Low-Index OLED Layer Structure for Light Outcoupling
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Solution Overview
Problem
Existing light-emitting devices with low refractive index layers face challenges in carrier-transport properties and manufacturing complexity, leading to reduced outcoupling efficiency and increased power consumption.
Innovation Solution
A light-emitting device structure with a low refractive index layer positioned between the electrodes, where the layer's optical path length is optimized to enhance outcoupling efficiency and reduce manufacturing complexity, using materials with refractive indices less than 1.80 and incorporating inorganic compounds in a microcrystalline state to improve carrier transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a low refractive index layer is provided between a pair of electrodes, then outcoupling efficiency is improved, but carrier-transport property is inhibited
Solution Approach 1:
The patent changes the refractive index parameter of the layer between electrodes from conventional high values to specifically low values (less than 1.80, preferably 1.60-1.75). This parameter change enables the layer to serve dual functions: improving outcoupling efficiency by reducing total internal reflection at the electrode-interface boundary, while maintaining adequate carrier transport through careful material selection that balances optical and electrical properties.
Solution Approach 2:
The patent employs composite material structures where the low refractive index layer is integrated with the electrode structure. Specifically, a low refractive index layer is formed in direct contact with the electrode, creating a composite interface that simultaneously optimizes optical extraction and maintains electrical functionality. The composite structure allows the low refractive index material to reduce reflection losses while the electrode material continues to provide carrier injection and transport pathways.
2Productivity
If a low refractive index layer is provided outside an electrode, then outcoupling efficiency is improved, but manufacturing process becomes complicated
Solution Approach 1:
The patent merges the low refractive index layer with the existing electrode structure by forming the low refractive index layer in direct contact with the electrode surface. This integration eliminates the need for separate external low refractive index layers, reducing the number of manufacturing steps while achieving the same optical benefit. The merged structure simplifies the overall device architecture and manufacturing process.
Solution Approach 2:
The low refractive index layer positioned between the electrode and organic layer serves multiple functions simultaneously: it acts as an optical extraction enhancement layer to improve outcoupling efficiency, and it serves as part of the electrode-organic layer interface structure. This multi-functionality eliminates the need for separate dedicated layers for each function, thereby simplifying the manufacturing process.
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 solution achieves high outcoupling efficiency, reduced power consumption, and simplified manufacturing while maintaining high emission efficiency and reliability.
Implementation Method 1
attenuation due to reflection caused by a difference in refractive index is a significant factor in decreasing the efficiency of the device; thus, in order to reduce the influence, a structure in which a layer composed of a low refractive index material is formed in an EL layer has been proposed
Implementation Method 2
Light-emitting devices (organic EL devices) that use organic compounds and utilize electroluminescence (EL)
Data Source
AI summary
A light-emitting device with high outcoupling efficiency is provided.In the light-emitting device including a light-emitting layer between a pair of electrodes, a low refractive index layer containing an organic compound and an inorganic compound is provided between the light-emitting layer and an anode or between the light-emitting layer and a cathode, and the low refractive index layer has a refractive index of less than or equal to 1.80 at a wavelength of light extracted from the light-emitting layer.