Optoelectronic Device Mirror Layer Light Escape Efficiency
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Solution Overview
Problem
Optoelectronic devices with light-emitting diodes, particularly those using semiconductor microwires or nanowires, suffer from low light escape efficiency due to light being captured by the three-dimensional elements or substrate, resulting in a significant portion of emitted light not being visible.
Innovation Solution
The implementation of a substrate with a mirror layer having a high extinction coefficient and a seed layer with specific refractive and extinction coefficient properties, along with a semiconductor structure that includes wire, conical, or frustoconical semiconductor elements, to enhance light reflectivity and escape efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If light-emitting diodes are formed using three-dimensional semiconductor elements (microwires or nanowires), then the device achieves efficient light emission conversion, but a significant portion of emitted light is captured by the three-dimensional elements or substrate and does not escape
Solution Approach 1:
A mirror layer comprising a first material (chromium, rhodium, ruthenium, palladium or their alloys) with thickness between 15-50 nm is introduced as an intermediary between the substrate and the three-dimensional semiconductor elements. This mirror layer has high reflectivity (extinction coefficient ≥ 3) for wavelengths between 380-650 nm, redirecting captured light back toward the light-emitting diodes to improve escape efficiency without affecting the light emission conversion efficiency
Solution Approach 2:
The device structure combines multiple materials with complementary optical properties: the mirror layer (high extinction coefficient) works in conjunction with a seed layer (refractive index 1.5-2.5, extinction coefficient 0.5-2.0) and the III-V or II-VI semiconductor compounds. This composite structure creates optimized light management by combining reflection, refraction, and emission properties of different materials
2Loss of energy
If a mirror layer with high extinction coefficient is added to improve light reflectivity, then light escape efficiency increases, but the device structure and manufacturing complexity increase
Solution Approach 1:
The mirror layer thickness is precisely controlled within 15-50 nm to optimize reflectivity while minimizing structural complexity. This parameter optimization ensures high light escape efficiency without requiring excessively thick or complex multilayer structures, maintaining manufacturing feasibility
3Loss of energy
If the mirror layer thickness is increased to improve reflectivity, then light escape efficiency increases, but the extinction coefficient requirement becomes harder to maintain at optimal levels
Solution Approach 1:
The mirror layer thickness is optimized to 15-50 nm, which provides sufficient reflectivity while remaining manufacturable with standard thin-film deposition techniques. This thickness range balances optical performance with manufacturing precision requirements, avoiding the need for ultra-precise control of extremely thin or thick layers
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 configuration significantly increases the reflectivity of the optoelectronic device, allowing more light to escape and be visible, thereby improving the light-emitting diode's efficiency and emission characteristics.
Implementation Method 1
a first layer or first portions covering the substrate, the first layer or the first portions having a thickness greater than or equal to 15 nm and comprising a first material having an extinction coefficient greater than or equal to 3
Implementation Method 2
a second layer or second portions covering the first layer or the first portions and in contact with the first layer or the first portions, the second layer or the second portions having a thickness less than or equal to 20 nm and comprising a second material having a refractive index comprised between 1 and 3
Data Source
Figure 1~2
Figure 3~5E
Figure 6~7
AI summary
The invention concerns an optoelectronic device (40) comprising: a substrate (14); a first layer (42) covering the substrate, the first layer having a thickness greater than or equal to 15 nm and comprising a first material having an extinction coefficient greater than or equal to 3 for any wavelength between 380 and 650 nm; a second layer (18) covering and in contact with the first layer, the second layer having a thickness less than or equal to 20 nm and comprising a second material having a refraction index of between 1 and 3 and an extinction coefficient less than or equal to 1.5 or any wavelength between 380 and 650 nm; and conical or frustoconical wire semiconductor elements (24) each having a light-emitting diode stack (DEL), being in contact with the second layer.