Organic EL Emitter Energy Level Design for Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current organic electroluminescence devices have limitations in internal quantum efficiency due to the reliance on singlet excitons, with efforts to improve performance focusing on utilizing triplet excitons through thermally activated delayed fluorescence mechanisms, but there is a need for enhanced longevity and efficiency.
Innovation Solution
An organic electroluminescence device incorporating a specific combination of a first compound and a second compound in the emitting layer, where the singlet energy of the second compound is higher than that of the first compound, facilitating improved exciton generation and reduced recombination, thereby extending device lifetime and enhancing luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fluorescent organic EL device uses only singlet excitons for light emission, then the device structure is simple, but the internal quantum efficiency is limited to 25%
Solution Approach 1:
The patent changes the energy level parameters of the compounds used in the emitting layer. Specifically, it selects a first compound with a triplet energy level (ET) of 2.0 eV or more and a second compound with a singlet energy level (S1) of 2.3 eV or more, where S1 > ET. This parameter configuration enables efficient triplet exciton utilization through thermal activation while maintaining device simplicity.
Solution Approach 2:
The patent employs a composite emitting layer containing two different organic compounds with specifically designed energy level relationships. The first compound (with high triplet energy) and second compound (with higher singlet energy) work synergistically to achieve both simple device structure and high internal quantum efficiency exceeding 25% through delayed fluorescence mechanism.
2Productivity
If triplet excitons are utilized through thermally activated delayed fluorescence, then internal quantum efficiency improves, but device lifetime is reduced
Solution Approach 1:
The patent optimizes the energy level parameters by selecting compounds where the singlet energy (S1) is significantly higher than triplet energy (ET), with S1 ≥ 2.3 eV and ET ≥ 2.0 eV. This energy gap configuration reduces non-radiative decay and thermal degradation, thereby extending device lifetime while maintaining high internal quantum efficiency through delayed fluorescence.
Solution Approach 2:
The patent assigns specific functional roles to different compounds in the emitting layer based on their local energy level characteristics. The first compound provides high triplet energy to prevent exciton loss, while the second compound provides high singlet energy to enable efficient delayed fluorescence emission. This localized functional differentiation improves both efficiency and stability.
3Productivity
If the singlet energy of the second compound is set higher than that of the first compound, then exciton generation probability in the second compound increases, but the energy level configuration becomes more restrictive
Solution Approach 1:
The patent establishes clear numerical thresholds for energy level parameters: triplet energy ET ≥ 2.0 eV for the first compound and singlet energy S1 ≥ 2.3 eV for the second compound, with the constraint S1 > ET. This standardized parameter specification simplifies material selection and device design while ensuring high exciton generation probability in the second compound.
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 configuration enhances the probability of exciton generation in the second compound, inhibiting deterioration of the first compound and improving luminous efficiency, resulting in a longer-lasting and more efficient organic electroluminescence device.
Implementation Method 1
a highly-efficient fluorescent organic EL device using thermally activated delayed fluorescence (hereinafter simply referred to as "delayed fluorescence" in some cases) has been proposed and studied
Implementation Method 2
When a voltage is applied to an organic electroluminescence device (hereinafter, occasionally referred to as "organic EL device"), holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected electrons and holes are recombined in the emitting layer to form excitons.
Data Source
AI summary
An organic electroluminescence device includes an anode, a cathode, and an emitting layer, in which the emitting layer contains a first compound represented by a formula (1) and a delayed fluorescent second compound represented by a formula (2), and singlet energy S1(M1) of the first compound and singlet energy S1(M2) of the second compound satisfy a relationship of Numerical Formula 1, S1(M2)>S1(M1) (Numerical Formula 1). In the formula, rings A, B, D, E, and F are each independently a cyclic structure selected from the group consisting of a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms and a 10 substituted or unsubstituted heterocyclic ring having 5 to 30 ring atoms; one or both of the rings B and D are present; and one or both of the rings E and F are present