OLED Energy-Level Tuning in Emitting Layers and Electron Blocking Layer
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Solution Overview
Problem
Conventional fluorescent materials exhibit low luminous efficiency due to involvement of only singlet excitons, while phosphorescent materials have short luminous lifetime, making them unsuitable for commercial applications.
Innovation Solution
An organic light emitting diode (OLED) with multiple emitting material layers and an electron blocking layer, where the second compound in the emitting material layers and electron blocking layer have specific energy level relationships, enhancing luminous efficiency and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used to improve luminous efficiency, then luminous efficiency is improved, but luminous lifetime becomes too short for commercial applications
Solution Approach 1:
The emitting layer is divided into multiple layers (first emitting material layer and second emitting material layer) with different delayed fluorescent materials having different energy levels. This segmentation allows each layer to contribute differently to the overall luminescence, enabling both high efficiency and long lifetime by optimizing the energy level distribution across layers.
Solution Approach 2:
The patent changes the energy level parameters of the delayed fluorescent materials in different emitting layers. By controlling the energy levels (HOMO and LUMO levels) of the delayed fluorescent materials to satisfy specific relationships (Equation 1 and Equation 2), the device achieves both high luminous efficiency and extended luminous lifetime.
2Duration of action of moving object
If conventional fluorescent materials are used, then luminous lifetime is extended, but luminous efficiency remains low due to only singlet excitons involvement
Solution Approach 1:
The patent introduces delayed fluorescent materials as intermediaries between the host material and the electrodes. These delayed fluorescent materials facilitate the conversion of triplet excitons to singlet excitons through reverse intersystem crossing, enabling both high luminous efficiency (by utilizing both singlet and triplet excitons) and acceptable luminous lifetime.
Solution Approach 2:
The emitting layers are composed of composite materials including host materials and delayed fluorescent materials. This composite structure enables the system to utilize both singlet and triplet excitons for luminescence, achieving high luminous efficiency while maintaining reasonable luminous lifetime through the synergistic effects of the composite materials.
3Use of energy by moving object
If multiple emitting material layers with different energy levels are used, then luminous efficiency and lifetime are improved, but device complexity increases
Solution Approach 1:
The emitting layer is segmented into multiple layers with progressively increasing energy levels from the first to the second emitting material layer. This segmentation strategy systematically organizes the complexity while achieving improved luminous efficiency and lifetime through optimized energy level distribution.
Solution Approach 2:
The patent systematically changes the energy level parameters (HOMO and LUMO levels) of the delayed fluorescent materials in different layers according to specific relationships (Equation 1 and Equation 2). This parameter control approach manages device complexity by establishing clear design rules for material selection and layer configuration.
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 OLED achieves reduced driving voltage and improved luminous efficiency and lifetime by utilizing delayed fluorescent materials with controlled energy levels, enabling 100% internal quantum efficiency.
Implementation Method 1
each of the first emitting material layer and the second emitting material layer comprises a first compound and a second compound, wherein the second compound comprises an organic compound having the structure of Chemical Formula 1 or Chemical Formula 3
Implementation Method 2
enabling 100% internal quantum efficiency
Implementation Method 3
a HOMO (Highest Occupied Molecular orbital) energy level (HOMODF) of the second compound and a HOMO energy level (HOMOEBL) of the electron blocking layer satisfy the following relationship in Equation (1)
Implementation Method 4
when electrical charges are injected into an emitting material layer between an electron injection electrode (i.e., cathode) and a hole injection electrode (i.e., anode), electrical charges are recombined to form excitons, and then emit light as the recombined excitons are shifted to a stable ground state
Data Source
AI summary
The present disclosure relates to an organic light emitting diode (OLED) including plural light emitting material layers disposed between two electrodes and an electron blocking layer, wherein an energy level of the electron blocking layer disposed adjacently to an emitting material layer with relatively low level delayed fluorescent material and an energy level of the delayed fluorescent material are controlled, and an organic light emitting device having the diode. The OLED can lower its driving voltage and maximize its luminous efficiency and luminous lifetime.