OLED Light-Emitting Layer for Stable TADF-MR Fluorescence
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Solution Overview
Problem
The existing OLED devices with TADF-sensitized fluorescence materials face issues of low device life and unstable emission spectrum due to high-energy triplet excitons not being converted into singlet excitons in time, leading to inefficient energy transfer and emission mechanisms.
Innovation Solution
Incorporating a phosphorescent material and a multiple resonance fluorescent material into the light-emitting layer, along with a TADF material, to convert triplet excitons into singlet excitons and stabilize the emission spectrum through synergistic energy transfer, reducing the quantity of triplet excitons and enhancing device efficiency and life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If TADF material is used to convert triplet excitons into light, then color purity is improved, but device life deteriorates due to prolonged high-energy state
Solution Approach 1:
The patent introduces a phosphorescent material as an intermediary between the TADF material and the multiple resonance fluorescent material. The phosphorescent material accepts triplet excitons from the TADF material and transfers them to the multiple resonance fluorescent material, preventing the TADF material from remaining in a prolonged high-energy state while maintaining color purity through the multiple resonance fluorescent material's narrow spectrum emission
Solution Approach 2:
The patent creates a composite light-emitting layer combining TADF material, phosphorescent material, and multiple resonance fluorescent material. This composite structure enables synergistic energy transfer: TADF material generates triplet excitons, phosphorescent material mediates energy transfer, and multiple resonance fluorescent material emits narrow-spectrum light, simultaneously improving color purity and device life
2Illumination intensity
If multiple resonance fluorescent material is added for narrow spectrum emission, then color purity is improved, but energy transfer efficiency deteriorates due to mismatched energy levels
Solution Approach 1:
The phosphorescent material serves as an energy level bridge, with its triplet energy level positioned between the TADF material's triplet energy level and the multiple resonance fluorescent material's singlet energy level. This intermediary structure enables efficient stepwise energy transfer: TADF triplet excitons → phosphorescent triplet state → multiple resonance fluorescent singlet excitons, solving the energy level mismatch problem
Solution Approach 2:
The patent optimizes the energy level parameters of the phosphorescent material to match both the TADF material and multiple resonance fluorescent material. By carefully selecting phosphorescent materials with appropriate triplet energy levels and adjusting their concentrations, the system achieves efficient energy transfer while maintaining narrow-spectrum emission from the multiple resonance fluorescent material
3Productivity
If TADF and fluorescence emission mechanisms coexist, then light emission efficiency is improved, but emission spectrum stability deteriorates
Solution Approach 1:
The patent converts the potentially harmful effect of dual emission mechanisms into a benefit by using the phosphorescent material to quench TADF emission. The phosphorescent material accepts triplet excitons from the TADF material through Dexter energy transfer, suppressing TADF luminescence while directing energy to the multiple resonance fluorescent material, thereby eliminating spectral instability while maintaining high emission efficiency
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 combination of phosphorescent and multiple resonance fluorescent materials with TADF materials improves the conversion of triplet excitons to singlet excitons, stabilizes the emission spectrum, and increases the efficiency and lifespan of OLED devices by effectively managing exciton levels and energy transfer.
Implementation Method 1
the triplet excitons may be transferred to the singlet energy level of the multiple resonance fluorescent material
Implementation Method 2
the multiple resonance fluorescent material may convert the triplet excitons into singlet excitons
Implementation Method 3
the TADF material transfers the energy to the fluorescent material through the Foster mechanism
Implementation Method 4
the triplet excitons are transferred to the fluorescent material through the Dexter energy
Data Source
AI summary
A light-emitting layer, a light-emitting device and a light-emitting apparatus are provided. The light-emitting layer includes a thermally activated delayed fluorescence (TADF) material, a phosphorescent material, a multiple resonance fluorescent material and a host material.