OLED Emission Layer Composition for Narrow Spectrum and Long Lifetime
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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 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 material having specific energy level configurations, to enhance emission spectrum narrowness and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescence materials based on transition metals are used, then efficiency is improved, but cost increases and lifetime decreases
Solution Approach 1:
The patent introduces a TADF material as an intermediary between the phosphorescence material and the host material. This TADF material acts as a buffer that reduces direct interactions between excitons and phosphorescence materials, thereby decreasing exciton-polaron annihilation and exciton-exciton annihilation, which improves device lifetime while maintaining efficiency through the energy transfer mechanism from TADF to phosphorescence emitter
Solution Approach 2:
The patent creates a composite light-emitting layer combining host material, phosphorescence material, and TADF material with specific weight ratios (phosphorescence material 1-10 wt%, TADF material 5-50 wt%). This composite structure leverages the advantages of both phosphorescence materials (high efficiency) and TADF materials (reduced annihilation losses), achieving both high efficiency and long lifetime
2Use of energy by moving object
If phosphorescence materials are used, then efficiency is improved, but emission spectrum broadness increases
Solution Approach 1:
The patent applies local quality by having different materials serve different functions within the same light-emitting layer: the phosphorescence material provides high efficiency through triplet state utilization, while the TADF material with its narrow emission spectrum (FWHM ≤ 0.25 eV) provides the narrow spectral profile needed for color purity. The energy transfer from TADF to phosphorescence emitter creates a hybrid emission characteristic
3Ease of manufacture
If transition metal content is reduced, then cost decreases, but efficiency and lifetime are affected
Solution Approach 1:
The patent optimizes the concentration parameter of phosphorescence material to a specific range (1-10 wt%) and introduces TADF material at 5-50 wt%. This parameter optimization ensures sufficient phosphorescence emission for high efficiency while limiting excessive phosphorescence material that would increase cost and annihilation losses. The TADF material compensates for efficiency at these optimized low phosphorescence concentrations
4Ease of manufacture
If transition metal content is reduced, then cost decreases, but lifetime is affected
Solution Approach 1:
The TADF material serves as a protective intermediary that reduces direct exciton-phosphorescence material interactions. By having excitons primarily interact with TADF material instead of phosphorescence material, the annihilation processes (exciton-polaron and exciton-exciton) are suppressed, extending device lifetime even at reduced phosphorescence material concentrations that lower cost
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 a long lifetime, high quantum yield, 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
Incorporating a light-emitting layer composed of sublayers containing a host material, a phosphorescence material, a small full width at half maximum (FWHM) emitter
Implementation Method 3
a thermally activated delayed fluorescence (TADF) material, with each material having specific energy level configurations
Implementation Method 4
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 material having specific energy level configurations
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.