Design, Synthesis And Electroluminescence Properties Of Solution-processable Dianthracene-based Blue Organic Delayed Fluorescent Materials

The level of science and technology is advancing speed.In terms of display technology,organic light-emitting diodes(OLEDs)are favored by a large number of scientific researchers due to their self-luminous,low lighting voltage,flexibility.The blue materials light-emitting is indispensable as a full-color display and energy-saving lighting in OLED applications.At present,OLED commercialize mainly adopt vacuum evaporation.In order to reduce costs,bule molecules that solution-processable are the focus of research.However,most of the traditional solution-processed molecules are polymers,and the low reproducibility of polymers has become a bottleneck restricting the development of solution-processed OLEDs.Therefore,the exploit of solution-processable small molecules is of great significance.The main content of this paper is as follows:The thesis has five parts.Chapters 2,3,and 4 mainly introduce the main work of the master's three years,Designed and synthesis a series of solution-processable bisanthracene molecules,from linear phenyl bridges ?-conjugated to curved phenyl bridges ?-conjugated,and finally hyperconjugated ? bridged bisanthracenes.derivative.And test the thermal,photophysical and electrochemical properties of these molecules,after analyze the values.Although all molecules can realize solution-processable devices these doped and nodoped,it is necessary to optimize the device to further improve the performance of the devices.The first chapter introduces the development process from the discovery of organic light-emitting diodes to commercial applications,and then explains the luminescence mechanism,device structure,device performance parameters,classification of organic optoelectronic materials,solution-processed the advantages of compared to traditional vacuum evaporation and the method of device fabrication.Finally,briefly explain the selection topic meaning and ideas of this article.In the second chapter,with the anthracene chromophore as the core,based on the BD dianthracene blue light-emitting molecule synthesis by Hu et al.in 2014,a series of blue chromophores with solution processability are synthesis.Two compounds BD1-BB and BD3-BCN were synthesized by a simple Suzuki reaction.The research the thermal results show that they all have high thermal stability(Tg>350?)and exhibit blue light emission(wavelength 427-442 nm)in optical behavior.The HOMO and LUMO energy levels tested by cyclic voltammetry are consistent with theoretical calculations,and the numerical values show that it is beneficial to the injection and transport of electrons and holes.The theoretical calculation of the optimized molecular structure show that the introduction of alkyl chains can also increase the dihedral angle(? 90°)of molecular twist and inhibit the ?-? stacking of molecules in the film state.When the BD3-BCN molecule is used as a guest material,the turn-on voltages is 3.2 V,and the maximum EQE is 1.86%.In the third chapter,we synthesized two curved mBDl-BB and mBD3-BCN molecules through molecular engineering to further limit the ?-conjugation of the molecules.The two molecules also have a higher thermal decomposition temperature.The DFT theoretical calculation results show that our assumption is correct.The two molecules are more distorted in the three-dimensional space,and the dihedral angle between the two anthracene groups and the adjacent benzene ring has indeed increased(>90°).A clear blue shift was also observed in the photoluminescence spectrum(?PL=414 nm).For doped devices based on solution-processed mBD3-BB molecules,the CIE coordinates of the EL spectrum are(0.15,0.06),and the FWHM=58 nm,which is consistent with the HDTV standard blue CIE(0.15,0.06).The fourth chapter,the previous deep blue materials basically use a fully conjugated benzene ring as a bridge to connect the two light-emitting units.Because the adjacent C atom orbitals on the benzene ring are all hybridized with Sp2,it cannot effectively inhibit the molecules.According to the inspiration of Donor-?-Acceptor type molecule reported by Mr.C.Adachi,the BD1-CF3-BB and BD3-CF3-BCN molecule was synthesized by connecting two anthracene luminophores on a hyperconjugated ?bridge chain.The C atom orbital of the hyperconjugated a bridge chain adopts Sp3 hybridization,which is a regular tetrahedral structure in space,which can more effectively limit the conjugated form and excited state charge transfer path of organic molecules.At the same time,the introduction of steric hindrance groups at both ends of the central hyperconjugated ? bridge chain further inhibits the ?-? stacking effect between organic molecules,and the prepared dark blue organic fluorescent material has good thermal stability(Tg>380?)and high luminous quantum efficiency(PLQY=91%).The EQE of the BD3-CF3-BCN molecular device based on vacuum evaporation is 5.11%.The fifth chapter briefly summarizes the research of this paper,and puts forward some opinions and opinions for the large-scale commercialization of OLED in the future.