OLED Emitter Layer with Dual Delayed Fluorescent Dopants
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Solution Overview
Problem
Organic light emitting diodes (OLEDs) face challenges with low luminous efficiency and lifespan, particularly with blue luminous materials, which affect color purity and overall performance in display devices.
Innovation Solution
The use of an OLED structure incorporating first and second delayed fluorescent dopants with specific energy level relationships in the emitting material layer, where the excited state triplet energy levels and molecular orbital energy levels are carefully aligned to enhance exciton energy transfer and reduce hot triplet exciton formation, thereby improving luminous efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If blue phosphorescent materials are used in OLEDs, then color purity is improved, but luminous efficiency and lifespan deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the energy level relationships between host and dopant materials. Specifically, it sets the triplet energy level difference between first and second delayed fluorescent dopants within 0.1-0.5 eV, and controls HOMO/LUMO energy level differences greater than 0.03 eV and 0.05 eV respectively. These parameter optimizations enable efficient exciton energy transfer while preventing harmful hot triplet exciton accumulation, thereby simultaneously achieving high color purity and extended device lifespan.
Solution Approach 2:
The patent employs composite materials by creating a multi-component emitting layer system comprising a host material and two different delayed fluorescent dopants with complementary energy level characteristics. This composite structure allows the first dopant to emit blue light with high color purity while the second dopant acts as an energy transfer mediator, collectively achieving both high color purity and improved reliability through synergistic material combination.
2Illumination intensity
If blue phosphorescent materials are used in OLEDs, then color purity is improved, but luminous efficiency deteriorates
Solution Approach 1:
The patent introduces an intermediary mechanism by utilizing the second delayed fluorescent dopant as an energy transfer mediator. The second dopant receives triplet excitons from the host material and transfers them to the first dopant, which then emits blue light. This intermediary energy transfer pathway efficiently utilizes triplet excitons that would otherwise be lost, thereby improving luminous efficiency while maintaining high color purity through the first dopant's emission characteristics.
3Device complexity
If conventional emitting material layers are used, then device structure is simple, but exciton energy transfer is inefficient
Solution Approach 1:
The patent applies local quality by assigning different functional roles to different dopant materials within the emitting layer. The first delayed fluorescent dopant is specifically optimized for blue light emission with appropriate triplet energy level, while the second delayed fluorescent dopant is optimized for energy transfer with lower triplet energy level. This localized functional differentiation within the emitting layer enables efficient exciton energy transfer to the first dopant while maintaining a relatively simple overall 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
This configuration significantly enhances luminous efficiency, extends the lifespan of the OLED, and improves color purity by effectively utilizing both singlet and triplet excitons in the emission process, addressing the limitations of previous blue phosphorescent materials.
Implementation Method 1
the first emitting material layer includes a first host, a first delayed fluorescent dopant and a second delayed fluorescent dopant
Implementation Method 2
an excited state triplet energy level (T1TD1) of the first delayed fluorescent dopant and an excited state triplet energy level (T1TD2) of the second delayed fluorescent dopant satisfy the following relationship
Implementation Method 3
wherein an excited state triplet energy level (T1TD1) of the first delayed fluorescent dopant and an excited state triplet energy level (T1TD2) of the second delayed fluorescent dopant satisfy the following relationship in Equation (1)
Data Source
AI summary
An organic light emitting diode including a plurality delayed fluorescent materials with specific energy levels and an organic light emitting device including the diode is disclosed. When the plurality delayed fluorescent materials with specific energy levels are applied in an emitting material layer, it is possible to minimize the energy loss or exciton quenching during luminous process and to prevent the diode from reducing life span caused by the exciton quenching. When the emitting material layer includes other luminous material having a narrow FWHM, the organic light emitting diode can enhance its color purity.