Aromatic Heterocycle Electron Transport Layers for TTF OLED Efficiency
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Solution Overview
Problem
Fluorescent organic electroluminescence devices (EL devices) face limitations in efficiency and require improvements to achieve higher internal quantum efficiency and lower drive voltage operation.
Innovation Solution
Incorporation of an aromatic heterocyclic derivative in the electron transporting zone, including a blocking layer, electron injecting layer, and electron transporting layer, which enhances the TTF (Triplet-Triplet Fusion) phenomenon to generate singlet excitons, thereby increasing efficiency and reducing the drive voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fluorescent organic 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 patent introduces a blocking layer as an intermediary between the emitting layer and electron transporting zone. This blocking layer mediates the interaction between triplet excitons and the electron transporting zone, enabling TTF phenomenon to occur. The blocking layer has specific properties (electron resistance, triplet energy level) that facilitate the conversion of triplet excitons to singlet excitons, thereby improving internal quantum efficiency while maintaining fluorescent device simplicity
Solution Approach 2:
The patent changes key parameters of the electron transporting zone by using compounds with wide energy gaps (greater than 2.85 eV) and high triplet energy levels. This parameter change enables the electron transporting zone to accept triplet excitons from the emitting layer and facilitate TTF phenomenon, converting non-emissive triplet excitons into emissive singlet excitons, thereby increasing internal quantum efficiency from 25% to potentially 62.5% or higher
2Productivity
If the electron transporting zone uses a compound with wide gap for increasing triplet energy, then the efficiency is improved through TTF phenomenon, but the drive voltage increases
Solution Approach 1:
The patent applies local quality by creating distinct zones with different properties: the blocking layer has high electron resistance and specific triplet energy to induce TTF, while the electron transporting zone has wide gap for high triplet energy but is optimized for electron transport. Each zone is locally optimized for its specific function, allowing the system to achieve high efficiency through TTF while managing drive voltage through proper material selection and layer design
3Productivity
If a blocking layer is designed to effectively induce TTF phenomenon with high electron resistance, then triplet excitons are converted to singlet excitons, but the device complexity increases
Solution Approach 1:
The patent segments the electron transporting function into two distinct parts: a blocking layer specifically designed to induce TTF phenomenon by converting triplet excitons to singlet excitons, and an electron transporting zone that facilitates electron injection and transport. This segmentation allows each layer to be optimized for its specific function, achieving high triplet exciton conversion efficiency while keeping the overall device structure manageable through clear functional division
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 high-efficiency emission with lower drive voltage operation by effectively inducing the TTF phenomenon, improving the performance of fluorescent organic EL devices.
Implementation Method 1
there has been disclosed a technology of extracting emissions derived from triplet excitons by a phenomenon (i.e., TTF (Triplet-Triplet Fusion) phenomenon) in which two triplet excitons collide and fuse with each other to generate singlet excitons
Implementation Method 2
An organic electroluminescence device (hereinafter, occasionally referred to as an organic EL device)
Data Source
AI summary
An organic EL device includes an anode, an emitting layer, an electron transporting zone and a cathode in this sequence, in which the electron transporting zone contains an aromatic heterocyclic derivative represented by a formula (1) below. In the formula (1), X1 to X3 are a nitrogen atom or CR1, and A is represented by a formula (2) below. In the formula (2), L1 is s single bond or a linking group, and HAr is represented by a formula (3) below. In the formula (3), Y1 is an oxygen atom, a sulfur atom or the like, and one of X11 to X18 is a carbon atom bonded to L1 by a single bond and the rest of X11 to X18 are a nitrogen atom or CR13.