OLED Emitting Layer Energy-Level Design for Color Purity and Lifetime
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional OLEDs using blue phosphorescent materials suffer from low color purity and unsatisfactory lifetime, limiting their application in commercial display devices, while those using fluorescent materials have limited luminous efficiency due to the inefficiency in utilizing both singlet and triplet excitons.
Innovation Solution
An OLED design incorporating a first emitting material layer with a first and second delayed fluorescent material, where the excited triplet energy levels and lowest unoccupied molecular orbital energy levels satisfy specific relationships, and utilizing organic compounds with defined structures, enhances luminous efficiency and lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If blue phosphorescent material is used in OLED, then luminous efficiency is enhanced by utilizing both singlet and triplet excitons, but color purity becomes too low and lifetime becomes unsatisfactory
Solution Approach 1:
The patent changes the energy level parameters of the emitting materials by selecting specific delayed fluorescent materials with carefully controlled triplet energy levels (T1DF1 and T1DF2) that satisfy specific relationships (T1DF2 > T1DF1 and both less than T1H). This parameter optimization enables efficient triplet exciton utilization while maintaining high color purity and extended lifetime, resolving the contradiction between luminous efficiency and device reliability
Solution Approach 2:
The patent employs a composite emitting material layer containing multiple delayed fluorescent materials (first delayed fluorescent material with triplet energy level T1DF1 and second delayed fluorescent material with triplet energy level T1DF2) combined with a host material. This composite structure enables synergistic utilization of both singlet and triplet excitons through delayed fluorescence mechanisms, achieving high luminous efficiency while maintaining color purity and lifetime through the coordinated energy level design of the composite system
2Reliability
If conventional fluorescent material is used in OLED, then color purity is maintained, but luminous efficiency is limited to about 5% due to inability to utilize triplet excitons
Solution Approach 1:
The patent fundamentally changes the luminescence mechanism parameter by transitioning from conventional fluorescent emission to delayed fluorescent emission. By selecting delayed fluorescent materials with specific triplet energy levels that are lower than the host's triplet energy level (T1DF1 < T1H and T1DF2 < T1H) but maintain appropriate relationships, the system can now utilize triplet excitons through thermally activated delayed fluorescence, breaking the 5% efficiency limit while preserving color purity through controlled energy level parameters
Solution Approach 2:
The patent implements continuous useful action by enabling the system to continuously convert both singlet and triplet excitons into light emission through the delayed fluorescence mechanism. The triplet excitons that would normally be lost are continuously converted to singlet excitons via thermal energy, which then emit light, creating a continuous cycle of useful light production that eliminates the 75% energy loss inherent in conventional fluorescent materials
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 improved luminous efficiency and lifetime, along with enhanced color purity, by effectively utilizing both singlet and triplet excitons through delayed fluorescent materials, overcoming limitations of conventional fluorescent and phosphorescent materials.
Implementation Method 1
the first emitting material layer comprises a first host, a first delayed fluorescent material and a second delayed fluorescent material
Implementation Method 2
the singlet exciton can be converted to the triplet exciton via intersystem crossing (ISC)
Implementation Method 3
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 combined to be paired, and then emit light as the combined electrical charges are disappeared
Data Source
AI summary
The present disclosure relates to an organic light emitting diode and an organic light emitting device having the diode. An organic light emitting diode including a plurality of delayed fluorescent materials with specific energy levels and an organic light emitting device including the diode is disclosed. When the plurality of delayed fluorescent materials with specific energy levels are applied in an emitting material layer, it is possible to minimize the energy loss or exciton quenching during luminescent process, to prevent the diode from reducing lifetime caused by the exciton quenching, and to make charges being injected into the emitting material layer in balance. When the emitting material layer includes other luminous material having a narrow FWHM, the organic light emitting diode can enhance its color purity.