LED Encapsulation Layout for Higher Light Extraction in Dense Arrays
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Solution Overview
Problem
Existing optoelectronic devices with light-emitting diodes, such as microwires or nanowires, suffer from low light extraction efficiency due to a significant portion of photons not escaping and being absorbed or trapped by neighboring diodes.
Innovation Solution
The implementation of an optoelectronic device design featuring semiconductor light-emitting diodes with encapsulation blocks that are partially transparent to radiation, an electrically conductive layer, and optional conformal dielectric and photoluminescent layers, along with lenses and angular filters, to enhance light extraction efficiency by optimizing the refractive indices and structural arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If light-emitting diodes are arranged closely together to increase device density, then productivity and device compactness are improved, but light extraction efficiency deteriorates due to photons being absorbed or trapped by neighboring diodes
Solution Approach 1:
An encapsulation layer with intermediate refractive index (1.3-1.6) is introduced between adjacent light-emitting diodes. This encapsulation layer acts as an optical intermediary that reduces total internal reflection at the semiconductor-air interface and prevents photons from being absorbed by neighboring diodes, thereby maintaining high light extraction efficiency while enabling close spacing of diodes for increased device density
Solution Approach 2:
The refractive index of the encapsulation layer is specifically optimized to be between 1.3 and 1.6, which is higher than air (1.0) but lower than typical semiconductor materials (2.0-3.0). This parameter change creates optimal optical conditions for light extraction by reducing the refractive index contrast at interfaces, thereby minimizing total internal reflection and improving photon escape probability while allowing closely spaced diode arrangements
2Loss of energy
If a high refractive index encapsulation material is used to improve light extraction, then light extraction efficiency is improved, but manufacturing precision requirements increase due to stricter control needs on layer thickness and uniformity
Solution Approach 1:
Instead of using high refractive index materials that would require extremely precise thickness control, the invention selects encapsulation materials with refractive indices between 1.3 and 1.6. This parameter selection provides a favorable balance: the refractive index is sufficiently different from air to improve light extraction through reduced total internal reflection, yet the absolute thickness requirements are more relaxed compared to high-index material systems, thereby reducing manufacturing precision requirements while still achieving high light extraction efficiency
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 design significantly increases the light extraction efficiency by improving the escape of photons from the device, reducing absorption, and enhancing the directivity of emitted light, leading to improved performance and efficiency in optoelectronic devices.
Implementation Method 1
the refractive index of the encapsulation block covering at least one of the light-emitting diodes or one of the groups of light-emitting diodes is between 1.3 and 1.6
Implementation Method 2
a fraction of the photons emitted within each LED do not escape from the LED
Implementation Method 3
the device further comprises, for at least one light-emitting diode, a photoluminescent layer covering the encapsulation block
Implementation Method 4
the device comprises lenses covering the encapsulation blocks
Implementation Method 5
the device further comprises an angular filter covering the lenses
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
The present description relates to an optoelectronic device (5) comprising a carrier (10) comprising a face (12); light-emitting diodes (DEL) resting on the face and comprising semiconductor elements (16) that are rod-like, conical or frustoconical; for each light-emitting diode, an encapsulating block (25) that is at least partially transparent to the radiation emitted by the light-emitting diodes and that covers the light-emitting diode, the maximum thickness of the encapsulating block being comprised between 1 pm and 30 pm, air gaps (37) being present between the encapsulating blocks covering adjacent diodes; and an electrically conductive layer (30) covering the encapsulating blocks, wherein the refractive index of the encapsulating block covering at least one of the light-emitting diodes is comprised between 1.3 and 1.6.