Star-Shaped Sulfone Compound for OLED Electron Mobility
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Solution Overview
Problem
Conventional OLED devices face inefficiencies and reduced lifetimes due to the significant disparity in hole and electron mobility, leading to unbalanced current combinations near the cathode, which quenches excitons and decreases efficiency and lifetime.
Innovation Solution
A sulfone group-containing compound with a star-shaped molecular structure, formed by connecting multiple fluorene sulfur oxide units with a bridging unit, is used in the light emitting or electron transport layer to enhance electron mobility and affinity, promoting balanced hole and electron current combinations throughout the light emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electron-transporting materials are used, then the device structure is simple, but the electron mobility is low (10^-5 to 10^-6 cm²V^-1s^-1) causing unbalanced current distribution
Solution Approach 1:
The patent uses composite molecular structure combining fluorene units with sulfone groups to create electron-transporting materials with high electron mobility. The compound integrates electron-rich fluorene cores with electron-withdrawing sulfone groups, achieving balanced electron transport capability while maintaining structural organization
Solution Approach 2:
The patent modifies molecular parameters by introducing sulfone groups at specific positions (C-9) of fluorene units, changing the electron affinity and HOMO/LUMO energy levels. This parameter optimization enables higher electron mobility (exceeding 10^-4 cm²V^-1s^-1) and improved electron injection efficiency
2Reliability
If conventional hole-transporting materials are used, then the hole mobility is high (10^-2 to 10^-3 cm²V^-1s^-1), but the electron mobility remains low causing un-equilibrium of currents
Solution Approach 1:
The patent applies local quality modification by placing sulfone groups at specific positions (C-9) of the fluorene units. This localized electron-withdrawing group creates regions of high electron affinity that facilitate electron injection and transport while maintaining overall molecular stability and structural integrity
Solution Approach 2:
The patent optimizes energy level parameters by adjusting the electron affinity and HOMO/LUMO gaps through sulfone group introduction. This enables the material to achieve both high electron mobility and appropriate energy level alignment with adjacent layers, ensuring balanced current distribution
3Productivity
If the combination zone of holes and electrons is formed nearby cathode, then the device structure is simple, but the excess hole-concentration current quenches excitons decreasing efficiency
Solution Approach 1:
The patent optimizes the LUMO energy level parameter to achieve appropriate offset with the electron transport layer, enabling controlled electron injection. This energy level tuning ensures that electrons are injected at optimal rates, preventing excessive electron accumulation that would lead to exciton quenching while maintaining high luminescence efficiency
Solution Approach 2:
The patent implements feedback control through balanced electron and hole transport capabilities. The material's dual functionality allows it to respond to local charge distribution conditions, automatically regulating current flow to maintain equilibrium between hole-concentration and electron-concentration currents throughout the light emitting layer
4Adaptability or versatility
If most available phosphorescence materials are used, then they are easy to obtain, but they are not dipole materials lacking both high hole and electron mobility
Solution Approach 1:
The patent creates composite molecular structures integrating fluorene units with sulfone groups, achieving dual functionality for both hole and electron transport. This composite design enables the material to act as a dipole material with balanced mobility characteristics, suitable for use as host material in phosphorescence OLEDs
Solution Approach 2:
The patent achieves multi-functionality by designing compounds that simultaneously provide hole transport, electron transport, and host material capabilities. The fluorene-sulfone compounds can serve multiple roles in the OLED structure, reducing the need for separate functional layers and simplifying device architecture
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 sulfone group-containing compound improves the efficiency and lifetime of OLED devices by ensuring balanced current combinations and forming a stable amorphous film, thereby increasing electron-injecting and transporting abilities.
Implementation Method 1
The sulfone group is an electron-withdrawing group, and has higher electron affinity and an energy band gap of approximately 2.8 eV; therefore, the fluorene sulfur oxide can easily conduct electrons for injection and transport
Implementation Method 2
S atom in the sulfone group is at the highest valence state, so as the sulfone group can be a stronger antioxidant, thus the fluorene sulfur oxide has a strong thermal stability
Implementation Method 3
Due to star-shaped molecule structure, a compound of a star-shaped molecule structure has characteristics such as great molecular weight, large steric, high glass-transition temperature, poor crystallinity and easily forming a stable amorphous film
Implementation Method 4
the excitons radiate luminescence due to attenuation from excited state to bound state of exciting electrons of the excitons
Data Source
AI summary
The present invention provides a sulfone group-containing compound, an organic light emitting diode (OLED) device using the sulfone group-containing compound, and a method of fabricating the OLED device. The sulfone group-containing compound has formula aswherein the bridging unit R is capable of connecting to three or more than three fluorene sulfur oxide units; and the unit R1, R2 and R3 respectively connected to the fluorene sulfur oxide units are selected from alkyl chains, aromatic groups or heterocyclic groups. According to the present invention, the sulfone group-containing compound connects to three or more than three fluorene sulfur oxide units with a bridging unit to form a novel star-shaped molecular structure. The sulfone groups-containing compound combines electron affinity and transport properties of the fluorene sulfur oxide units and spatial characteristics of the star-shaped molecular structure, so that efficiency and lifetime of an OLED device using the same can be enhanced.