OLED Emissive Layer Using Delayed Fluorescence Mediator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional organic light emitting diodes (OLEDs) face limitations in luminous efficiency, color purity, and luminous lifespan, particularly due to the short lifespan of phosphorescent materials and the low efficiency of fluorescent materials that only utilize singlet excitons.
Innovation Solution
An OLED structure is developed with an emissive layer containing specific compounds, including a first compound with delayed fluorescent properties and a second compound with fluorescent properties, where the energy levels are adjusted to ensure proper exciton energy transfer, allowing for the utilization of both singlet and triplet excitons, thereby enhancing luminous efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used to improve luminous efficiency by utilizing triplet excitons, then luminous efficiency is improved, but luminous lifespan becomes too short for commercial application
Solution Approach 1:
The patent introduces a delayed fluorescent compound as an intermediary material in the emitting layer. This compound mediates between the phosphorescent dopant and the host material, enabling triplet excitons to be converted into delayed fluorescence emission. The delayed fluorescent compound acts as a bridge that transforms the harmful short-lived triplet states into useful long-lived delayed fluorescence, resolving the contradiction between utilizing triplet excitons for high efficiency and maintaining device lifespan.
Solution Approach 2:
The patent changes the emission mechanism parameter from conventional phosphorescence to delayed fluorescence by selecting specific compounds with appropriate energy levels. By adjusting the energy level parameters (HOMO, LUMO, singlet and triplet energy levels) of the host, dopant, and delayed fluorescent compound, the system achieves high luminous efficiency through triplet exciton utilization while extending luminous lifespan through the delayed fluorescence mechanism.
2Duration of action of stationary object
If fluorescent materials are used to maintain long luminous lifespan, then luminous lifespan is improved, but luminous efficiency decreases because only singlet excitons are utilized
Solution Approach 1:
The delayed fluorescent compound serves as a mediator that enables triplet exciton utilization while maintaining the fluorescent emission mechanism. Unlike conventional fluorescent materials that waste triplet excitons, the delayed fluorescent compound captures triplet excitons and converts them into delayed fluorescence through reverse intersystem crossing, thereby improving luminous efficiency without sacrificing lifespan.
Solution Approach 2:
The emitting layer is designed as a composite system containing host material, phosphorescent dopant, and delayed fluorescent compound. This composite structure combines the advantages of phosphorescent materials (triplet exciton utilization) with the advantages of fluorescent materials (long lifespan), achieving both high luminous efficiency and extended operational lifetime.
3Use of energy by moving object
If energy levels are adjusted to enable proper exciton energy transfer between compounds, then luminous efficiency is improved, but device complexity increases due to multiple compound requirements
Solution Approach 1:
The patent applies local quality by assigning specific functional roles to different compounds within the emitting layer. The host material provides the matrix and charge transport, the phosphorescent dopant provides triplet excitons, and the delayed fluorescent compound provides the emission mechanism. Each compound is optimized for its specific function with appropriate energy levels, achieving high overall efficiency while maintaining a manageable three-component 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
The solution significantly improves luminous efficiency, color purity, and lifespan of the OLED by effectively utilizing both singlet and triplet excitons, leading to enhanced performance in organic light emitting devices.
Implementation Method 1
the energy levels are adjusted to ensure proper exciton energy transfer, allowing for the utilization of both singlet and triplet excitons
Implementation Method 2
when electrical charges are injected into an emitting material layer between an electron injection electrode (i.e., cathode) and a hole injection electrode (i.e., anode), electrical charges are recombined to form excitons, and then emit light as the recombined excitons are shifted to a stable ground state
Data Source
AI summary
An organic light emitting diode (OLED) includes at least one emitting material layer (EML) disposed between two electrodes and including a first compound of a pyrimidine-based organic compound substituted with at least one electron-withdrawing group and a second compound of an organic compound having a tetracene-based core. The OLED can be included in an organic light emitting device. The first compound and the second compound can be the same emitting material layer or adjacently disposed emitting material layers. The OLED can lower its driving voltage and improve its luminous efficiency utilizing the advantages of the first and second compounds by adjusting energy levels between the first and second compounds.