Blue Phosphorescence Compound Host Material for OLEDs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current organic light emitting diodes (OLEDs) suffer from reduced efficiency due to the low triplet energy level of commonly used host materials like carbazole biphenyl, leading to reverse energy transitions and heat absorption, which limits the effectiveness of phosphorescence-based light emission.
Innovation Solution
A blue phosphorescence compound with high triplet energy is used as the host material in the light emitting layer, specifically designed with symmetric or asymmetric substitutions on the dibenzofuran core, enhancing energy transfer and reducing reverse energy transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If carbazole biphenyl (CBP) is used as the host material, then the device can be manufactured with existing materials, but the triplet energy level is too low (2.6 eV) causing reverse energy transition and reduced efficiency
Solution Approach 1:
The patent changes the triplet energy level parameter of the host material from 2.6 eV (CBP) to above 2.9 eV by modifying the molecular structure. This parameter change prevents reverse energy transition to the phosphorescence dopant (Flrpic with triplet energy level of 2.9 eV) and maintains high emission efficiency while allowing continued use of standard manufacturing processes.
Solution Approach 2:
The patent creates a composite host material system combining dibenzofuran core structure with specific substituents (A and B groups) to achieve the desired triplet energy level. This composite molecular structure integrates multiple functional components: the dibenzofuran core provides the base structure, while the substituents tune the energy levels and stabilize the triplet state, resulting in a host material that simultaneously achieves high triplet energy and manufacturability.
2Use of energy by moving object
If phosphorescence material is used in the light emitting layer, then more excitons can be converted to light, but reverse energy transition occurs when the host triplet energy level is lower than the dopant triplet energy level
Solution Approach 1:
The patent raises the triplet energy level parameter of the host material to above 2.9 eV, which is higher than the triplet energy level of the phosphorescence dopant (Flrpic at 2.9 eV). This parameter adjustment eliminates the thermodynamic driving force for reverse energy transition, allowing complete unidirectional energy transfer from host to dopant and maximizing exciton utilization efficiency.
Solution Approach 2:
The patent prevents reverse energy transition by designing the host material with sufficiently high triplet energy level before the device operates. This preliminary design choice creates an energy level configuration that inherently prevents the harmful reverse transition process, ensuring that all excitons generated in the host material are transferred forward to the phosphorescence dopant without loss.
3Productivity
If high triplet energy host material is used, then reverse energy transition is prevented and efficiency is improved, but the molecular structure becomes more complex
Solution Approach 1:
The patent employs a composite molecular structure consisting of a dibenzofuran core with systematically designed substituents. This composite approach achieves high triplet energy (>2.9 eV) through the synergistic combination of the core structure and substituents, rather than requiring entirely complex molecular architectures. The modular composite design balances structural complexity with performance requirements.
Solution Approach 2:
The patent applies local quality by introducing specific substituents (A and B groups) at particular positions on the dibenzofuran core. These localized structural modifications at specific positions (Nos. 2 and 7 or Nos. 3 and 6) are sufficient to tune the triplet energy level to the required range, avoiding the need for complete molecular redesign and reducing overall structural complexity while maintaining high emission efficiency.
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 improves the emission efficiency and life span of OLEDs while maintaining color coordinates, as demonstrated by the increased quantum efficiency and extended life span of the devices using the new host material compared to traditional materials.
Implementation Method 1
an energy level of singlet excitons generated in the host is transferred to a singlet energy level or a triplet energy level of a dopant, and an energy level of triplet excitons generated in the host is transferred to the triplet energy level of the dopant
Implementation Method 2
A blue phosphorescence compound with high triplet energy is used as the host material in the light emitting layer
Implementation Method 3
When triplet energy levels of the hole transport layer and the electron transport layer positioned in the front or in the rear of the light emitting layer are less than the triplet energy level of the dopant, a reverse energy transition from the dopant or the host to the hole transport layer and the electron transport layer is generated
Data Source
AI summary
A blue phosphorescence compound and an organic light emitting diode using the same are disclosed. The blue phosphorescence compound is represented by Chemical Formula 1 below:wherein ‘A’ and ‘B’ are symmetrically or asymmetrically substituted at positions of Nos. 2 and 7 or Nos. 3 and 6 of dibenzofuran core and are independently formed of an aromatic cyclic compound or a heterocyclic compound.