Aromatic Heterocyclic Derivative Triplet-Triplet Fusion
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Solution Overview
Problem
Current organic electroluminescence devices have limited efficiency due to the theoretical internal quantum efficiency of 25% in fluorescent devices, as they primarily utilize singlet excitons for emission, while triplet excitons are not effectively utilized, leading to inefficiencies in energy conversion and emission.
Innovation Solution
The development of an aromatic heterocyclic derivative for use in an organic electroluminescence device, specifically in a blocking layer and electron transporting zone, which facilitates the Triplet-Triplet Fusion (TTF) phenomenon by managing triplet energy levels and exciton transfer between host and dopant materials, enhancing the generation of singlet excitons and improving luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fluorescent EL device uses emission caused by singlet excitons, then the device can be manufactured with simpler materials and processes, but the internal quantum efficiency is limited to 25%
Solution Approach 1:
The invention converts the previously harmful or wasted triplet excitons (which constituted 75% of generated excitons but did not contribute to emission) into useful singlet excitons through the TTF phenomenon. By introducing a blocking layer with specific properties (wide gap, high triplet energy) adjacent to the emitting layer, triplet excitons are accumulated and induced to undergo fusion, generating additional singlet excitons that contribute to fluorescence emission. This transforms the waste energy into beneficial emission, enabling internal quantum efficiency to exceed the conventional 25% limit while maintaining fluorescent device simplicity.
Solution Approach 2:
The invention changes the energy level parameters of the blocking layer materials to achieve the desired TTF effect. Specifically, the blocking layer is designed with a wide energy gap (2.85-3.20 eV) and high triplet energy (2.50-2.85 eV), which are critical parameters for effectively accumulating triplet excitons and inducing their fusion. By carefully selecting and optimizing these material parameters, the device achieves enhanced efficiency without sacrificing the ease of manufacture associated with fluorescent devices.
2Productivity
If a blocking layer is designed with a wide gap to increase triplet energy for effective TTF phenomenon, then the internal quantum efficiency is improved, but the device requires more complex material selection and layer design
Solution Approach 1:
The blocking layer serves as an intermediary component between the emitting layer and the electron transporting zone. It mediates the interaction between triplet excitons generated in the emitting layer and the host/dopant materials, providing a controlled environment for TTF phenomenon to occur. The blocking layer's specific energy level structure acts as a bridge, allowing triplet excitons to be accumulated and fused while preventing their loss to other processes. This intermediary structure simplifies the overall design by localizing the complex TTF mechanism to a specific layer with defined properties, rather than requiring complex modifications throughout the entire device structure.
3Productivity
If triplet excitons are utilized through TTF phenomenon to generate singlet excitons, then the luminous efficiency is enhanced, but the device requires specific material properties and layer configurations
Solution Approach 1:
The invention applies local quality by endowing the blocking layer with specific, localized properties (wide gap, high triplet energy) that are different from other layers in the device. Rather than requiring all materials throughout the device to have specialized properties for TTF, the complex functionality is concentrated in the blocking layer adjacent to the emitting layer. This localized approach allows the rest of the device to maintain standard fluorescent device materials and structures, preserving adaptability and ease of manufacture while achieving enhanced luminous efficiency through the specialized blocking layer.
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 aromatic heterocyclic derivative enables a significant increase in internal quantum efficiency by efficiently converting triplet excitons into singlet excitons through the TTF phenomenon, leading to enhanced luminous efficiency and reduced operational voltage in organic electroluminescence devices.
Implementation Method 1
a technology of obtaining emission derived from triplet excitons by a phenomenon in which singlet excitons are generated by collision and fusion of two triplet excitons, (i.e., a TTF (Triplet-Triplet Fusion) phenomenon)
Implementation Method 2
When a voltage is applied to the organic EL device, holes are injected from an anode and electrons are injected from a cathode. The holes and the electrons are recombined in an emitting layer to form excitons.
Implementation Method 3
managing triplet energy levels and exciton transfer between host and dopant materials
Data Source
AI summary
An aromatic heterocyclic derivative is represented by a formula (1) below.In the formula (1), X1 to X3 each are a nitrogen atom or CR1, with a proviso that at least one of X1 to X3 is a nitrogen atom. A is represented by a formula (2) and B is represented by a formula (4) below.