Stacked Micro-LED Structure for Uniform RGB Brightness
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Solution Overview
Problem
Micro-LED displays face challenges in mounting and replacing micro-LEDs due to their small size, which affects brightness and visibility, particularly with red and green colors, requiring increased LED area or current density adjustments to compensate for brightness differences.
Innovation Solution
A light emitting diode stack with a stacked structure, including a support substrate, multiple LED stacks, and color filters, allows for increased luminous area without pixel area expansion, enabling simultaneous manufacturing of pixels and adjusting light emission based on visibility, with each LED stack emitting different colors independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If micro-LED area is increased to compensate for low visibility of red and green colors, then brightness uniformity improves, but pixel area increases
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of subpixels to a three-dimensional stacked structure where multiple LED stacks are arranged vertically. This dimensional change allows multiple color-emitting LEDs to occupy the same footprint area, thereby maintaining pixel area while achieving uniform brightness across different colors through the stacked configuration.
Solution Approach 2:
The patent implements a nested structure where multiple LED stacks (red, green, blue) are positioned within the same pixel footprint area. Each LED stack is vertically arranged and optically coupled to the substrate, allowing nested arrangement of multiple color-emitting elements without increasing the overall pixel area, thus resolving the contradiction between brightness uniformity and pixel area.
2Illumination intensity
If current density is adjusted to compensate for brightness differences, then brightness uniformity improves, but device complexity increases
Solution Approach 1:
The patent changes the structural parameters of the display by introducing multiple LED stacks with different emitting areas and configurations, rather than adjusting operational parameters like current density. By varying the physical structure (stacked arrangement, optical coupling) instead of electrical parameters, the patent achieves brightness uniformity while avoiding increased operating complexity.
3Productivity
If subpixel area is reduced to fit more subpixels in limited area, then display resolution improves, but brightness deteriorates
Solution Approach 1:
The patent resolves the contradiction between display resolution and brightness by moving from two-dimensional subpixel arrangement to three-dimensional stacked LED structures. Multiple LED stacks are vertically arranged within the same planar footprint, allowing high display resolution through dense packing while maintaining brightness through the stacked configuration that increases effective luminous area without increasing pixel area.
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 solution enhances brightness uniformity across colors, simplifies manufacturing, and maintains pixel area, improving luminous efficacy by preventing light interference and loss.
Implementation Method 1
a first color filter interposed between the first LED stack and the second LED stack and transmitting light generated from the first LED stack while reflecting light generated from the second LED stack
Implementation Method 2
a second color filter interposed between the second LED stack and the third LED stack and transmitting light generated from the first and second LED stacks while reflecting light generated from the third LED stack
Data Source
AI summary
A light emitting device including a first LED sub-unit having a thickness in a first direction, a second LED sub-unit disposed on a portion of the first LED sub-unit in the first direction, each of the first and second LED sub-units comprising a first-type semiconductor layer, a second-type semiconductor layer, and an active layer, a reflective electrode disposed adjacent to the first LED sub-unit and electrically connected to the first-type semiconductor layer of the first LED sub-unit, and a first ohmic electrode forming ohmic contact with the second-type semiconductor layer of the first LED sub-unit, in which the active layer of the first LED sub-unit is configured to generate light, includes AlxGa(1-x-y)InyP (0≤x≤1, 0≤y≤1), and overlaps the active layer of the second LED sub-unit in the first direction, and the active layer of the second LED sub-unit includes the same material as the active layer of the first LED sub-unit.