OLED Light-Emitting Layer Using TADF Mediation for Narrow Color Emission
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Solution Overview
Problem
Existing organic electroluminescent devices struggle to combine high efficiency, long lifetime, and good color purity, particularly in achieving the BT-2020 and DCPI3 color gamut, due to broad emission spectra and high costs associated with transition metal-based phosphorescence materials.
Innovation Solution
An organic electroluminescent device comprising a light-emitting layer with a combination of a host material, a phosphorescence material, a small full width at half maximum (FWHM) emitter, and optionally a thermally activated delayed fluorescence (TADF) material, which together provide narrow emission spectra and efficient energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescence materials based on transition metals are used, then high efficiency is achieved, but cost increases and lifetime decreases
Solution Approach 1:
The patent introduces TADF materials as intermediary components that facilitate energy transfer from phosphorescence materials to fluorescence emitters. This mediator approach allows the system to leverage the high efficiency of phosphorescence materials while achieving the long lifetime and narrow emission spectrum of fluorescence materials, thereby resolving the contradiction between efficiency and lifetime
Solution Approach 2:
The invention creates a composite light-emitting layer combining phosphorescence materials, TADF materials, and fluorescence emitters. This composite structure integrates the advantages of different material types: the high efficiency of phosphorescence materials, the long lifetime of fluorescence materials, and achieves narrow emission spectra, thus resolving the contradiction between efficiency and lifetime
2Use of energy by moving object
If phosphorescence materials based on transition metals are used, then high efficiency is achieved, but cost increases
Solution Approach 1:
The patent replaces expensive transition metal-based phosphorescence materials with organic TADF materials and fluorescence emitters that are cheaper and more abundant. While phosphorescence materials provide initial energy conversion, the TADF and fluorescence components enable sustained emission without requiring continuous high concentrations of expensive metals, thereby reducing manufacturing cost while maintaining efficiency
3Manufacturing precision
If fluorescence or TADF emitters with narrow emission spectrum are used, then color purity is improved, but efficiency decreases
Solution Approach 1:
The patent employs phosphorescence materials and TADF materials as preliminary energy pumps that convert electrical energy to optical energy efficiently. These materials perform the energy conversion action in advance, transferring energy to the fluorescence emitter which then produces the narrow emission spectrum. This preliminary energy conversion approach ensures high overall efficiency while achieving pure colors
Solution Approach 2:
TADF materials serve as intermediary energy transfer mediators between the phosphorescence materials and fluorescence emitters. They receive energy from phosphorescence materials and transfer it to fluorescence emitters, enabling efficient energy utilization while maintaining the narrow emission spectrum and high color purity of the fluorescence emitter
4Manufacturing precision
If fluorescence or TADF emitters with narrow emission spectrum are used, then color purity is improved, but lifetime decreases
Solution Approach 1:
Phosphorescence materials and TADF materials act as protective intermediaries that handle the harsh electrical-to-optical energy conversion process. By mediating this conversion, they protect the fluorescence emitter from direct electrical stress, exciton-polaron annihilation, and exciton-exciton annihilation, thereby extending the lifetime of the fluorescence emitter while maintaining its narrow emission spectrum and high color purity
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 device achieves a long lifetime, high quantum yield, and narrow emission suitable for the BT-2020 and DCPI3 color gamut, while reducing the reliance on expensive transition metals.
Implementation Method 1
Herein, a phosphorescence material and/or an optional TADF material might transfer energy to a small full width at half maximum (FWHM) emitter displaying emission of light
Implementation Method 2
a phosphorescence material, a small full width at half maximum (FWHM) emitter, a host material, and a TADF material
Implementation Method 3
a small full width at half maximum (FWHM) emitter, a host material, and a TADF material
Implementation Method 4
a phosphorescence material and/or an optional TADF material might transfer energy to a small full width at half maximum (FWHM) emitter
Implementation Method 5
Organic electroluminescent devices containing one or more light-emitting layers based on organics such as, e.g. organic light-emitting diodes (OLEDs)
Data Source
AI summary
The present invention relates to a an organic electroluminescent device comprising at least one light-emitting layer B composed of one or more sublayers, wherein the one or more sublayers of the light-emitting layer B as a whole comprise at least one host material HB, at least one phosphorescence material PB, at least one small FWHM emitter SB, and optionally at least one TADF material EB, wherein SB emits light with a full width at half maximum (FWHM) of less than or equal to 0.25 eV.