Vertically Stacked LED Cells with Transparent Bonding Layer
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Solution Overview
Problem
There is a need for high-efficiency light emitting diodes (LEDs) that require combining multiple LEDs, but existing technologies struggle to effectively combine them to achieve high efficiency.
Innovation Solution
A light emitting device comprising two light emitting cells with a transparent bonding layer and electrical connections, where the second light emitting cell has an exposed surface for enhanced light output and is vertically stacked with the first cell to maximize active layer area, using a multi-step hole structure and electrical insulation for efficient electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple LEDs are combined to achieve high efficiency, then the overall light output and energy conversion efficiency are improved, but the device structure becomes more complex and difficult to manufacture
Solution Approach 1:
The patent combines multiple light emitting cells (first light emitting cell and second light emitting cell) into a single integrated device structure. The cells are vertically stacked and bonded together through a transparent bonding layer, creating a unified high-efficiency LED device that maintains improved light output while managing structural complexity through systematic integration
Solution Approach 2:
The patent transitions from a planar arrangement to a vertical three-dimensional stacking configuration. By arranging light emitting cells in the vertical dimension rather than side-by-side in a plane, the device achieves higher efficiency while optimizing space utilization and simplifying the overall structural layout
2Reliability
If metal pads are used for electrical connection, then reliable electrical contact is achieved, but metal pads obstruct the light path and reduce light extraction efficiency
Solution Approach 1:
The patent extracts and removes metal pads from the light output path. Instead of using traditional metal pads for electrical connection, the design eliminates these obstructive elements from the optical path while maintaining necessary electrical connections through alternative routing that does not interfere with light extraction
Solution Approach 2:
The patent introduces a transparent bonding layer as an intermediary material between the first and second light emitting cells. This transparent medium serves dual purposes: providing electrical connection pathways while simultaneously allowing light to pass through without obstruction, thus resolving the conflict between electrical reliability and light extraction efficiency
3Productivity
If the active layer area is increased to improve light output, then more light is generated, but the device footprint and manufacturing difficulty increase
Solution Approach 1:
The patent increases the effective active layer area by utilizing the vertical dimension through stacked cell configuration. Instead of expanding the device footprint horizontally, the design stacks multiple light emitting cells vertically, allowing increased light generation capacity within a compact footprint by exploiting the third dimension
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
This configuration enhances light extraction efficiency and allows for a series electrical connection of the cells, improving the overall efficiency and performance of the LED by maximizing active layer area and maintaining light output without metal pads obstructing the light path.
Implementation Method 1
A transparent bonding layer is located between the first light emitting cell and the second light emitting cell
Implementation Method 2
A first route metal is located on a sidewall of the hole and electrically coupled to the second semiconductor layer of the first light emitting cell and the first semiconductor layer of the second light emitting cell
Implementation Method 3
Each light emitting cell includes a first semiconductor layer, a second semiconductor layer, and an active layer between the first semiconductor layer and the second semiconductor layer
Implementation Method 4
the second semiconductor layer of the second light emitting cell has an exposed surface to serve as a light output surface
Data Source
AI summary
A light emitting device includes a first light emitting cell and a second light emitting cell. Each light emitting cell includes a first semiconductor layer, a second semiconductor layer, and an active layer between the first and second semiconductor layers. The second semiconductor layer of the second light emitting cell has an exposed surface. A transparent bonding layer is located between the first and second light emitting cells. A hole is formed on the first and second light emitting cells and the transparent bonding layer. A first route metal is located on a sidewall of the hole and electrically coupled to the second semiconductor layer of the first light emitting cell and the first semiconductor layer of the second light emitting cell. The active layer of the second light emitting cell has an area greater than the active layer of the first light emitting cell.