Organic Electroluminescent Element with Segmented Emission Layers
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Solution Overview
Problem
Organic electroluminescent elements face challenges in achieving stable white light emission with high efficiency and prolonged life due to chromaticity shifts caused by variations in layer quality and carrier injection balance, especially when using multiple emission layers with different peak wavelengths.
Innovation Solution
An organic electroluminescent element is designed with a two-layer structure, where one emission layer contains a host compound and two types of emission dopants, including a phosphorescence-emitting material, and the other layer contains a host compound and one type of dopant, with a non-emitting intermediate layer to control carrier injection and reduce chromaticity shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multiple emission layers with different peak wavelengths are used to achieve white light emission, then emission efficiency is improved, but chromaticity shifts occur due to variations in layer quality and carrier injection balance
Solution Approach 1:
The emission layer is divided into two distinct layers: a first emission layer containing a fluorescent dopant and a second emission layer containing a phosphorescent dopant. This segmentation allows each layer to be optimized independently for its specific emission mechanism, improving overall emission efficiency while maintaining chromaticity stability through controlled carrier injection in each layer
Solution Approach 2:
A non-emitting intermediate layer is introduced between the first and second emission layers. This intermediary layer acts as a buffer that stabilizes carrier injection and prevents direct interaction between the fluorescent and phosphorescent dopants, thereby preventing chromaticity shifts while maintaining high emission efficiency
2Device complexity
If a single emission layer with multiple dopants is used, then device complexity is reduced, but chromaticity shifts occur due to carrier injection balance variations
Solution Approach 1:
Instead of using a single emission layer with multiple dopants, the invention segments the emission function into two separate layers. The first layer contains the fluorescent dopant and the second layer contains the phosphorescent dopant, eliminating carrier injection balance variations that cause chromaticity shifts while maintaining relatively simple device structure
Solution Approach 2:
A non-emitting intermediate layer is positioned between the first and second emission layers to stabilize carrier injection. This intermediary prevents direct competition between fluorescent and phosphorescent dopants for carriers, thereby stabilizing chromaticity while keeping the overall device structure simple and manageable
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 inhibits chromaticity shifts, enhances emission efficiency, and prolongs the life of the organic electroluminescent element by stabilizing carrier injection and interlayer adhesion, while allowing for easy production and efficient white light emission.
Implementation Method 1
an organic electroluminescent element is an element provided with a constitution comprising an emission layer containing a emitting substance being sandwiched with a cathode and an anode, and an exciton is generated by an electron and a positive hole being injected into the emission layer to be recombined, resulting emission utilizing light release (fluorescence phosphorescence) at the time of deactivation of said exciton
Data Source
AI summary
An organic electroluminescent element containing organic layers sandwiched between an anode and a cathode, wherein the organic layers incorporate an emission layer A containing a host compound A and at least two types of emission dopants, and an emission layer B containing a host compound B and at least one type of emission dopant, provided that at least one of the emission dopants contained in the emission layer A is a phosphorescence-emitting material.