LED Current Blocking Layer Design for Light Extraction
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Solution Overview
Problem
Light emitting devices (LEDs) suffer from reduced efficiency due to light absorption by electrodes, leading to heat generation and decreased service life, as a portion of emitted light is absorbed and not emitted outward.
Innovation Solution
A current blocking layer is formed using non-ohmic metals like titanium, zirconium, chrome, gold, or tungsten, which is separated from the heat treating process and material diffusion of the reflective layer, preventing current flow to the lower side of the electrode and enhancing light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a reflective layer is formed under the electrode to reflect light, then light emission efficiency is improved, but material diffusion during heat treating degrades the current blocking layer and reduces reliability
Solution Approach 1:
The patent divides the electrode structure into functionally separate layers: a reflective layer for light reflection and a current blocking layer for electrical isolation. This segmentation allows each layer to perform its specific function without interfering with the other, preventing material diffusion from degrading the current blocking properties while maintaining light reflection efficiency.
Solution Approach 2:
The patent introduces an intermediary barrier layer between the reflective layer and the current blocking layer. This intermediate layer prevents direct material diffusion between the two layers during heat treating processes, protecting the current blocking layer from degradation while allowing the reflective layer to maintain its light reflection function.
2Power
If electrodes are placed at both ends to apply power, then electrical functionality is achieved, but light absorption by electrodes generates heat and reduces service life
Solution Approach 1:
The patent converts the harmful light absorption by electrodes into a beneficial reflection process. By forming a reflective layer under the electrode, light that would otherwise be absorbed and converted to heat is instead reflected back through the active layer, enhancing light extraction efficiency and reducing harmful heat generation while maintaining electrical power application functionality.
Solution Approach 2:
The patent applies different material properties to different regions: the reflective layer has high reflectivity to redirect light, while the current blocking layer has high electrical resistance to block current. This local differentiation of material qualities allows the electrode structure to simultaneously achieve electrical functionality and minimize harmful light absorption effects.
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 increases light emitting efficiency by preventing light absorption and heat generation under the electrode, allowing for stable operation and improved optical efficiency of the LED.
Implementation Method 1
a current blocking layer which is not transformed into a layer to which a current can be injected through a heat treating process to form an ohmic layer
Data Source
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Figure 5
AI summary
A light emitting device including a second conductive type semiconductor layer; an active layer over the second conductive type semiconductor layer; a first conductive type semiconductor layer over the active layer; a second electrode in a first region under the second conductive type semiconductor layer; a current blocking layer including a metal; and a first electrode over the first conductive type semiconductor layer. Further, the first electrode has at least one portion that vertically overlaps the current blocking layer.