Inorganic LED Pixel Structure with Side Reflector for Light Extraction
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Solution Overview
Problem
Conventional inorganic LED displays face issues with light trapping and absorption due to the mismatch in optical refractive indices between semiconductor materials and substrates, leading to reduced emission efficiency and increased manufacturing costs, while existing black matrix structures can enhance contrast but also absorb emitted light and create viewing-angle dependence.
Innovation Solution
An inorganic LED pixel structure featuring a transparent pixel substrate with a reflector on its sides to direct emitted light outwards, combined with a black matrix between pixel structures to absorb ambient light, and micro-transfer printing for efficient mounting of LEDs, which includes a tether for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional inorganic LED displays are mounted on glass or polymer substrates, then the display can be manufactured with standard substrates, but more than 40% or even 50% of photons are trapped in the substrate due to refractive index mismatch and total internal reflection
Solution Approach 1:
The patent divides the substrate into multiple layers with different refractive indices (e.g., buffer layer, intermediate layer, and substrate layer) to gradually transition the optical impedance and reduce total internal reflection at single interfaces
Solution Approach 2:
The patent introduces intermediate layers with refractive indices between the semiconductor LED and the final substrate to act as optical mediators, reducing the abrupt refractive index mismatch that causes photon trapping
2Illumination intensity
If black matrix structures are added to improve display contrast by absorbing ambient light, then contrast is enhanced, but emitted light is also absorbed and viewing-angle dependence increases
Solution Approach 1:
The patent applies different optical properties to different regions: the black matrix is positioned only in non-emissive areas to absorb ambient light, while emissive pixel areas maintain high transmission and reflectivity properties to preserve emitted light
Solution Approach 2:
The patent incorporates light management structures that extend into the depth dimension (such as reflective layers and diffusive structures at various depths) to control light paths without requiring additional lateral space that would increase viewing angle dependence
3Loss of energy
If light management structures are added to improve light output from LEDs, then emission efficiency is enhanced, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent designs substrate layers that simultaneously serve multiple functions: mechanical support, electrical isolation, optical impedance matching, and structural alignment, thereby reducing the need for separate dedicated light management components
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 improves image quality and contrast by reducing light absorption and trapping, enhancing emission efficiency, and lowering manufacturing costs while maintaining mechanical and environmental robustness.
Implementation Method 1
light is often trapped in the semiconductor material due to total internal reflection and various light management structures are provided in LEDs to improve the light output
Implementation Method 2
light-absorbing layers internal to the display to reduce ambient light reflection
Data Source
AI summary
An inorganic light-emitting diode (iLED) pixel structure includes a transparent pixel substrate having an LED surface, an emission surface opposite the LED surface, and one or more sides other than the LED surface and the emission surface that are not parallel to the LED surface or the emission surface. One or more iLEDs are mounted on the pixel substrate and each iLED has an emission side adjacent to the LED surface of the pixel substrate to emit light into the pixel substrate and out of the emission surface. A reflector is disposed on at least a portion of the one or more sides.