LED Photonic Crystal Light Extraction Patterns
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face limitations in light extraction efficiency due to their structural design, which affects their luminance and ability to emit highly efficient white light, particularly in applications like displays and illumination devices.
Innovation Solution
The implementation of a photonic crystal structure with specific light extraction patterns on the conductive or non-conductive semiconductor layers, featuring distinct periods that optimize light extraction by enhancing transmittance beyond the critical angle, thereby improving light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED structural design is used, then manufacturing simplicity is maintained, but light extraction efficiency deteriorates
Solution Approach 1:
The patent applies porous photonic crystal structures to the LED device. The photonic crystal layer contains periodic porous patterns that create optical pathways for light extraction. This porous structure increases the extraction of guided modes and improves overall light extraction efficiency without complicating the manufacturing process, as the porous pattern can be formed through standard semiconductor fabrication techniques.
Solution Approach 2:
The patent introduces a periodic photonic crystal structure that adds spatial periodicity in the lateral dimension. This dimensional approach creates photonic bandgaps and modifies the density of optical states, enabling extraction of light that would otherwise be trapped in guided modes. The periodic modulation in the lateral dimension complements the vertical light extraction pathways.
2Illumination intensity
If light extraction structure is added to improve luminance, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The photonic crystal layer serves multiple functions simultaneously: it acts as a light extraction enhancement structure, a wavelength-selective optical filter, and a potential color conversion substrate. The periodic structure modifies the density of optical states to enhance extraction of specific wavelength ranges while maintaining structural integration with the LED device, thereby improving luminance without proportionally increasing complexity.
Solution Approach 2:
The porous photonic crystal structure provides multi-functionality by combining light extraction enhancement with wavelength selectivity. The periodic porous pattern creates photonic bandgaps that can be tuned to specific wavelength ranges, allowing the same structure to enhance luminance while potentially filtering or directing specific color components, thereby serving multiple optical functions in a single integrated layer.
3Loss of energy
If light extraction pattern periods are optimized for wavelength and refractive index, then light extraction efficiency is significantly increased, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the photonic crystal period parameter to satisfy the condition period > λ/n, where λ is the emission wavelength and n is the refractive index. This parameter optimization creates a photonic bandgap structure that enhances the extraction of guided modes. By carefully selecting the period parameter within this range, the structure achieves maximum light extraction efficiency while remaining compatible with standard fabrication tolerances.
Solution Approach 2:
The patent employs a periodic structure with period greater than the critical wavelength threshold (λ/n), which creates a photonic bandgap effect that significantly enhances light extraction. This excessive action of using periods larger than the minimum required scale creates a stronger photonic effect that improves extraction efficiency while being more tolerant to manufacturing variations, as the enhanced effect provides a margin of performance robustness.
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 described photonic crystal structure significantly increases light extraction efficiency, allowing for more effective transmission of light beyond the critical angle and higher optical power output, especially when the light extraction pattern periods are tailored to the wavelength and refractive index of the semiconductor materials used.
Implementation Method 1
a photonic crystal structure comprising a first light extraction pattern on the first conductive semiconductor layer having a first period, and second light extraction pattern on the first conductive semiconductor layer having a second period
Implementation Method 2
the first period being greater than λ/n, and the second period being identical to or smaller than λ/n, where n is a refractive index of the first conductive semiconductor layer, and λ is a wavelength of light emitted from the active layer
Data Source
AI summary
Provided are a light emitting device and a method of manufacturing the same. A light emitting device includes an active layer; a first conductive semiconductor layer on the active layer; a second conductive semiconductor layer on the active layer so that the active layer is disposed between the first and second conductive semiconductor layers; and a photonic crystal structure comprising a first light extraction pattern on the first conductive semiconductor layer having a first period, and second light extraction pattern on the first conductive semiconductor layer having a second period, the first period being greater than λ/n, and the second period being identical to or smaller than λ/n, where n is a refractive index of the first conductive semiconductor layer, and λ is a wavelength of light emitted from the active layer.