OLED Emissive Layer Composition for Narrow Spectrum Color Purity
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Solution Overview
Problem
Existing organic electroluminescent devices struggle to achieve a balance of 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 composed of sublayers containing 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
1Reliability
If phosphorescence materials based on transition metals are used, then high efficiency and long lifetime are achieved, but cost increases and emission spectrum becomes broad
Solution Approach 1:
The patent replaces expensive transition metal-based phosphorescence materials with organic fluorescence or TADF emitters that are cheaper and more abundant, accepting that individual emitter molecules have limited operational life but achieving device longevity through continuous supply via energy transfer from TADF pump materials
Solution Approach 2:
The patent introduces TADF materials as intermediary pump substances that absorb electrical energy and transfer it to fluorescence emitters, enabling indirect excitation of the light-emitting species and allowing use of inexpensive organic materials instead of costly phosphorescence complexes
2Use of energy by moving object
If phosphorescence materials are used, then high efficiency is achieved, but emission spectrum becomes broad leading to low out-coupling efficiency
Solution Approach 1:
The patent changes the fundamental emission mechanism from phosphorescence with broad spectra to fluorescence with narrow spectra, and optimizes the FWHM parameter of the emission spectrum to be less than or equal to 0.25 eV, thereby improving out-coupling efficiency for top-emitting OLED structures targeting BT-2020 and DCPI3 color gamut
3Illumination intensity
If fluorescence or TADF emitters with narrow emission spectrum are used, then color purity and out-coupling efficiency are improved, but efficiency decreases at higher luminance
Solution Approach 1:
The patent employs TADF materials as pump substances that exhibit reversed-intersystem crossing to transfer energy to fluorescence emitters, creating a two-stage energy transfer system that maintains narrow emission spectrum for color purity while using the TADF pump to sustain high efficiency even at elevated luminance levels where direct fluorescence efficiency drops
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 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
a phosphorescence material, a small full width at half maximum (FWHM) emitter, a host material, and optionally a TADF material
Implementation Method 2
a phosphorescence material, a small full width at half maximum (FWHM) emitter, a host material, and optionally a TADF material
Implementation Method 3
which together provide narrow emission spectra and efficient energy transfer
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.