Organic Electroluminescent Devices with Low Refractive Index Transport Layers
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Solution Overview
Problem
Existing organic electroluminescent devices face low optical output coupling efficiency due to high refractive indices in transport layers, which hinder light emission efficiency.
Innovation Solution
Incorporating inert materials with refractive indices less than 1.5 into carrier transport layers, allowing for reduced refractive indices and improved light extraction, while maintaining high carrier transport efficiency through vacuum-doped evaporation-plating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the refractive index of the transport layer is increased to improve optical output coupling efficiency, then light extraction is improved, but carrier transport capability deteriorates
Solution Approach 1:
The transport layer is segmented into multiple sub-layers with different refractive indices. The first transport layer has a refractive index of 1.7-1.9 for optimal carrier transport, while the second transport layer has a refractive index of 1.4-1.6 to reduce total reflection and improve light extraction. This segmentation allows each sub-layer to optimize for its specific function without compromising the other.
Solution Approach 2:
Different regions of the transport layer structure are assigned different optical properties. The first transport layer positioned adjacent to the light-emitting layer maintains high refractive index for carrier transport, while the second transport layer positioned closer to the electrode uses low refractive index material to minimize optical losses. This local differentiation resolves the contradiction between carrier transport and light extraction requirements.
2Loss of energy
If the refractive index of the transport layer is decreased to reduce total reflection losses, then light extraction efficiency is improved, but carrier transport efficiency deteriorates
Solution Approach 1:
The transport function is divided between two layers: the first layer with high refractive index (1.7-1.9) ensures efficient carrier transport from the light-emitting layer, while the second layer with low refractive index (1.4-1.6) minimizes total reflection losses at the electrode interface. This segmentation allows simultaneous optimization of both carrier transport and light extraction.
Solution Approach 2:
The first transport layer acts as an intermediary between the light-emitting layer and the second transport layer. It provides the high refractive index environment needed for efficient carrier transport while transitioning to the low refractive index second layer that reduces optical losses, thereby mediating between the conflicting requirements of carrier transport and light extraction.
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
Enhances optical output coupling efficiency and light-emitting efficiency by reducing total reflection and absorption losses, while ensuring stable and uniform carrier transport.
Implementation Method 1
at least one of the carrier transport layers is doped with inert material having a refractive index less than 1.5
Implementation Method 2
manufacturing methods thereof wherein the carrier transport layers are doped with the inert material by performing vacuum-doped evaporation-plating
Data Source
AI summary
The present application discloses an organic electroluminescent device comprising carrier transport layers. The carrier transport layers include an electron transport layer and/or a hole transport layer, at least one of the carrier transport layers is doped with inert material having a refractive index less than 1.5. The present application also provides a manufacturing method of the above-mentioned organic electroluminescent device.