Pixelated LED Phosphor Patterning to Reduce Optical Crosstalk
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Solution Overview
Problem
Decreasing pixel size and increasing pixel density in LED arrays lead to optical crosstalk due to light emission overlap, which is difficult to prevent with conventional photoresist patterning and phosphor deposition, especially in high-density micro-LED arrays, where die-to-die variation on wafers complicates accurate alignment and increases processing time and cost.
Innovation Solution
A self-aligned maskless method for manufacturing light sources with central patterned surfaces and unpatterned borders, where a down-converter material like phosphor is positioned within self-aligned cavities defined by light emission and photoresist removal, and light blocking metal is used between emitters to minimize crosstalk, allowing for precise control of light emission and color tunability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pixel size is decreased and pixel density is increased in LED arrays, then luminous efficacy and resolution are improved, but optical crosstalk between pixels increases due to light emission overlap
Solution Approach 1:
The patent divides the phosphor layer into multiple separated phosphor regions, each associated with discrete LED pixels. This segmentation prevents light from one pixel from exciting phosphor in adjacent pixel regions, thereby reducing optical crosstalk while maintaining high pixel density
Solution Approach 2:
The patent applies different properties to different regions: patterned surfaces with phosphor for light conversion and unpatterned borders without phosphor for light blocking. This local differentiation allows each pixel to maintain its optical independence while achieving high density
2Object-affected harmful factors
If conventional photoresist patterning and phosphor deposition are used to minimize optical crosstalk, then crosstalk reduction is achieved, but die-to-die variation on wafers complicates accurate alignment and increases processing time and cost
Solution Approach 1:
The patent employs self-aligned cavities formed by light emission from the LED pixels themselves to define phosphor deposition regions. The LED pixels automatically serve as the alignment reference for their own phosphor patterns, eliminating the need for external alignment procedures and reducing processing time
Solution Approach 2:
The patent pre-forms patterned surfaces and unpatterned borders on LED pixels before phosphor deposition. This preliminary structuring creates built-in alignment features that guide subsequent phosphor deposition, eliminating the need for time-consuming die-to-die alignment during manufacturing
3Manufacturing precision
If conventional photoresist patterning with precise alignment is used, then accurate phosphor positioning is achieved, but manufacturing cost increases due to time-consuming alignment procedures
Solution Approach 1:
The LED pixels themselves provide the alignment reference for phosphor deposition through self-aligned cavities. This self-referencing mechanism achieves precise phosphor positioning without requiring external alignment equipment or procedures, thereby reducing manufacturing cost
Solution Approach 2:
The patent combines the alignment reference function and the light emission function into the same LED pixel structure. The patterned surfaces and unpatterned borders serve both as optical elements and as alignment guides, eliminating the need for separate alignment features and reducing manufacturing complexity
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 approach effectively reduces optical crosstalk between LED pixels, enhances light extraction efficiency, and enables high-resolution, multicolor lighting with improved manufacturing efficiency and cost-effectiveness by eliminating the need for precise die-to-die alignment.
Implementation Method 1
a down-converter material, for example a phosphor material, on the semiconductor layer
Implementation Method 2
exposure of portions of a positive photoresist with light from the array of light emitters
Data Source
AI summary
A light source includes an array of light emitters, with at least some light emitters having a central patterned surface and an unpatterned border; a light blocking metal layer positioned between each of the array of light emitters; and down-converter material positioned on each of the array of light emitters.