OLED Emissive Layer with Narrow FWHM Emitter for Color Purity
Find Innovative SolutionsGenerate Solutions
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 out-coupling efficiency losses in top-emitting devices, and the high cost of transition metal-based phosphorescence materials.
Innovation Solution
An organic electroluminescent device comprising a light-emitting layer with 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, where the FWHM emitter emits light with a width of less than or equal to 0.25 eV, facilitating energy transfer and improving emission characteristics.
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 due to low abundance of transition metals
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 these materials have shorter operational lifetimes but achieving cost reduction as the primary goal
Solution Approach 2:
The patent changes the material type from inorganic phosphorescence to organic fluorescence/TADF, altering the emission mechanism while maintaining acceptable performance through molecular design optimization
2Use of energy by moving object
If phosphorescence emitters with broad emission spectrum are used, then high efficiency is achieved, but color purity deteriorates and out-coupling efficiency losses increase
Solution Approach 1:
The patent fundamentally changes the emission spectrum parameter by selecting fluorescence or TADF emitters with inherently narrow emission bands (FWHM ≤ 0.25 eV), achieving both high color purity and acceptable efficiency through molecular design
3Manufacturing precision
If fluorescence or TADF emitters with narrow emission spectrum are used, then color purity is improved, but efficiency and lifetime deteriorate due to roll-off behavior and exciton annihilation
Solution Approach 1:
The patent uses very low dopant concentrations (0.1-5 wt%) of fluorescence/TADF emitters in the light-emitting layer, applying just enough to achieve narrow emission while minimizing exciton annihilation effects that cause efficiency roll-off
Solution Approach 2:
The patent introduces host materials as intermediaries that facilitate energy transfer to the guest emitters, enabling efficient light emission while the host matrix protects against exciton-polaron and exciton-exciton annihilation
4Manufacturing precision
If top emitting device structure is used, then color coordinate adjustment is achieved, but out-coupling efficiency losses increase due to broad emission spectrum
Solution Approach 1:
The patent changes the emission spectrum parameter to narrow bandwidth (FWHM ≤ 0.25 eV), which simultaneously improves color purity and reduces out-coupling losses by better matching the spectral response of human vision and display standards
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
at least one phosphorescence material P B
Implementation Method 2
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 3
at least one thermally activated delayed fluorescence (TADF) material E B
Implementation Method 4
The energy pump may for example be a TADF material displaying reversed-intersystem crossing (RISC)
Implementation Method 5
When a voltage (and electrical current) is applied to an organic electroluminescent device, holes and electrons are injected from an anode and a cathode, respectively. Excitons of high energy are then generated by recombination of the holes and the electrons in a light-emitting layer
Data Source
AI summary
The 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.