Patterned Remote Phosphor Crystal for LED Light Extraction
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Solution Overview
Problem
Conventional LED technologies face issues with heat dissipation, inconsistent phosphor thickness and density, and high light scattering due to the close proximity of phosphor to the LED chip, leading to reduced luminous efficacy and shortened lifespan, as well as high production costs and complexity in methods to improve light extraction efficiency.
Innovation Solution
A method involving the creation of orderly patterned remote phosphor crystal materials using laser ablation to form micro-structure arrays on the surface of Ce:YAG phosphor crystals, which enhances light extraction efficiency by reducing total internal reflection and increasing the probability of photon escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If phosphor is coated close to the LED chip, then the light extraction efficiency is improved, but the heat dissipation performance deteriorates and the chip temperature increases
Solution Approach 1:
The phosphor layer is segmented into multiple thickness zones with different phosphor concentrations. The region close to the LED chip has smaller phosphor particle concentration to reduce heat absorption, while the remote region has larger phosphor particle concentration to enhance light extraction efficiency. This spatial segmentation resolves the contradiction between light extraction and heat dissipation.
2Loss of energy
If phosphor particles are used, then the light scattering is reduced compared to powder, but the interface scattering between phosphor and carrier material causes significant light loss
Solution Approach 1:
Different regions of the phosphor layer have different phosphor particle concentrations and sizes. The local optical properties are optimized for each region: the region near the chip uses smaller particles with lower concentration to minimize scattering, while the remote region uses larger particles with higher concentration to maximize light extraction. This local quality variation reduces overall light loss.
3Ease of manufacture
If conventional spray or spin coating is used, then the phosphor can be applied to the LED chip, but the thickness and density of phosphor are inconsistent leading to poor product yield
Solution Approach 1:
The phosphor particles are pre-sorted by size before application, and the coating process is designed to deposit specific size ranges in specific regions. This preliminary preparation ensures that the phosphor layer achieves the desired non-uniform thickness and density distribution with high precision, improving product yield while maintaining manufacturing ease.
4Strength
If the refractive index difference between Ce:YAG and air is large, then the total internal reflection increases, but the light extraction efficiency decreases
Solution Approach 1:
The phosphor layer is extended in the vertical dimension with varying thickness and particle concentration. By controlling the phosphor distribution in the depth direction, light that would otherwise be trapped by total internal reflection at the surface can be gradually extracted as it propagates through the graded phosphor layer, converting a surface optical problem into a volumetric solution.
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 method significantly enhances the luminous efficacy of LEDs by increasing the front/side light emission ratio, simplifies the processing procedure, reduces production costs, and maintains the stability and mechanical strength of the crystal material, making it suitable for high-power white LED devices.
Implementation Method 1
focusing a short-pulse laser on a surface or above the surface of the remote phosphor crystal material ready for processing
Implementation Method 2
which forms micro-structure arrays on the surface of the remote phosphor crystal material
Data Source
AI summary
The present invention provide an orderly patterned remote phosphor crystal material and method for preparation the material and its application, which adopts short-pulse laser to make micro-structure arrays on the surface of phosphor crystal material to enhance the light extraction efficiency of the LED based on the material. The present invention overcomes the phosphor crystal material's properties of hard and dry/wet etching resistance and simplifies the processing steps, which accelerate the processing and improve the producing efficiency. The present invention is able to be performed under room temperature and environment friendly and the micro-structure is stable, which has broad application prospects in white LED field.