Organic Electroluminescent Device Host Material T1 Energy Optimization
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Solution Overview
Problem
Developing an organic electroluminescent device with high efficiency, low driving voltage, and high driving durability is challenging due to the limited availability of host materials with good chemical stability, excellent carrier injection/transport properties, and a high energy level of the lowest excited triplet state (T1 energy), which are necessary to prevent luminescence quenching and ensure efficient phosphorescent material performance.
Innovation Solution
An organic electroluminescent device incorporating a compound with a specific chemical structure, represented by formulas (1), (2), and (3), which serves as a host material in the light-emitting layer, offering a high T1 energy level of 2.8 to 3.5 eV, excellent chemical stability, and superior carrier transport properties, paired with a phosphorescent material like an iridium or platinum complex, to enhance luminescence efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a host material with high T1 energy level is used to prevent luminescence quenching, then luminescence efficiency is improved, but carrier injection and transport properties deteriorate, requiring increased driving voltage
Solution Approach 1:
The patent modifies the chemical structure of the host material by introducing specific substituents (R groups) at defined positions on the aromatic ring system. This structural parameter change optimizes the balance between T1 energy level and carrier transport properties, achieving high luminescence efficiency without requiring increased driving voltage
Solution Approach 2:
The patent combines the specially designed host material with phosphorescent materials (iridium or platinum complexes) to create a composite light-emitting layer. This composite system leverages the high T1 energy of the host to prevent quenching while the phosphorescent material provides efficient luminescence, achieving both high efficiency and low driving voltage
2Loss of energy
If a host material with sufficiently high T1 energy level is used to prevent back energy transfer, then luminescence efficiency is maintained, but the selection of host materials is limited
Solution Approach 1:
The patent systematically varies substituents (R groups) at different positions (m, n) on the aromatic ring structure to create a series of host materials with different T1 energy levels and properties. This approach expands the available host material options while maintaining the required high T1 energy level to prevent back energy transfer
Solution Approach 2:
The patent introduces specific substituents at specific positions on the aromatic ring system to locally modify the electronic structure and T1 energy level. This localized modification allows precise control over host material properties to achieve the required T1 energy without compromising other essential properties
3Stability of the object's composition
If an m-phenylenediamine compound with low T1 energy level is used as host material, then chemical stability is achieved, but luminescence is quenched resulting in low luminescence efficiency
Solution Approach 1:
The patent modifies the basic m-phenylenediamine structure by adding specific substituents (R groups) and adjusting the ring system configuration. This structural parameter change increases the T1 energy level from the low value in conventional m-phenylenediamine compounds to a sufficiently high level that prevents luminescence quenching, while maintaining the inherent chemical stability of the phenylenediamine core structure
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 proposed device achieves high efficiency, low driving voltage, and improved driving durability by utilizing the compound as a host material, ensuring effective energy transfer and maintaining luminescence efficiency while reducing voltage requirements and extending device lifespan.
Implementation Method 1
the luminescence efficiency of devices has been increasing by the use of a phosphorescent material. Phosphorescent electroluminescent devices using an iridium complex or a platinum complex as a phosphorescent material
Implementation Method 2
A host material is required to have a higher T1 than a phosphorescent material because, and if not, the luminescence is quenched. When the T1 of a host material is higher than, but with only a small difference from, that of a phosphorescent material, back energy transfer from the phosphorescent material to the host material occurs partially
Implementation Method 3
With an electric field applied to the electrodes, electrons and holes are injected from the cathode and the anode, respectively, into the organic layer, where they are recombined to generate excitons, the energy of which is utilized for light emission
Data Source
AI summary
An organic electroluminescent device is provided and includes: a cathode; an anode; and a light-emitting layer between the cathode and the anode. The light-emitting layer includes a compound represented by formula (1).In formula (1), L represents a linking group; A1, A2, A3, A4, A5, A6, A7, A8, A9, and A10 each independently represent a carbon atom or a nitrogen atom, provided that at least two of A1, A5, A6, and A10 each represent a carbon atom having R′; R′ represents a substituent having a carbon atom at a bonding position thereof; a plurality of Rs each independently represent a substituent; m represents an integer; and n represents an integer of 2 to 10.