OLED Emitter Layer Segmentation for Efficiency and Lifetime
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Solution Overview
Problem
Current organic light emitting diodes (OLEDs) face limitations in luminous efficiency and color purity, particularly with blue phosphorescent materials having short lifetimes and poor reliability, and delayed fluorescent materials exhibiting low luminous lifetime and broad emission spectra, which hinder their application in display devices.
Innovation Solution
The development of an OLED with a multiple-layered emitting material layer structure, incorporating a first emitting material layer with a delayed fluorescent dopant and a second emitting material layer with a fluorescent or phosphorescent dopant, where the energy levels of the host and dopant materials are optimized to enhance exciton energy transfer and improve color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If blue phosphorescent materials are used in the emitting material layer, then luminous efficiency is improved, but luminous lifetime is shortened and reliability deteriorates
Solution Approach 1:
The emitting material layer is divided into multiple sub-layers with different functions: a first emitting sub-layer containing delayed fluorescent material for extending lifetime, and a second emitting sub-layer containing phosphorescent material for maintaining high luminous efficiency. This segmentation allows each layer to optimize for its specific function while working together to resolve the contradiction between efficiency and lifetime.
Solution Approach 2:
The patent employs a composite emitting material layer structure combining delayed fluorescent materials and phosphorescent materials with carefully matched energy levels. The delayed fluorescent material acts as an energy transfer mediator that receives energy from excitons and transfers it to the phosphorescent material, creating a synergistic system that achieves both high efficiency and extended lifetime.
2Duration of action of stationary object
If delayed fluorescent materials are used in the emitting material layer, then luminous lifetime is extended, but color purity deteriorates due to broad emission spectra
Solution Approach 1:
Different regions of the emitting material layer are assigned different material compositions: the first emitting sub-layer uses delayed fluorescent material optimized for lifetime extension, while the second emitting sub-layer uses phosphorescent material optimized for color purity. This local quality differentiation allows each region to excel at its primary function while the overall structure achieves both goals simultaneously.
Solution Approach 2:
The delayed fluorescent material serves as an intermediary that receives exciton energy and transfers it to the phosphorescent material through energy transfer. This mediator approach allows the system to benefit from the long lifetime of delayed fluorescent materials while achieving the narrow emission spectra and high color purity of phosphorescent materials in the final light output.
3Device complexity
If a single emitting material layer is used, then device complexity is reduced, but luminous efficiency and color purity cannot be simultaneously optimized
Solution Approach 1:
The emitting material layer is segmented into multiple functional sub-layers, each optimized for specific performance characteristics. This segmentation enables simultaneous optimization of luminous efficiency and color purity while maintaining a relatively simple overall device structure that can be manufactured using standard OLED processes.
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 maximizes luminous efficiency and color purity, enabling the OLED to achieve hyper-fluorescence with improved reliability and extended lifetime, suitable for display devices.
Implementation Method 1
the energy levels of the host and dopant materials are optimized to enhance exciton energy transfer and improve color purity
Implementation Method 2
a first emitting material layer with a delayed fluorescent dopant and a second emitting material layer with a fluorescent or phosphorescent dopant
Implementation Method 3
holes injected from the anode and electrons injected from the cathode are combined in the EML to form excitons at an unstable energy state, and then emit light as the exciton drops to the stable ground state
Data Source
AI summary
An organic light emitting diode comprises an emitting material layer implementing a delayed fluorescence and another emitting material layer disposed adjacently to the emitting material layer and implementing fluorescence or phosphorescence and an organic light emitting device including the diode. As exciton generated in the plural emitting material layer drops to a ground state through the luminous materials each of which has a controlled energy level, it is possible to implement excellent luminous efficiency derived from a delayed fluorescent material and improved color purity derived from a fluorescent or phosphorescent material having narrow FWHM.