Micro-LED Color Conversion Layers for Light Extraction and Phosphor Life
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Solution Overview
Problem
The production of color conversion devices is hindered by manufacturing challenges such as the shortening of phosphor lifetimes due to heat generated by excitation sources and inefficient processes requiring separate pixel fabrication and binning.
Innovation Solution
The development of light-emitting pixels for LED-based displays, which include a substrate with red, green, and blue sub-pixels. Each sub-pixel features a light-emitting diode, a coupling layer with scattering particles, and a light-emission layer containing quantum dots in a polymeric matrix. This design enhances light coupling and extraction while shielding heat-sensitive phosphors from heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphors are placed close to the excitation source for efficient light conversion, then light conversion efficiency is improved, but phosphor lifetime is shortened due to heat exposure
Solution Approach 1:
A coupling layer is introduced as an intermediary component between the excitation source and the phosphor layer. This coupling layer mediates the optical interaction while providing thermal isolation, allowing efficient light coupling without direct thermal exposure of the phosphor to the excitation source heat.
Solution Approach 2:
The harmful thermal effect is extracted and separated from the optical coupling function. The coupling layer performs the optical coupling function while the phosphor layer is thermally isolated, effectively removing the harmful thermal interaction while maintaining optical efficiency.
2Adaptability or versatility
If separate pixel fabrication processes are used for red, green, and blue sub-pixels, then manufacturing flexibility is improved, but production efficiency is reduced due to binning requirements
Solution Approach 1:
The fabrication processes for red, green, and blue sub-pixels are merged into a single integrated process. All three sub-pixel types are fabricated simultaneously on the same substrate using the same sequence of steps, eliminating the need for separate fabrication lines and subsequent binning operations.
Solution Approach 2:
A universal fabrication process is developed that can manufacture all three sub-pixel types (red, green, blue) using the same methodology. The process uses universal materials and steps that work for all color conversions, making the manufacturing line adaptable to produce any combination of sub-pixels without reconfiguration.
3Device complexity
If flat interfaces are used between LED and light-emission layer, then device complexity is reduced, but light extraction efficiency is poor due to internal reflection
Solution Approach 1:
The flat interface between the LED and light-emission layer is replaced with a curved interface formed by a dome-shaped coupling layer. This curvature changes the angle of light incidence at the interface, reducing internal reflection and improving light extraction efficiency while adding minimal structural complexity.
Solution Approach 2:
The interface geometry is changed from two-dimensional (flat plane) to three-dimensional (dome shape). This dimensional change introduces a curved surface that optimizes light extraction angles and reduces internal reflection, transforming a simple planar interface into an optimized optical interface.
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 solution prolongs the useful lifetime of heat-sensitive phosphors, reduces manufacturing complexity by eliminating the need for binning, and improves light extraction and uniformity, leading to more efficient and durable color conversion displays.
Implementation Method 1
a first coupling layer disposed over the first light-emitting diode
Implementation Method 2
a red light-emission layer comprising red-emitting quantum dots
Data Source
AI summary
Light-emitting sub-pixels and pixels for micro-light-emitting diode-based displays are provided. Also provided are methods of fabricating individual sub-pixels, pixels, and arrays of the pixels. The sub-pixels include a double-layered film that includes a coupling layer disposed over a light-emitting diode and a light-emission layer disposed over the coupling layer.