OLED Intermediate Layer LUMO Energy Level Optimization
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Solution Overview
Problem
Current organic light emitting diodes (OLEDs) face limitations in display performance due to the inefficiency of fluorescent materials, which only utilize singlet excitons for emission, restricting their emitting efficiency.
Innovation Solution
The OLED structure includes a first emitting material layer with specific compounds and an intermediate functional layer having a higher lowest unoccupied molecular orbital (LUMO) energy level, enhancing the LUMO energy level in the intermediate layer to improve charge balance and prevent exciton transfer, thereby increasing emitting efficiency and reducing driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluorescent material is used as emitter in OLED, then the device can be manufactured with current technology, but the emitting efficiency is limited because only singlet exciton is involved in emission
Solution Approach 1:
An intermediate functional layer is introduced between the emitting material layer and the hole blocking layer. This intermediate layer acts as a mediator to improve charge balance and prevent exciton transfer to the hole blocking layer, thereby enhancing emitting efficiency while maintaining compatibility with existing manufacturing processes
Solution Approach 2:
The LUMO energy level of the intermediate functional layer is specifically designed to be higher than that of the emitting material layer. This parameter change in energy level configuration improves charge balance and prevents exciton transfer, resolving the efficiency limitation while preserving manufacturability
2Device complexity
If conventional OLED structure is used, then the device structure is simple, but the charge balance is poor and exciton transfer occurs reducing emitting efficiency
Solution Approach 1:
The OLED structure is segmented into distinct functional layers: emitting material layer, intermediate functional layer, and hole blocking layer. This segmentation allows each layer to perform its specific function optimally, improving charge balance and preventing exciton transfer while maintaining reasonable structural complexity
Solution Approach 2:
The intermediate functional layer serves as a mediator between the emitting material layer and the hole blocking layer, improving charge balance and preventing direct exciton transfer to the hole blocking layer, thereby enhancing emitting efficiency without excessive structural complexity
3Loss of energy
If the LUMO energy level of intermediate layer is increased, then charge balance is improved and exciton transfer is prevented, but the device complexity increases
Solution Approach 1:
The LUMO energy level of the intermediate functional layer is optimized to be higher than that of the emitting material layer. This specific parameter change improves charge balance and prevents exciton transfer, achieving better emitting efficiency while managing the complexity of energy level configuration
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 enhances the emitting efficiency and luminance of the OLED by improving charge balance and shifting the exciton generation zone, leading to improved display performance and reduced full width at half maximum (FWHM).
Implementation Method 1
The OLED emits light by injecting electrons from a cathode as an electron injection electrode and holes from an anode as a hole injection electrode into an emitting material layer, combining the electrons with the holes, generating an exciton, and transforming the exciton from an excited state to a ground state
Data Source
AI summary
An organic light emitting diode can include a first electrode, a second electrode facing the first electrode, and a first emitting part including a first emitting material layer between the first and second electrodes, a first hole blocking layer between the second electrode and the first emitting material layer and a first intermediate functional layer between the first emitting material layer and the first hole blocking layer. The first emitting material layer includes a first compound, a second compound and a third compound. The first intermediate functional layer includes a first compound and a second compound. The second compound in the first intermediate functional layer has a core that is the same as the second compound in the first emitting material layer and has a higher LUMO energy level than the second compound in the first emitting material layer.