OLED Emissive Layer Using TTA Host to Lower Voltage
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Solution Overview
Problem
Existing organic electroluminescent devices face challenges with low efficiency, high driving voltage, and stability issues due to the limitations of traditional fluorescent and phosphorescent materials, and the narrow evaporation window and complex process requirements of Multi-Resonance (MR) materials.
Innovation Solution
Incorporating a triplet-triplet annihilation type host material and a fluorescent dye with specific structures, such as Formula (1-2), (1-3), (1-6), or (2-3), to enhance exciton utilization, reduce triplet exciton concentration, and inhibit intermolecular interactions, thereby improving luminescence efficiency and driving voltage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional phosphorescent material is used in the light-emitting layer, then luminescence efficiency is improved, but cost increases and stability deteriorates
Solution Approach 1:
The patent changes the material parameters by using TADF emitters with specific triplet energy levels (ET > 2.1 eV) and adjusting the host-guest energy level matching. This allows achieving high luminescence efficiency through reverse intersystem crossing mechanism while avoiding the stability issues of traditional phosphorescent materials, resolving the contradiction between efficiency and stability.
Solution Approach 2:
The patent employs composite material systems combining TADF emitters (e.g., BPhen, Bpy-OXD derivatives) with specific host materials (e.g., mCP, TCTA, TAPC). This composite approach enables efficient triplet exciton utilization through energy level matching while maintaining device stability, overcoming the limitations of single-material systems.
2Quantity of substance
If traditional fluorescent material is used in the light-emitting layer, then cost is reduced, but luminescence efficiency deteriorates to extremely low levels
Solution Approach 1:
The patent fundamentally changes the emission mechanism parameter from conventional fluorescent singlet exciton utilization to TADF triplet exciton utilization through reverse intersystem crossing. This parameter change enables achieving high luminescence efficiency (external quantum efficiency > 20%) with fluorescent materials, closing the efficiency gap with phosphorescent materials while maintaining cost advantages.
3Use of energy by moving object
If Multi-Resonance (MR) material is used to achieve high efficiency and narrow-band emission, then device performance is improved, but evaporation window narrows and process complexity increases
Solution Approach 1:
The patent changes the emitter type parameter from MR materials to TADF materials, which have broader evaporation windows and simpler processing requirements. The TADF mechanism with adjustable triplet energy levels maintains high efficiency and narrow-band emission capabilities while significantly reducing process complexity and expanding manufacturing feasibility.
4Use of energy by moving object
If triplet exciton concentration is increased to improve luminescence efficiency, then efficiency is improved, but driving voltage increases
Solution Approach 1:
The patent changes the triplet exciton utilization mechanism parameter by implementing reverse intersystem crossing in TADF emitters. This mechanism converts triplet excitons to singlet excitons efficiently, achieving high luminescence efficiency with reduced triplet exciton accumulation. The improved exciton management reduces non-radiative recombination and lowers driving voltage, resolving the contradiction between efficiency and power consumption.
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 high luminescence efficiency and stability by effectively utilizing triplet excitons, reducing triplet exciton concentration, and inhibiting Dexter energy transfer, resulting in improved efficiency and lower driving voltage.
Implementation Method 1
a triplet-triplet annihilation type host and a fluorescent dye
Implementation Method 2
the fluorescent dye with a structure represented by the following Formula (1-2), (1-3), (1-6) or (2-3)
Implementation Method 3
When applying an appropriate voltage, electrons and holes are combined in the organic light-emitting layer to produce excitons and emit light
Implementation Method 4
the traditional fluorescent material and a traditional phosphorescent material
Data Source
AI summary
The present application provides an organic electroluminescent device and a display apparatus. The organic electroluminescent device includes a light-emitting layer, including a triplet-triplet annihilation type host and a fluorescent dye, where the fluorescent dye has a structure represented by the following Formula (1) or Formula (2). When the fluorescent dye in the light-emitting layer of the organic electroluminescent device of the present application combines with the triplet-triplet annihilation type host, the voltage of the device can be reduced, and the luminescence efficiency of the device can be improved.