OLED Emissive Layer Stack Using Small-FWHM Emitters
Find Innovative SolutionsGenerate Solutions
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
Incorporating 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, with each emitter having specific energy levels and emission spectra less than 0.25 eV, to enhance energy transfer and achieve narrow emission.
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 and expensive materials
Solution Approach 1:
The patent replaces expensive, scarce transition metal-based phosphorescence materials with organic fluorescence or TADF emitters that are abundant and cost-effective. While these organic materials have shorter operational lifetimes, they provide a sustainable alternative that reduces manufacturing costs and dependency on rare materials.
Solution Approach 2:
The patent modifies the emission spectrum parameter by selecting organic emitters with narrow emission spectra (FWHM ≤ 0.25 eV). This parameter change enables the materials to achieve both high efficiency and color purity requirements for BT-2020 and DCPI3 color gamut while using abundant organic materials instead of expensive transition metals.
2Illumination intensity
If fluorescence or TADF emitters with narrow emission spectrum are used, then color purity is improved, but efficiency decreases due to roll-off behaviour at higher luminance
Solution Approach 1:
The patent employs composite material systems where organic fluorescence or TADF emitters are combined with carefully selected host materials. This composite approach creates energy transfer pathways that maintain narrow emission spectra for color purity while the host-guest interaction enhances efficiency and reduces roll-off behavior at high luminance.
Solution Approach 2:
The host material acts as an intermediary between the excitons generated in the light-emitting layer and the organic emitter. The host facilitates efficient energy transfer to the emitter while the emitter maintains its narrow emission spectrum, thus resolving the contradiction between efficiency and color purity.
3Illumination intensity
If top emitting devices are used to adjust color coordinate, then color purity is improved, but out-coupling efficiency is reduced due to broad emission spectrum
Solution Approach 1:
The patent fundamentally changes the emission spectrum parameter by using organic emitters with FWHM ≤ 0.25 eV, which is significantly narrower than conventional phosphorescence materials. This narrow emission spectrum enables top emitting devices to achieve both high color purity and high out-coupling efficiency, as the concentrated spectral energy can be more effectively coupled out through the device structure.
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 proposed configuration results in an organic electroluminescent device with improved efficiency, extended lifetime, and narrow emission suitable for achieving the BT-2020 and DCPI3 color gamut, while reducing the reliance on expensive transition metals.
Implementation Method 1
Herein, a phosphorescence material and/or a TADF material might transfer energy to a small full width at half maximum (FWHM) emitter displaying emission of light.
Implementation Method 2
at least one phosphorescence material P B
Implementation Method 3
at least one thermally activated delayed fluorescence (TADF) material E B
Implementation Method 4
Excitons of high energy are then generated by recombination of the holes and the electrons in a light-emitting layer. The decay of such excited states (e.g., singlet states such as S1 and/or triplet states such as T1 to the ground state (S0) desirably leads to the emission of light.
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.