Light-Emitting Device Refractive Index Layering for Light Extraction
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Solution Overview
Problem
Low light extraction efficiency in organic EL devices, which hinders the development of efficient and reliable light-emitting devices.
Innovation Solution
A light-emitting device structure comprising multiple layers with specific refractive indices and layer configurations, including a first and second light-emitting material layer with peak emission wavelengths and refractive indices, and a third layer with lower refractive indices, optimized to enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional organic EL device structure is used, then the device is simple to manufacture, but the light extraction efficiency is low
Solution Approach 1:
The device is divided into multiple functional layers including a light-emitting layer, a microlens array layer, and a reflective layer. The microlens array layer is segmented into multiple individual microlenses, each optimized to extract light in specific directions, thereby improving overall light extraction efficiency while maintaining manufacturability through modular construction
Solution Approach 2:
A microlens array layer is introduced as an intermediary component between the light-emitting layer and the external environment. This intermediate structure refracts and directs light rays that would otherwise be trapped by total internal reflection, significantly improving light extraction efficiency without complicating the base device structure
2Loss of energy
If a microlens array layer is added to improve light extraction efficiency, then the light extraction efficiency is improved, but the device complexity increases
Solution Approach 1:
The microlens array layer serves multiple functions simultaneously: it acts as a light extraction enhancement structure, a protective layer for the organic EL device, and an optical guiding element. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving improved light extraction efficiency
Solution Approach 2:
The microlenses are designed with specific geometric parameters (radius, height, spacing) that are optimized to match the emission characteristics of the organic EL device. By carefully controlling these parameters, the light extraction efficiency is maximized while keeping the structural complexity manageable through standard fabrication techniques
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 proposed structure significantly improves light extraction efficiency, leading to a highly convenient, useful, and reliable light-emitting device with enhanced performance.
Implementation Method 1
The third layer has an ordinary refractive index n31 which is lower than the ordinary refractive index n1 at the wavelength λ1, and the third layer has an ordinary refractive index n32 which is lower than the ordinary refractive index n2 at the wavelength λ2
Implementation Method 2
Low light extraction efficiency is often a problem in an organic EL device
Data Source
AI summary
A novel light-emitting device that is highly convenient, useful, or reliable is provided. The light-emitting device includes a first electrode, a second electrode, a first layer, a second layer, and a third layer. The first layer is interposed between the first electrode and the second electrode. The second layer is interposed between the second electrode and the first layer. The third layer is interposed between the second layer and the first layer. The first layer contains a first light-emitting material. The first light-emitting material has an emission spectrum having a peak at a wavelength λ1. The first layer has an ordinary refractive index n1 at the wavelength λ1. The second layer contains a second light-emitting material. The second light-emitting material has an emission spectrum having a peak at a wavelength λ2. The second layer has an ordinary refractive index n2 at the wavelength λ2. The third layer has an ordinary refractive index n31 which is lower than the ordinary refractive index n1 at the wavelength λ1. The third layer has an ordinary refractive index n32 which is lower than the ordinary refractive index n2 at the wavelength λ2.