OLED Emissive Layer Using Hole Scavengers for Narrow Emission
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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
Incorporating excitation energy transfer components, hole scavengers, and small full width at half maximum (FWHM) emitters in the light-emitting layers, with specific orbital energy relationships, to enhance energy transfer and emission efficiency, resulting in a narrow emission spectrum suitable for achieving the desired color gamut and improved device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphorescence emitters based on transition metals are used, then good efficiency and long lifetime are achieved, but color purity is poor due to broad emission spectrum
Solution Approach 1:
The patent introduces an energy pump component as an intermediary that absorbs energy from excitons and transfers it to the fluorescent emitter. This mediator enables the system to achieve narrow emission spectrum (good color purity) while maintaining high efficiency and long lifetime through the energy transfer mechanism, resolving the contradiction between phosphorescence performance and color purity.
Solution Approach 2:
The patent changes the emission mechanism from phosphorescence (broad spectrum) to fluorescence (narrow spectrum) by introducing a fluorescent emitter with specific HOMO-LUMO energy gap. This parameter change in the emission type achieves narrow FWHM (≤0.25 eV) for BT-2020 color gamut compliance while using an energy pump to maintain efficiency.
2Use of energy by moving object
If fluorescence emitters with narrow emission spectrum are used, then good color purity is achieved, but efficiency and lifetime are poor due to roll-off behavior and exciton annihilation
Solution Approach 1:
The energy pump acts as a mediator that captures excitons and transfers energy to the fluorescent emitter, preventing direct exciton-polaron annihilation and exciton-exciton annihilation. This intermediary mechanism maintains high efficiency and long lifetime while the fluorescent emitter provides narrow emission spectrum for good color purity.
Solution Approach 2:
The patent segments the emission function into two components: an energy pump (TADF or phosphorescence material) responsible for efficient energy capture and transfer, and a fluorescent emitter responsible for narrow spectrum emission. This functional segmentation allows each component to optimize its role, achieving both high efficiency and good color purity.
3Use of energy by moving object
If transition metal based phosphorescence materials are used, then good efficiency is achieved, but cost is high due to low abundance
Solution Approach 1:
The patent replaces expensive transition metal-based phosphorescence materials with organic fluorescent emitters that are cheaper and more abundant. The energy pump component can be TADF materials or small amounts of phosphorescence materials, significantly reducing transition metal content while maintaining efficiency through the energy transfer mechanism.
Solution Approach 2:
The energy pump serves as an intermediary that enables the use of cheap fluorescent emitters while maintaining high efficiency. This mediator allows the system to achieve good efficiency without relying on expensive transition metals, thus reducing cost while preserving performance.
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 solution achieves an organic electroluminescent device with a long lifetime, high quantum yield, and narrow emission, effectively targeting the BT-2020 and DCPI3 color gamut while reducing the reliance on expensive transition metals.
Implementation Method 1
one or more excitation energy transfer components EET-1... Herein, EET-1 and in some embodiments also Hscav may transfer excitation energy to one or more small full width at half maximum (FWHM) emitters SB
Implementation Method 2
one or more hole scavengers Hscav... Hscav may transfer excitation energy to one or more small full width at half maximum (FWHM) emitters SB
Implementation Method 3
one or more small full width at half maximum (FWHM) emitters SB... displaying a rather narrow emission spectrum, which exhibits an FWHM of the emission spectrum, which is typically smaller than or equal to 0.25 eV
Implementation Method 4
The energy pump may for example be a TADF material displaying reversed-intersystem crossing (RISC)
Data Source
AI summary
The present invention relates to organic electroluminescent devices comprising one or more light-emitting layers B, each of which is composed of one or more sublayers comprising as a whole one or more excitation energy transfer components EET-1, one or more hole scavengers Hscav, one or more small full width at half maximum (FWHM) emitters SB emitting light with an FWHM of less than or equal to 0.25 eV. Furthermore, the present invention relates to a method for generating light by means of an organic electroluminescent device according to the present invention.