LED Transparent Conductive Layer Holes for Light Extraction
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Solution Overview
Problem
Conventional LEDs experience reduced light extraction efficiency due to the absorption of light by the indium tin oxide (ITO) transparent conductive layer, which also limits current diffusion and uniformity, leading to unsatisfactory light emitting performance.
Innovation Solution
A transparent conductive layer with a reduced area is implemented by partially removing it and incorporating a plurality of holes at the region corresponding to the P-type electrode, allowing for electrical connection while minimizing light absorption and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the transparent conductive layer is made of ITO to promote current diffusion and enhance light emitting uniformity, then light emitting uniformity is improved, but light absorption increases and light extraction efficiency deteriorates
Solution Approach 1:
The patent extracts the transparent conductive layer from the region above the P-type electrode, removing it completely in this area to eliminate light absorption. The layer is retained only in peripheral regions where current diffusion is needed, thus taking out the harmful light-absorbing portion while preserving the useful current-diffusing portion.
Solution Approach 2:
The patent applies local quality by having the transparent conductive layer present in some regions (peripheral areas) and absent in others (above P-type electrode). This spatial variation in material presence allows different functional requirements to be met in different locations: current diffusion where the layer exists, and light transmission where it does not.
2Loss of energy
If the P-type electrode area is reduced to minimize light shielding, then light extraction efficiency is improved, but current concentration increases and light emitting uniformity deteriorates
Solution Approach 1:
The transparent conductive layer serves as an intermediary between the P-type electrode and the light emitting layer. It allows current to be delivered to the light emitting layer while its selective removal above the electrode enables light to pass through without being blocked by the opaque electrode, thus mediating between electrical conduction and optical transmission requirements.
3Loss of energy
If the transparent conductive layer area is reduced to minimize light absorption, then light extraction efficiency is improved, but current diffusion capability deteriorates
Solution Approach 1:
The patent extracts the transparent conductive layer from specific regions (above the P-type electrode) while retaining it in peripheral regions. This selective extraction minimizes light absorption in the critical light extraction path while preserving current diffusion capability in the peripheral areas where the layer remains.
Solution Approach 2:
The patent implements local quality by creating a non-uniform distribution of the transparent conductive layer across the device area. The layer is present in peripheral regions to provide current diffusion and absent in the central region above the P-type electrode to minimize light absorption, thus optimizing both functions in their respective locations.
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 partial removal of the transparent conductive layer increases light extraction efficiency by reducing absorption and promoting reflection, resulting in improved light emitting uniformity and brightness.
Implementation Method 1
ITO tends to absorb light. For the above structure, when the transparent conductive layer 8 is made of ITO, the diffusion of the current can be promoted to enhance the light emitting uniformity and efficiency, with however a considerable amount of light loss being resulted meantime as well.
Implementation Method 2
The reflecting layer 2 reflects the excited light 11 such that the excited light 11 exits via a same side in a concentrated manner.
Data Source
AI summary
A transparent conductive layer structure for an LED is provided. The LED includes a reflecting layer, an N-type electrode, an N-type semiconductor layer, a light emitting layer, a P-type semiconductor layer, a current block layer, a transparent conductive layer and a P-type electrode that are stacked on a substrate. The current block layer is disposed between and separates the P-type electrode and the P-type semiconductor layer. The transparent conductive layer is disposed between the P-type electrode and the current block layer, and connects to the P-type electrode and the P-type semiconductor layer. At a region corresponding to the P-type electrode, a plurality of holes are disposed at the transparent conductive layer to reduce an area of and hence an amount of light absorbed by the transparent conductive layer, thereby increasing light extraction efficiency of excited light from the light emitting layer and enhancing light emitting efficiency of the LED.