Micro LED Reflective Pixel Structure for Higher External Quantum Efficiency
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Solution Overview
Problem
Micro light-emitting diodes (LEDs) face efficiency droop effects and damage during the etching process, leading to decreased external quantum efficiency (EQE) due to non-radiative recombination and increased carrier flow through sidewalls.
Innovation Solution
A display device with a substrate, a reflective structure, and a pixel unit is designed, where the reflective structure includes a first portion surrounding the light-emitting element and a second portion with a larger projected area on the substrate. This structure is formed through an electroplating process, improving electrical transmission and light-emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If etching process is used to manufacture micro LEDs, then micro LED structures can be formed, but sidewall damage is caused leading to non-radiative recombination and decreased external quantum efficiency
Solution Approach 1:
The patent removes the light-emitting layer from the sidewall region through selective etching, extracting the harmful portion where non-radiative recombination occurs. This leaves the sidewall without active light-emitting material, preventing carrier leakage and non-radiative recombination while maintaining the structural benefits of micro LEDs.
Solution Approach 2:
The patent applies different treatments to different regions: the top surface retains the complete light-emitting layer for efficient light emission, while the sidewall region has the light-emitting layer removed or modified. This local differentiation optimizes each region for its specific function - emission at the top, isolation at the sidewall.
2Illumination intensity
If current density is increased to improve light emission, then brightness increases, but efficiency droop occurs and external quantum efficiency decreases
Solution Approach 1:
The patent converts the potentially harmful sidewall region into a beneficial structure by removing the light-emitting layer from the sidewall. This transforms the sidewall from a source of non-radiative recombination into a purely reflective or isolating structure, allowing higher current densities to be applied without the penalty of efficiency droop.
3Area of stationary object
If micro LED size is reduced below 50 microns to increase pixel density, then display resolution improves, but sidewall surface area proportion increases causing greater carrier loss and decreased external quantum efficiency
Solution Approach 1:
By extracting the light-emitting layer from the sidewall region, the patent eliminates the mechanism of carrier loss that becomes increasingly significant as device size decreases. This allows micro LEDs below 50 microns to maintain high external quantum efficiency despite the increased proportion of sidewall surface 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
The proposed solution enhances the external quantum efficiency (EQE) of the light-emitting diodes by improving electrical transmission and light-emitting efficiency, thus addressing the efficiency droop and sidewall damage issues.
Implementation Method 1
The reflective structure includes a first portion and a second portion. The first portion of the reflective structure surrounds the light-emitting element... When the light-emitting element emits the light, since the first portion of the reflective structure surrounds the light-emitting element, it helps to improve an issue of poor electrical transmission and light-emitting efficiency
Implementation Method 2
A reflective structure is formed on the substrate through an electroplating process
Data Source
AI summary
A display device includes a substrate, a reflective structure, and a pixel unit. The pixel unit is disposed on the substrate. The pixel unit includes a sub-pixel. The sub-pixel includes a light-emitting element. A light emitted by the light-emitting element has a color. The reflective structure is disposed on the substrate. The reflective structure includes a first portion and a second portion. The first portion of the reflective structure surrounds the light-emitting element. A projection area of the first portion of the reflective structure on the substrate is less than a projection area of the second portion of the reflective structure on the substrate.