Organic EL Intermediate Layer Material for Balanced White Emission
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Solution Overview
Problem
Existing organic electroluminescence (EL) devices face challenges in achieving balanced white emission due to excessive electron blocking by materials like α-NPD, leading to shortened device life and poor mass productivity, and using electron-transporting materials results in low luminous efficiency and emission balance sensitivity to thin film thickness.
Innovation Solution
Incorporating a specific aromatic amine derivative with dibenzofuran or dibenzothiophene structure in the intermediate layer between emitting layers, which balances charge transport and blocks electrons effectively, allowing for well-balanced emission and increased thickness tolerance, thereby enhancing luminous efficiency and device longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If α-NPD is used in the intermediate layer to block electrons, then emission balance is improved, but device life is shortened due to electron accumulation and emitting layer deterioration
Solution Approach 1:
The patent changes the material parameters of the intermediate layer by using compounds with specific LUMO levels (higher than α-NPD) and appropriate HOMO levels. This parameter change allows the intermediate layer to block electrons effectively while preventing electron accumulation, thus maintaining emission balance without shortening device life.
Solution Approach 2:
The patent employs composite material design by combining hole-transporting capability with appropriate electron-blocking properties in the intermediate layer material. The selected compounds (e.g., mCP, TCTA, TAPC) provide a composite functional profile that balances hole transport and electron blocking without causing harmful electron accumulation.
2Reliability
If α-NPD is used in the intermediate layer, then electron blocking is enhanced, but mass productivity is reduced due to extremely difficult film thickness control
Solution Approach 1:
The patent changes the material selection parameters by choosing compounds with LUMO levels significantly higher than the emitting layers, which provides robust electron blocking capability. This allows the intermediate layer thickness to be increased to several nanometers, making film thickness control feasible for mass production while maintaining effective electron blocking.
3Productivity
If intermediate layer thickness is increased to improve mass productivity, then emission balance becomes sensitive to thickness changes, but this sensitivity reduces productivity
Solution Approach 1:
The patent changes the material parameters by selecting compounds with appropriately high LUMO levels and suitable HOMO levels. This parameter optimization creates a wide tolerance window for film thickness, reducing sensitivity to thickness variations and enabling mass production with standard manufacturing precision.
4Speed
If electron-transporting material is used in the intermediate layer, then electron transport is improved, but hole transport capability is poor, reducing luminous efficiency
Solution Approach 1:
The patent applies local quality principle by designing the intermediate layer with specific material properties: high LUMO level for electron blocking, appropriate HOMO level for hole transport, and sufficient thickness for stable film formation. This localized optimization of material properties enables the intermediate layer to perform hole transport while blocking electrons, maintaining high luminous efficiency.
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 enables high luminous efficiency and extended life of organic EL devices with improved mass productivity by ensuring balanced charge transport and emission across emitting layers, while allowing for thicker intermediate layers and reduced sensitivity to film thickness variations.
Implementation Method 1
Due to the formation of the intermediate layer, each emitting layer is caused to emit light in a well-balanced manner. Since α-NPD is a hole-transporting material, when α-NPD is used in the intermediate layer, while highly efficient emission can be obtained by blocking electrons
Implementation Method 2
Since α-NPD is a hole-transporting material, when α-NPD is used in the intermediate layer, while highly efficient emission can be obtained by blocking electrons
Implementation Method 3
An organic electroluminescence device that emits light utilizing an organic electroluminescence (EL) phenomenon
Data Source
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AI summary
An organic electroluminescence device that includes, between an anode 41 and a cathode 42, an organic layer stacked structure 43 that comprises stacked plural emitting layers that emit light of different colors, wherein the organic electroluminescent device comprises, between the emitting layers, at least one intermediate layer that comprises a compound represented by the following formula (1) in which at least one of Ar1, Ar2 and Ar3 is a group represented by the following formula (2):