Microlens LED Encapsulation for Higher Light Extraction
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Solution Overview
Problem
Existing optoelectronic devices with light-emitting diodes, such as microwires or nanowires, suffer from low light extraction efficiency due to a significant portion of photons not escaping and being absorbed or trapped by neighboring diodes.
Innovation Solution
The implementation of an optoelectronic device design featuring light-emitting diodes with encapsulation blocks that are at least partially transparent, air gaps between adjacent diodes, and an electrically conductive layer, along with a conformal dielectric layer and lenses to enhance light extraction, with refractive indices optimized to improve photon escape and directionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar LED structure with conventional encapsulation is used, then the manufacturing process is simple, but the light extraction efficiency is low due to total internal reflection at interfaces
Solution Approach 1:
The patent applies curvature by replacing the conventional planar LED structure with a microlens array where each lens has a curved spherical or hemispherical surface. This curvature eliminates total internal reflection at the semiconductor-encapsulation interface, allowing light to escape efficiently while maintaining a compact structure that can be manufactured using standard semiconductor processes.
Solution Approach 2:
The patent changes the geometric parameters of the LED structure by introducing microlenses with specific radii of curvature (R1, R2) and height (h). These parameter changes optimize the light extraction efficiency while controlling the emission angle and intensity distribution, transforming the light propagation characteristics without fundamentally altering the manufacturing approach.
2Loss of energy
If the encapsulation block thickness is increased to improve light extraction, then more light can escape, but the device size increases and manufacturing precision requirements increase
Solution Approach 1:
The curved microlens surface naturally guides light rays at optimal angles for extraction, eliminating the need for thick encapsulation layers. The spherical geometry provides inherent optical control that achieves high extraction efficiency with minimal encapsulation thickness, thereby reducing manufacturing precision requirements.
Solution Approach 2:
The patent applies different optical properties locally through the microlens array, where each lens is optimized for its specific function of extracting light from the underlying semiconductor region. This localized optimization allows efficient light extraction with thin encapsulation while maintaining overall device compactness.
3Loss of energy
If a high refractive index encapsulation material is used, then light extraction improves, but the mismatch with air causes increased total internal reflection
Solution Approach 1:
The microlens acts as an optical intermediary between the high refractive index semiconductor and the low refractive index air/encapsulation interface. The curved lens surface gradually transitions the light from the high-index medium, reducing the abrupt refractive index mismatch and minimizing total internal reflection at the final air interface.
Solution Approach 2:
The spherical microlens surface provides a gradual transition zone that manages the refractive index mismatch between materials. The curved geometry allows light to exit the semiconductor at optimized angles that avoid critical angles for total internal reflection, effectively mediating the optical transition between materials of different refractive indices.
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 significantly increases the light extraction efficiency and reduces light absorption by neighboring diodes, enhancing the overall performance of optoelectronic devices by improving the ratio of escaping photons and optimizing light emission directionality.
Implementation Method 1
in which the refractive index of the encapsulation block covering at least one of the light-emitting diodes is between 1.3 and 1.6
Implementation Method 2
light-emitting diodes (LEDs) resting on the face and comprising wire, conical or frustoconical semiconductor elements (16)
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
This description relates to an optoelectronic device (5) comprising a support (10) having a face (12); light-emitting diodes (LEDs) resting on the face and comprising wire, conical or frustoconical semiconductor elements (16); for each light-emitting diode, an encapsulation block (25) at least partially transparent to the radiation emitted by the light-emitting diodes and covering the light-emitting diode, the maximum thickness of the encapsulation block being between 1 µm and 30 µm, air gaps (37) being present between the encapsulation blocks covering adjacent diodes; and an electrically conductive layer (30) covering the encapsulation blocks, in which the refractive index of the encapsulation block covering at least one of the light-emitting diodes is between 1.3 and 1.6.