Organic EL Element Host-Dopant Reorganization Energy Control
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Solution Overview
Problem
Current organic electroluminescence elements face challenges in achieving low driving voltage, high luminous efficiency, long-term durability, reduced dark spots, and high retention of coating solution, while maintaining optimal structural changes between ground and excited states to minimize non-radiative deactivation.
Innovation Solution
Incorporating a luminescent dopant with a reorganization energy of 0 eV to 0.7 eV in electron transition from the ground state to the lowest excited triplet state, combined with a host compound having a reorganization energy of 0 eV to 0.3 eV in electron transfer reactions, and a molecular weight within 500 to 3000, to enhance carrier transfer and reduce structural changes, thereby improving luminous efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphorescent dopants with high radiative rate constant are used to enhance luminescent property, then luminous efficiency is improved, but structural changes between ground and excited states increase leading to higher non-radiative deactivation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the reorganization energy of the host compound to fall within 0.01-0.30 eV and the dopant-to-host concentration ratio to be 0.01-0.10. This optimization of physical parameters minimizes structural changes during electron transition while maintaining high radiative rate constant, thereby resolving the contradiction between improving luminous efficiency and reducing non-radiative deactivation
Solution Approach 2:
The patent implements local quality by selecting specific host compounds with particular molecular structures (such as mCP, TCTA, TAPC) that provide localized steric control and appropriate energy levels. These locally optimized host environments enable the phosphorescent dopant to achieve high radiative rate constant while maintaining minimal structural reorganization, thus reducing non-radiative deactivation pathways
2Loss of energy
If host compounds with low reorganization energy are used to reduce structural changes, then non-radiative deactivation is reduced, but carrier transfer efficiency may be compromised
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the reorganization energy of host compounds to a specific range (0.01-0.30 eV) and adjusting the dopant-to-host concentration ratio (0.01-0.10). These parameter optimizations ensure that carrier transfer remains efficient while structural changes are minimized, preventing non-radiative deactivation
Solution Approach 2:
The patent employs composite materials by creating a luminous layer that combines phosphorescent dopants (such as iridium complexes) with specifically selected host compounds (mCP, TCTA, TAPC). This composite structure leverages the complementary properties of both components: the host provides low reorganization energy and appropriate carrier transport, while the dopant provides high radiative efficiency, thus simultaneously achieving efficient carrier transfer and reduced non-radiative deactivation
3Ease of manufacture
If conventional host compounds are used in organic EL elements, then manufacturing is simplified, but dark spots appear and coating solution retention is poor
Solution Approach 1:
The patent applies parameter changes by optimizing the reorganization energy parameter of host compounds to 0.01-0.30 eV and controlling the dopant-to-host concentration ratio within 0.01-0.10. These parameter optimizations improve coating solution retention and eliminate dark spots while maintaining manufacturing simplicity, as the optimized parameters work effectively with conventional fabrication processes
Solution Approach 2:
The patent uses composite materials by formulating a luminous layer with specific phosphorescent dopants combined with optimized host compounds. This composite formulation improves coating solution retention and eliminates dark spot defects while maintaining ease of manufacture, as the composite materials can be processed using standard organic EL fabrication techniques
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 results in an organic electroluminescence element with low driving voltage, high luminous efficiency, long-term durability, reduced dark spots, and improved retention of coating solution, by minimizing non-radiative deactivation and optimizing structural changes in the luminous layer.
Implementation Method 1
a luminescent dopant having a reorganization energy of 0 eV to 0.7 eV in the electron transition from the ground state (S0) to the lowest excited triplet state (T1)
Implementation Method 2
In the organic EL element, electrons and holes are injected into the luminous layer to recombine therein, which generates excitons. The excitons are deactivated while emitting light. The organic EL element emits light (fluorescence or phosphorescence) in such a manner.
Data Source
AI summary
An organic electroluminescence element includes: an anode; a cathode; and a luminous layer. The luminous layer includes: a luminescent dopant having a reorganization energy of 0 eV to 0.7 eV in electron transition from a ground state (S0) to a lowest excited triplet state (T1); and a host compound having a reorganization energy of 0 eV to 0.3 eV in electron transfer reaction between a ground state (S0) and an anionic radical state (AR), and having a molecular weight within a range of 500 to 3000.