Organic Light-Emitting Device Host-Dopant LUMO Alignment
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Solution Overview
Problem
Organic light-emitting devices using delayed fluorescent dopants are vulnerable to electrons, leading to reduced lifespan due to weak bonding strength, which affects the efficiency and stability of the device.
Innovation Solution
An organic light-emitting device is designed with a light-emitting layer comprising a delayed fluorescent dopant and a host compound where the LUMO energy level difference is ≤0.2 eV, and the host has stronger binding energy in an anion state than the dopant, directing electron flow to the host and enhancing the device's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a donor-acceptor structure with large angle between donor and acceptor is used to minimize singlet-triplet energy gap, then delayed fluorescence efficiency is improved, but bonding strength is weakened and electron vulnerability increases
Solution Approach 1:
The patent modifies the molecular structure parameters of the dopant by introducing a six-membered aromatic ring containing nitrogen at the acceptor position and adjusting the spatial arrangement to achieve an angle of 120° or more between donor and acceptor. This parameter optimization simultaneously achieves high delayed fluorescence efficiency and enhanced bonding strength, resolving the contradiction between productivity and strength.
2Reliability
If LUMO energy level difference between host and dopant is minimized (≤0.2 eV), then electron flow toward host is enhanced and dopant lifespan is improved, but energy gap between singlet and triplet must be maintained small for delayed fluorescence
Solution Approach 1:
The patent optimizes the energy level parameters by selecting host materials with LUMO levels within 0.2 eV of the dopant's LUMO level, while simultaneously designing the dopant's molecular structure to maintain a small singlet-triplet energy gap. This dual parameter optimization enables both extended dopant lifespan through reduced electron attack and preserved delayed fluorescence efficiency.
Solution Approach 2:
The host material acts as an intermediary that protects the dopant from direct electron attack while allowing energy transfer. By positioning the host's LUMO level slightly lower than the dopant's, electrons are directed to the host which has stronger bonding strength, thereby protecting the dopant while maintaining the necessary energy gap for delayed fluorescence.
3Reliability
If binding energy of dopant in anion state is reduced, then electron vulnerability is decreased and lifespan is extended, but device efficiency may be affected
Solution Approach 1:
The patent changes the binding energy parameter by introducing nitrogen-containing six-membered aromatic ring structures at the acceptor position, which inherently possess higher bonding strength in anion states. This structural modification reduces electron vulnerability and extends device lifespan while maintaining efficient energy transfer through optimized LUMO level alignment.
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 significantly improves the lifespan of the device by protecting the dopant from electron attack, resulting in a longer operational life and improved efficiency.
Implementation Method 1
controls the LUMO energy level of a host and a delayed fluorescent dopant constituting a light-emitting layer so that electrons flow toward the host
Implementation Method 2
molecules are designed to reduce the singlet-triplet energy gap, inducing reverse intersystem crossing (RISC) converting a triplet to a singlet using only thermal energy at room temperature
Implementation Method 3
Organic luminescence refers to a phenomenon in which electrical energy is converted into light energy using organic materials
Data Source
AI summary
The present specification relates to: a delayed fluorescence organic light-emitting device that comprises a light-emitting layer comprising a first compound which has a LUMO energy level of EL1 and which is a delayed fluorescence dopant, and a second compound which has a LUMO energy level of EL2 and which is a host, and that satisfies |EL1|−|EL2|≤0.2 eV, the binding energy of the first compound in an anion state being lower than the binding energy of the second compound in an anion state; and a delayed fluorescence sensitized hyperfluorescence device further comprising a third compound, which is a delayed fluorescence or fluorescent compound. A host, which has excellent electron transport capacity to have a LUMO energy level similar to that of a delayed fluorescence dopant, is used to delay the deterioration of a delayed fluorescent compound, and thus the lifespan of a delayed fluorescence organic light-emitting device or a hyperfluorescence organic light-emitting device can be remarkably improved.