Organic EL Emitting Layer Energy Alignment for Efficiency and Lifetime
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Solution Overview
Problem
Existing organic electroluminescence devices face challenges in maintaining luminous efficiency and lifetime performance.
Innovation Solution
The device incorporates specific energy level and triplet energy relationships between host materials in emitting layers, along with the use of compounds with defined molecular structures, to enhance efficiency and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional emitting layers are used in organic EL devices, then the device can operate, but luminous efficiency deteriorates and lifetime is shortened
Solution Approach 1:
The patent applies parameter changes by precisely controlling the energy levels of host materials. Specifically, it sets the triplet energy T1(H1) of the first host material to 2.5-3.2 eV and T1(H2) of the second host material to 2.3-3.0 eV, with a energy difference of 0.1-0.7 eV. This optimized energy parameter configuration enables efficient triplet exciton management through TTF while preventing degradation, thereby simultaneously improving luminous efficiency and extending device lifetime.
Solution Approach 2:
The patent employs composite materials by combining two different host materials (first host material and second host material) in the emitting layer. This composite structure allows the first host material to generate triplet excitons at optimal energy levels while the second host material facilitates triplet-triplet fusion, creating a synergistic effect that enhances both efficiency and stability without compromising device lifetime.
2Loss of energy
If multiple emitting layers are layered to enhance performance, then luminous efficiency improves, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the emitting layer into two distinct functional zones: a first emitting layer region containing the first host material for triplet exciton generation, and a second emitting layer region containing the second host material for triplet-triplet fusion. This segmented approach enables independent optimization of each region's energy parameters while maintaining overall device simplicity and avoiding the complexity of multiple stacked emitting layers.
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 maintains luminous efficiency and extends the device's lifetime by optimizing the energy levels and triplet energies of host materials in the emitting layers.
Implementation Method 1
Patent Literature 2 describes a phenomenon in which a singlet exciton is generated by collision and fusion of two triplet excitons (hereinafter, occasionally referred to as a Triplet-Triplet Fusion (TTF) phenomenon)
Implementation Method 2
An organic electroluminescence device has found its application in a full-color display for mobile phones, televisions, and the like. When voltage is applied to an organic EL device, holes are injected from an anode and electrons are injected from a cathode into an emitting layer.
Data Source
AI summary
An organic EL device includes an emitting region and a first anode side organic layer. The first anode side organic layer contains a first material. The emitting region includes a first emitting layer containing first and second host materials and a second emitting layer containing a third host material. Energy levels of highest occupied molecular orbitals of the first material, the first host material, and the second host material HOMO(HT1), HOMO(H1), and HOMO(H2) satisfy a relationship of a numerical formula (Numerical Formula A1) below, and triplet energies of the first host material, the second host material, and the third host material T1(H1), T1(H2), and T1(H3) satisfy relationships of numerical formulae (Numerical Formula A2 and Numerical Formula A3) below,HOMO(HT1)>HOMO(H2)>HOMO(H1)(Numerical Formula A1)T1(H1)>T1(H3)(Numerical Formula A2)T1(H2)>T1(H3).(Numerical Formula A3)