OLED Light-Emitting Layer Host Material Energy Alignment
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Solution Overview
Problem
Existing OLEDs face challenges in achieving high emission efficiency and long emission lifetime due to limitations in the design of light-emitting layers, particularly in the management of excitation energies and the concentration of light-emitting materials.
Innovation Solution
The proposed light-emitting element incorporates a light-emitting layer with a specific composition, including a first host material with a larger band gap, a second host material with a lower triplet excitation energy level, and a first light-emitting material exhibiting thermally activated delayed fluorescence. This configuration optimizes the transfer of excitation energies and promotes efficient singlet exciton formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the concentration of light-emitting material is increased to improve emission efficiency, then emission efficiency is improved, but the lifetime of the light-emitting element deteriorates due to increased degradation
Solution Approach 1:
The patent introduces a second host material as an intermediary substance with specific energy level characteristics (triplet excitation energy level lower than the first host material) to facilitate efficient energy transfer to the light-emitting material. This mediator enables high emission efficiency while maintaining lower concentrations of the light-emitting material, thereby extending device lifetime.
Solution Approach 2:
The patent optimizes multiple parameters including the concentration ratio of first to second host material (greater than 1), the band gap relationship (first host material has larger band gap), and the energy level alignment (singlet excitation energy of light-emitting material lower than first host material, triplet excitation energy of second host material lower than first host material). These parameter changes enable efficient energy transfer pathways that achieve high emission efficiency without requiring high light-emitting material concentrations.
2Productivity
If the concentration of light-emitting material is increased to improve emission efficiency, then emission efficiency is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent creates a composite light-emitting layer system comprising three materials with specifically designed energy level relationships: first host material (larger band gap), second host material (lower triplet excitation energy), and light-emitting material (TADF or hyper-fluorescence). This composite structure achieves synergistic effects where each component performs a specific function, enabling high emission efficiency while distributing the functional requirements across multiple materials rather than relying on high concentration of a single light-emitting material.
3Productivity
If the energy levels are optimized to improve emission efficiency, then emission efficiency is improved, but the device complexity increases due to multiple material requirements
Solution Approach 1:
The patent segments the light-emitting layer into three distinct functional components with clearly defined energy level roles: (1) first host material with larger band gap and higher singlet excitation energy, (2) second host material with lower triplet excitation energy, and (3) light-emitting material with appropriate energy levels for TADF or hyper-fluorescence. This segmentation allows each material to be optimized independently for its specific function while maintaining overall system efficiency.
Solution Approach 2:
The patent assigns different local qualities (energy level characteristics) to different materials in the composite system. The first host material provides a larger band gap for stable charge transport, the second host material provides lower triplet energy for efficient energy transfer, and the light-emitting material provides the specific emission characteristics. This local quality differentiation enables each material to perform its optimal function without requiring high concentrations throughout the system.
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 approach results in high emission efficiency and significantly improved emission lifetime, enhancing the reliability of OLEDs without the need to increase the concentration of the light-emitting material.
Implementation Method 1
a first light-emitting material exhibiting thermally activated delayed fluorescence
Implementation Method 2
a triplet excitation energy level of the second host material is lower than a triplet excitation energy level of the first host material
Data Source
AI summary
A light-emitting element includes a pair of electrodes, and a light-emitting layer between the pair of electrodes, wherein the light-emitting layer includes a first host material, a second host material, and a first light-emitting material exhibiting thermally activated delayed fluorescence, a concentration of the first host material is greater than a concentration of the second host material in the light-emitting layer, a band gap of the first host material is larger than a band gap of the second host material, a singlet excitation energy level of the first light-emitting material is lower than a singlet excitation energy level of the first host material, and a triplet excitation energy level of the second host material is lower than a triplet excitation energy level of the first host material.