Synthesis And Characterization Of Alcohol Soluble Host Materials And Thermally Cross-linking Hole-Transport Materials For Solution-Processed Electrophosphorescent Devices

In recent years, organic light emitting diodes(OLEDs) as a new generation of technology has received the widespread attention around the world. OLEDs has a wide color gamut, high contrast, low energy consumption which conforms to the developing direction of future display, can be used in the manufacture of flexible display and wearable equipment. At present, many international big companies are committed to the research of OLEDs devices, OLEDs is mainly suitable for the television, mobile phone screen.The OLEDs device is mainly manufactured by vacuum evaporation method which cost is much higher and also not conducive to large-scale production. In comparison, the method such as spin coating which belongs to solution processing can reduce the production cost and put into production of large area because its manufacturing environment requirements is not as demanding as vacuum evaporation. Therefore, the solution processed OLEDs is what we should focus on research. But so far, the solution processed OLEDs devices common problem is the low device efficiency and vulnerable to the interference of the surroundings.The main research work can be summarized as following:(1) Two novel alcohol soluble bipolar host materials 9PhCz-BPO and 3PhCz-BPO with high triplet energy were designed and synthesized. The introduction of polar diphenylphosphine oxide (PO) units in molecular structures can enhance their solubility in alcohol solvents. The alcohol soluble feature of the host enable the insertion of high triplet energy hole-transport layer between PEDOT:PSS and emitting layer to protect the triplet excitons. Furthermore, the PO unit also possesses a high triplet energy (>3.0 eV) and excellent electron-transport property. The thermal stability, electrochemical and photophysical properties and EL performance of these host materials are fully investigated.(2) Soluble host materials DV-CDBP was designed and synthesized. Based on traditional hole-transporting molecular 4,4’-double (N-carbazole)-1,1’-biphenyl (CBP), we redesigned the molecular structure of the CBP, completed the synthesis of molecular and further optimize the performance of the CBP molecules, making it can be used for solution processing of OLEDs. Both DFT calculation and experiment results demonstrate that due to the enhanced molecular rigidity, the triplet energy of DV-CDBP reaches 2.95 eV. With structural topology modification, the particular physical properties of the materials can be subtly optimized, such as the thermal stability, singlet-triplet energy gap and charge balance ability. This study demonstrated that molecular modulation was an effective way to develop efficient hole-transport materials.