solution Approach 2:
The refractive index parameters of the optical path are modified by introducing the transparent submount material with specific optical properties. This changes the light propagation characteristics, reducing total internal reflection at interfaces and improving light extraction efficiency from the LED semiconductor.
2Stability of the object's composition
If the LED semiconductor is mounted to a substrate, then the device structure is stabilized, but light emitted from the back side is lost unless redirected
Solution Approach 1:
The transparent submount serves multiple functions simultaneously: it provides mechanical support and structural stability like a traditional substrate, while also functioning as an optical element that guides and extracts light efficiently. This multi-functionality resolves the contradiction between structural stability and light output.
Solution Approach 2:
The submount acts as a mediator between the mechanical support function and the optical extraction function. It provides the necessary structural foundation for the LED semiconductor while simultaneously serving as an optical pathway that enables efficient light extraction from the back side.
3Productivity
If internal reflections occur at interfaces in the package, then light may be redirected, but absorption by the LED semiconductor reduces efficiency
Solution Approach 1:
The optical parameters at the semiconductor-package interfaces are modified by introducing the transparent submount with optimized refractive index. This reduces the refractive index mismatch at interfaces, minimizing total internal reflection and the associated light trapping and absorption effects within the semiconductor.
Solution Approach 2:
The potential harmful effect of internal reflections that typically trap light and cause absorption losses is converted into a beneficial effect. The transparent submount is designed to utilize interface reflections constructively to guide light toward efficient extraction paths rather than allowing random trapping and absorption within the semiconductor.
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 increases the total light output by minimizing internal reflections and absorption, improving the external quantum efficiency of the LED assembly compared to conventional designs.
Implementation Method 1
The LED semiconductor may include a p-type semiconductor and an n-type semiconductor forming a p-n junction defining an active region where light is generated
Implementation Method 2
The submount may include an optically transparent material... The light generated at the active region follows an optical path to the submount at the first surface
Implementation Method 3
Light emitted from a back side of the LED semiconductor may be lost unless redirected by a device package to reflect back and contribute to the output optical power
Data Source
AI summary
A light emitting diode (LED) assembly may include an LED semiconductor attached to a first surface of a submount made of optically transparent material. The submount may redirect back side light emitted by the LED semiconductor light away from the LED semiconductor to increase recovery of back side light. The submount may be used with an external bulk reflecting element. The submount may itself include a reflective coating at a second surface opposite from the first surface and be mounted on a reflecting substrate. The submount may include a phosphor forming the first surface or the second surface. The first surface or the second surface may be a textured surface. An array of LED semiconductors may be mounted to the submount. The array of LED semiconductors may be disposed on the submount in an arrangement that optimizes total light output of the LED assembly.