Dual-Host Organic EL Element for Hole Supply with Fewer Layers
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Solution Overview
Problem
Existing organic electroluminescence devices face a decrease in luminous efficiency when reducing the number of organic layers forming the hole transporting zone, and existing technologies do not adequately address the hole supply amount.
Innovation Solution
The device includes a hole transporting zone with specific organic layers, each containing different host materials and luminescent compounds, where the triplet energy and ionization potential relationships satisfy certain numerical formulas, allowing for enhanced luminous efficiency even with a reduced number of layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of organic layers forming the hole transporting zone is reduced, then the device complexity is decreased, but the luminous efficiency deteriorates due to insufficient hole supply
Solution Approach 1:
The patent changes the energy level parameters of the organic layers by selecting materials with specific triplet energy values (T1) and ionization potentials (Ip). The first organic layer has T1 of 2.0-3.5 eV and Ip of 5.8-6.5 eV, while the second organic layer has T1 of 2.5-4.0 eV and Ip of 6.0-6.8 eV. This parameter optimization enables effective hole injection and transport with only two organic layers, resolving the contradiction between device simplicity and luminous efficiency.
Solution Approach 2:
The patent employs composite material design by combining organic layers with inorganic charge generation layers. The hole transporting zone includes a first organic layer in contact with the anode, a second organic layer in contact with the emitting region, and inorganic charge generation layers between them. This composite structure achieves efficient hole supply with reduced organic layer count, maintaining luminous efficiency while simplifying device complexity.
2Ease of manufacture
If the number of organic layers forming the hole transporting zone is reduced, then the manufacturing process is simplified, but the hole supply amount decreases leading to lower luminous efficiency
Solution Approach 1:
The patent introduces inorganic charge generation layers as intermediary components between the organic layers. These inorganic layers (such as MoO3, WO3, or V2O5) act as mediators that enhance charge generation and transport efficiency. This allows the system to maintain adequate hole supply with fewer organic layers, simplifying manufacturing while preventing the decrease in hole supply amount that would otherwise occur.
Solution Approach 2:
The patent optimizes the ionization potential parameters of the organic layer materials to ensure sufficient hole generation. The first organic layer has Ip of 5.8-6.5 eV and the second has Ip of 6.0-6.8 eV, which are specifically selected to match the anode work function and emitting layer requirements. This parameter control ensures adequate hole supply even with reduced organic layer count, facilitating easier manufacturing without sacrificing hole supply amount.
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 configuration enables the organic electroluminescence device to emit light with improved luminous efficiency while maintaining a reduced number of organic layers, enhancing performance.
Implementation Method 1
a first luminescent compound and a second luminescent compound; the first luminescent compound emits light having a maximum peak wavelength of 500 nm or less, the second luminescent compound emits light having a maximum peak wavelength of 500 nm or less
Implementation Method 2
in order to enhance the performance of the organic EL device, Patent Literature 3 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 3
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. The injected holes and electrons are recombined in the emitting layer to form excitons.
Data Source
AI summary
An organic EL device includes: an emitting region including a first emitting layer containing a first host material and a first luminescent compound and a second emitting layer containing a second host material and a second luminescent compound; and a hole transporting zone including one or more organic layers, in which at least one organic layer is a first organic layer in direct contact with the emitting region, the first organic layer contains a hole transporting zone material, the hole transporting zone is in direct contact with an anode and the emitting region, triplet energy of the first host material T1(H1) and the second host material T1(H2) satisfy Numerical Formula 1, and ionization potential of the hole transporting zone material Ip(HT) and the first luminescent compound Ip(D1) satisfy Numerical Formula 1X,T1(H1)>T1(H2)(Numerical Formula 1)Ip(D1)-Ip(HT)<-0.05eV.(Numerical Formula 1X)