LED Display Isolation Layer Refractive Index Bridge
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Solution Overview
Problem
The light extraction efficiency of LED display devices is limited by total internal reflection due to the refractive index mismatch between the micro light emitting device and the surrounding medium, such as air or encapsulation layers.
Innovation Solution
The LED display incorporates a first isolation layer with a refractive index less than or equal to the micro light emitting device, and an encapsulation layer with a refractive index greater than or equal to the isolation layer, reducing total internal reflection and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional LED structure with direct contact between the light emitting device and encapsulation layer is used, then the device structure is simple, but the light extraction efficiency is limited due to total internal reflection
Solution Approach 1:
An isolation layer with refractive index n1 is introduced between the micro light emitting device (refractive index ndevice) and the encapsulation layer (refractive index n2), where n2 < n1 < ndevice. This intermediary layer acts as a refractive index bridge, reducing the abrupt refractive index mismatch at the interface and minimizing total internal reflection, thereby improving light extraction efficiency without significantly complicating the manufacturing process
Solution Approach 2:
The patent changes the refractive index parameter by introducing an isolation layer with a specific refractive index value that is lower than the micro light emitting device but higher than the encapsulation layer. This parameter optimization creates a gradual refractive index transition, reducing optical impedance mismatch and enhancing light extraction efficiency
2Loss of energy
If the refractive index of the encapsulation layer is increased to match the micro light emitting device, then light extraction efficiency improves, but the refractive index mismatch with air increases causing more total internal reflection at the outer interface
Solution Approach 1:
The isolation layer serves as a dual-interface intermediary: at the inner interface with the micro light emitting device, it reduces reflection by having a lower refractive index than the device; at the outer interface with the encapsulation layer, it provides a gradual transition that minimizes total internal reflection. This mediator approach optimizes light extraction at both interfaces simultaneously
Solution Approach 2:
By optimizing the refractive index parameter of the isolation layer to fall between that of the micro light emitting device and the encapsulation layer, the patent creates an ideal gradient structure that minimizes optical reflection losses at both interfaces, effectively solving the contradictory requirements of light extraction efficiency and reduced total internal reflection
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 effectively increases the light extraction efficiency of the micro light emitting device by minimizing internal reflections, leading to improved luminance intensity and color fidelity in LED displays.
Implementation Method 1
the light extraction efficiency of a LED in a display device may still be limited by the outside medium (either air or an encapsulation layer) due to total internal reflection
Implementation Method 2
the first isolation layer has a refractive index n1, the micro light emitting device has a refractive index ndevice, and ndevice≧n1
Data Source
AI summary
A light-emitting device display includes a substrate, a first bottom electrode, a second bottom electrode, a micro light emitting device, a first isolation layer, an opposite electrode, and an encapsulation layer. The first and second bottom electrodes are disposed on the substrate. The micro light emitting device is disposed on the first bottom electrode and electrically connected to the first bottom electrode. The first isolation layer at least partially covers a side surface of the micro light emitting device, in which the first isolation layer has a refractive index n1, and the micro light emitting device has a refractive index ndevice, and ndevice≧n1. The opposite electrode is disposed on the micro light emitting device and electrically connected to the micro light emitting device and the second bottom electrode. The encapsulation layer at least covers the micro light emitting device and the first isolation layer.