LED Light Extraction via 3D Nano-Structures
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Solution Overview
Problem
The efficiency of conventional light emitting diodes (LEDs) is limited by the high refractive index of the P-type and N-type semiconductor layers, leading to low external quantum efficiency.
Innovation Solution
The development of a light emitting diode (LED) with a second semiconductor layer featuring three-dimensional nano-structures that enhance light extraction efficiency by transforming light with large incidence angles into light with smaller angles, thereby improving the overall light extraction intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED structure with planar semiconductor layers is used, then manufacturing is simple, but light extraction efficiency is low due to high refractive index
Solution Approach 1:
The patent transforms the planar two-dimensional semiconductor layer into a three-dimensional nano-structured layer with protrusions and recesses. This dimensional change creates multiple light extraction interfaces and paths, enabling light at large incidence angles to be converted to smaller angles through the nano-structures, thereby significantly improving light extraction efficiency without complicating the manufacturing process
Solution Approach 2:
The patent modifies the surface morphology parameter of the semiconductor layer by introducing three-dimensional nano-structures with specific height ranges (100-500 nm) and density distributions. This parameter change alters the optical properties at the semiconductor-air interface, reducing total internal reflection and enhancing light extraction while maintaining manufacturing feasibility through established nano-fabrication techniques
2Device complexity
If high refractive index semiconductor materials are used, then LED structure is simple, but external quantum efficiency is limited
Solution Approach 1:
The patent introduces three-dimensional nano-structures on the semiconductor layer surface, transforming it from a flat two-dimensional interface to a complex three-dimensional interface. This enables multiple light extraction mechanisms including scattering, refraction, and waveguide mode coupling, thereby breaking the external quantum efficiency limitation imposed by high refractive index materials while maintaining relative structural simplicity
Solution Approach 2:
The three-dimensional nano-structures act as an intermediary between the high refractive index semiconductor material and the low refractive index air environment. These nano-structures provide gradual refractive index transition and multiple extraction pathways, mediating the optical impedance mismatch and enabling efficient light extraction without changing the bulk semiconductor material properties
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 LED exhibits enhanced light extraction efficiency, with a 4.7 times improvement compared to conventional LEDs, and achieves a light extraction intensity of approximately 500 A.U. at a wavelength of 530 nm.
Implementation Method 1
a second semiconductor layer (130), wherein a surface of the second semiconductor layer (130), away from the active layer (120), comprises a number of first three-dimensional nano-structures (134)
Implementation Method 2
transforming light with large incidence angles into light with smaller angles, thereby improving the overall light extraction intensity
Data Source
AI summary
An LED comprises a first semiconductor layer, an active layer, a second semiconductor layer, a first electrode and a second electrode. The first semiconductor layer, the active layer, and the second semiconductor layer are stacked in that order and located on a surface of the first electrode. The second electrode is electrically connected with the second semiconductor layer. A number of first three-dimensional nano-structures are located on a surface of the second semiconductor layer away from the active layer. The first three-dimensional nano-structures are linear protruding structures, a cross-section of each linear protruding structure is an arc.