OLED Blue Emitter Tandem Structure for Exciton Distribution
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Solution Overview
Problem
Current OLEDs face challenges in achieving high luminous efficiency and long luminous lifespan while maintaining low power consumption and minimizing color changes with gradation, primarily due to issues with exciton recombination and material degradation.
Innovation Solution
The use of a tandem structure with two blue emitting material layers, each comprising a specific organic compound host with controlled energy levels and charge mobility, to uniformly distribute the exciton recombination zone and prevent exciton quenching, thereby minimizing color changes and enhancing luminous efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphorescent materials are used to improve luminous efficiency, then luminous efficiency is improved, but luminous lifespan becomes too short for commercial use
Solution Approach 1:
The patent changes the energy level parameters of the host materials in the emitting layer. By selecting hosts with specific HOMO and LUMO energy levels that form appropriate energy offsets with the electron blocking layer, the patent achieves both high luminous efficiency and extended lifespan without requiring phosphorescent materials.
Solution Approach 2:
The patent uses a composite structure consisting of multiple organic compound layers with different energy level characteristics. The combination of the electron blocking layer and the emitting layer with specific host materials creates a system that simultaneously achieves high efficiency and long operational life.
2Use of energy by stationary object
If voltage is reduced to lower power consumption, then power consumption is reduced, but luminous efficiency may be affected
Solution Approach 1:
The patent optimizes the energy level parameters of the organic compounds to enable efficient electron-hole recombination at lower voltages. By carefully selecting hosts with appropriate HOMO/LUMO levels, the device achieves high luminous efficiency even when operated at reduced voltages, thereby lowering power consumption.
3Device complexity
If single emitting layer is used to simplify structure, then device complexity is reduced, but color uniformity and luminous efficiency are compromised
Solution Approach 1:
The patent segments the emitting layer into multiple functional layers: an electron blocking layer and an emitting layer with specific host materials. This segmentation allows each layer to perform its specialized function optimally, achieving high luminous efficiency while maintaining relatively simple overall device structure.
4Device complexity
If exciton recombination is concentrated in one region to simplify design, then device complexity is reduced, but color changes with gradation increase
Solution Approach 1:
The patent applies local quality by creating different regions with specific properties: the electron blocking layer has high electron hole recombination capability, while the emitting layer has optimized energy levels for efficient exciton formation. This local differentiation ensures uniform color output across different brightness levels while maintaining simple device architecture.
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 approach results in improved luminous efficiency, extended lifespan, and reduced power consumption by uniformly distributing exciton recombination and preventing material degradation, while maintaining high-quality colors and low driving voltage.
Implementation Method 1
an organic light emitting diode that includes a first electrode; a second electrode facing the first electrode; and an emissive layer disposed between the first electrode and the second electrode, and including at least one emitting material layer
Implementation Method 2
The exciton recombination zone is formed uniformly within the emitting material layer irrespective of current density changes
Implementation Method 3
the first host has a highest occupied molecular orbital energy level higher than a highest occupied molecular orbital energy level of the electron blocking layer
Data Source
AI summary
An organic light emitting diode (OLED) and an organic light emitting device comprising the OLED (e.g., a display device or a lighting device) are described. The OLED can include a first blue emitting material layer including a first host, and a second blue emitting material layer including a second host, disposed between two electrodes. The OLED includes two blue emitting material layers so that an exciton recombination zone is distributed within the blue emitting material layers irrespective of current density or gradation. As the amount of non-emitting excitons accumulated outside of the emitting material layers is minimized, the driving voltage of the OLED can be lowered, and the luminous efficiency and the luminous lifespan of the OLED can be improved.