Micro-LED Chip Sidewall Reflection for Forward Light Output
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Solution Overview
Problem
Micro-light-emitting diode chips experience significant light leakage from their side surfaces due to the increased total area after miniaturization, leading to a decrease in forward-directed light emission after packaging, as the refractive index difference between the chip and the external environment is reduced.
Innovation Solution
A micro-light-emitting diode chip design incorporating an epitaxial structure, a transparent structure with an inclined or curved surface, and a reflection layer, where the transparent structure is positioned on the sidewall and the reflection layer is in direct contact with the outer surface, effectively reflecting lateral light towards the forward direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the chip size is miniaturized, then the pixel density and resolution are improved, but the total side surface area increases leading to greater light leakage
Solution Approach 1:
The patent converts the harmful light leakage from the side surface into beneficial forward-directed light by applying a reflection layer to the side surface. This reflection layer reflects the laterally emitted light back toward the forward direction, transforming the energy loss into useful light output that enhances the overall brightness and efficiency of the miniaturized chip.
Solution Approach 2:
The patent applies different functional properties to different parts of the chip structure. Specifically, the side surface is given reflective properties through the reflection layer, while the top surface maintains its light-emitting function. This local differentiation allows the side surface to contribute positively to forward light output rather than merely leaking light.
2Measurement precision
If the chip size is reduced, then the display resolution is improved, but the amount of light emitted in the forward direction decreases
Solution Approach 1:
The reflection layer on the side surface captures light that would otherwise be lost and redirects it toward the forward direction. This increases the overall forward light emission from miniaturized chips, ensuring that even as chip size decreases for higher resolution, the brightness and illumination intensity are maintained or enhanced.
Solution Approach 2:
The patent merges the light-emitting function with the side surface by adding the reflection layer. Instead of the side surface being purely a structural boundary that leaks light, it becomes an active light-redirection component that contributes to the overall light output, effectively combining multiple functions in a miniaturized structure.
3Reliability
If the refractive index difference between chip and external environment is reduced after packaging, then the packaging integrity is improved, but light reflection and forward emission are reduced
Solution Approach 1:
The reflection layer compensates for the reduced light reflection caused by lower refractive index difference after packaging. By actively reflecting lateral light toward the forward direction, it maintains high forward light emission even when the passive optical contrast between chip and packaging material is reduced, ensuring packaging integrity does not come at the cost of light output.
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 design enhances the brightness of light emitted in the forward direction by redirecting lateral light, thereby increasing the overall light output from the micro-light-emitting diode chip.
Implementation Method 1
The reflection layer is in direct contact with the outer surface... effectively reflecting lateral light towards the forward direction
Implementation Method 2
The transparent structure has an inner surface and an outer surface opposite to the inner surface... redirecting lateral light
Data Source
AI summary
A micro-light-emitting diode chip includes an epitaxial structure, an electrode, a transparent structure, and a reflection layer. The epitaxial structure has a light exit surface, a back surface opposite to the light exit surface, and a sidewall surface. The sidewall surface is connected to the light exit surface and the back surface. The electrode is electrically coupled to the epitaxial structure. The transparent structure has an inner surface and an outer surface opposite to the inner surface. The inner surface is connected to the sidewall surface. A distance between the outer surface and the inner surface on a plane where the back surface is located is less than a distance between the outer surface and the inner surface on a plane where the light exit surface is located. The reflection layer is in direct contact with the outer surface. A micro-light-emitting diode display is also provided.