Blue Phosphorescent OLED Host Material Stability
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Solution Overview
Problem
Current organic electroluminescence devices using blue phosphorescence face challenges in achieving high luminous efficiency, low operating voltage, long emission life, and ageing stability, particularly in the wet process production method, where host materials and electron-transporting materials have unsatisfactory solubility and solution stability, leading to issues like voltage rise and reduced brightness over time.
Innovation Solution
Incorporating a blue phosphorescent organic metal complex with a specific structure and a host compound having a particular molecular structure, represented by Formulas (1) and (H1), which enhances carrier transport and stability, allowing for efficient light emission and reduced voltage rise, while being suitable for the wet process production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional host materials and electron-transporting materials are used in wet process production, then device fabrication is simplified, but solubility and solution stability are unsatisfactory leading to voltage rise and reduced brightness over time
Solution Approach 1:
The patent modifies the molecular structure of host materials by introducing specific functional groups (such as dibenzofuran, dibenzothiophene, and their derivatives) to alter solubility parameters and solution stability. These structural changes enable the materials to maintain stability during wet process fabrication while preventing voltage rise and brightness degradation over time, thus resolving the contradiction between ease of manufacture and reliability.
2Use of energy by moving object
If blue phosphorescent compounds with high triplet excitation energy are used, then luminous efficiency is improved, but emission life is deteriorated
Solution Approach 1:
The patent employs composite material systems where blue phosphorescent compounds (such as FIrpi and its derivatives) are combined with specifically designed host materials. This composite approach allows the phosphorescent compound to maintain high triplet excitation energy for efficient luminous output, while the host material provides a stable environment that extends emission life by preventing degradation, thus resolving the contradiction between luminous efficiency and emission life.
3Use of energy by stationary object
If operating voltage is reduced for energy efficiency, then power consumption decreases, but luminous efficiency and emission life become insufficient
Solution Approach 1:
The patent optimizes the energy level parameters of both host and phosphorescent materials to achieve a balanced operating voltage. By carefully selecting materials with appropriate HOMO-LUMO levels and triplet energy states, the device can operate at reduced voltage for lower power consumption while maintaining sufficient luminous efficiency and emission life through the synergistic material combination.
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 proposed solution achieves high luminous efficiency, low operating voltage, and extended emission life, along with improved ageing stability, making the organic electroluminescence devices more suitable for practical applications, including display and lighting equipment.
Implementation Method 1
An organic electroluminescence device making use of phosphorescence emitted in an excited triplet state is reported from Princeton University
Implementation Method 2
a hole injected from an anode and an electron injected from a cathode are recombined in the light-emitting layer by applying an electric field, whereby an exciton is formed, and light (fluorescence and phosphorescence) discharged when the above exciton is deactivated is used
Data Source
AI summary
Provided are an organic electroluminescence device which has a high luminous efficiency, a low operating voltage and a long life and which is low in a voltage rise in operation and excellent in an ageing stability and has an aptitude in production by the wet process, and a lighting equipment and a display device which are prepared by using the same.The above organic electroluminescence device is constituted from organic layers including at least a light-emitting layer which are interposed between an anode and a cathode, wherein at least one layer of the above organic layers contains a blue phosphorescent organic metal complex having a structure represented by the following Formula (1) and a compound represented by the following Formula (H1):