Organic EL Electron Transport Layer Composition for Efficiency
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Solution Overview
Problem
Conventional organic electroluminescence devices face a trade-off between luminous efficiency and device lifetime, where increasing one parameter typically results in a decrease in the other, making it difficult to enhance both simultaneously.
Innovation Solution
Incorporating a first compound with low electron mobility (1.0×10−5 cm2/Vs or lower) in the electron-transporting zone, along with specific compounds represented by formulas (11), (12), and (13), to prevent carrier accumulation at the emitting layer interface, thereby suppressing interactions between carriers and excitons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional materials and structures are used in the electron-transporting zone, then the device structure is simple, but carrier accumulation occurs at the emitting layer interface, causing trade-off between luminous efficiency and device lifetime
Solution Approach 1:
The electron-transporting zone is divided into multiple layers: a first layer containing a first compound and a second compound (formulas 11-13), and a second layer containing a third compound. This segmentation allows each layer to have optimized electron mobility characteristics, preventing carrier accumulation at the emitting layer interface while maintaining overall device performance.
Solution Approach 2:
The patent specifies precise electron mobility parameters for compounds in different layers. The first compound has electron mobility of 1.0×10⁻⁶ to 1.0×10⁻⁸ cm²/Vs, the second compound (formulas 11-13) has 1.0×10⁻⁵ to 1.0×10⁻⁷ cm²/Vs, and the third compound has 1.0×10⁻⁶ to 1.0×10⁻⁸ cm²/Vs. These parameter changes optimize carrier transport and prevent accumulation, resolving the trade-off between luminous efficiency and device lifetime.
2Productivity
If electron mobility is increased to improve carrier transport, then carrier accumulation at the emitting layer interface increases, but luminous efficiency decreases due to carrier-exciton interactions
Solution Approach 1:
Different regions of the electron-transporting zone are assigned different electron mobility characteristics. The first layer (with first and second compounds) has lower electron mobility to prevent carrier accumulation, while the second layer (with third compound) has higher electron mobility for efficient carrier transport. This local quality differentiation resolves the contradiction between carrier transport efficiency and luminous efficiency.
Solution Approach 2:
The first layer acts as an intermediary between the emitting layer and the second electron-transporting layer. By using compounds with specific low electron mobility (1.0×10⁻⁶ to 1.0×10⁻⁸ cm²/Vs) in this intermediate zone, carriers are prevented from accumulating at the emitting layer interface, thereby reducing carrier-exciton interactions and energy loss while still allowing efficient overall carrier transport through the device.
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 approach allows for an increase in either luminous efficiency or device lifetime without compromising the other, effectively pushing the performance limits of organic electroluminescence devices beyond conventional trade-off constraints.
Implementation Method 1
the first compound has an electron mobility μ1 of the first compound of 1.0×10−5 cm2/Vs or lower
Data Source
AI summary
An organic electroluminescence device having a cathode; an anode; and an emitting layer disposed between the cathode, wherein a first layer in an electron-transporting zone disposed between the emitting layer and the cathode contains a first compound and a second compound, the electron mobility μ1 of the first compound is 1.0×10−5 cm2/Vs or lower, and the second compound is one or more selected from the group consisting of compounds represented by each of the following formulas (11), (12), and (13), provided that the first compound and the second compound are different compounds.