Vertical LED Stack Layout for Brighter High-Density Display Pixels
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Solution Overview
Problem
Micro LEDs in display apparatus face challenges in manufacturing due to their small size, making handling and mounting difficult, and the arrangement of sub-pixels within a limited area leads to reduced brightness due to smaller luminous areas.
Innovation Solution
The implementation of a light emitting diode (LED) stack with vertically stacked sub-pixels, including a support substrate, LED sub-units, and color filters, which allows for independent driving and reduces the surface area required for each sub-pixel, enabling simultaneous manufacturing on a wafer level and controlling brightness through a partial reflective layer and semiconductor bandgap manipulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If sub-pixels are arranged on a two-dimensional plane, then the display can implement various colors through mixed colors of blue, green, and red, but the area occupied by one pixel increases and the luminous area of each sub-pixel decreases
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of sub-pixels to a three-dimensional vertical stack configuration. Multiple LED sub-units emitting different colors (blue, green, red) are stacked vertically along the thickness direction, allowing light to pass through successive layers. This vertical stacking enables color mixing in the third dimension while maintaining a small footprint area, thereby increasing the luminous area of each sub-pixel without expanding the pixel area.
2Productivity
If micro LEDs are made with small form factor to increase density, then more micro LEDs can be disposed on one substrate, but handling and mounting becomes difficult
Solution Approach 1:
The patent combines multiple LED sub-units (blue, green, red) into a single integrated vertical stack structure that functions as one unified component. This merged stack can be handled and mounted as a single unit rather than individually handling each micro LED, significantly improving ease of operation during manufacturing while maintaining high density on the substrate.
3Productivity
If the area of each sub-pixel is reduced to fit more pixels in limited area, then more pixels can be arranged, but the brightness of sub-pixels deteriorates
Solution Approach 1:
The invention resolves this contradiction by moving the color mixing process from the horizontal plane to the vertical dimension. Multiple sub-units are stacked along the thickness direction with light paths arranged so that light from lower layers passes through upper layers. This enables high pixel density in the planar area while each sub-pixel maintains sufficient luminous area vertically, preserving brightness.
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 increases the light emitting area of each sub-pixel without increasing the pixel area, maintains display characteristics, and allows for efficient manufacturing and brightness control, addressing the challenges of handling and mounting micro LEDs.
Implementation Method 1
a first color filter interposed between the first LED sub-unit and the second LED sub-unit, and configured to transmit light generated in the first LED sub-unit and to reflect light generated in the second LED sub-unit
Implementation Method 2
a second color filter interposed between the second LED sub-unit and the third LED sub-unit, and configured to transmit light generated in the first and second LED sub-units and to reflect light generated in the third LED sub-unit
Data Source
AI summary
A light emitting diode (LED) pixel for a display including a first LED stack having a first well layer, a second LED stack disposed on the first LED stack and having a second well layer, a third LED stack disposed on the second LED stack and having a third well layer, a first electrode disposed on the first LED stack and in ohmic contact with the first LED stack, a second electrode disposed on the second LED stack and in ohmic contact with a surface of the second LED stack, and a third electrode in ohmic contact with a surface of the third LED stack, in which the first well layer includes at least one base material different from that of the second well layer.