| As a kind of cyclic organic compounds with excellent thermoelectric chemical stability,Organic Nano Grid-Aromatics are an effective way to improve the performance of Thermally Activated Delayed Fluorescence materials.Firstly,by introducing functional groups such as arylfluorene,carbazole,and spirofluorene,it has the characteristic of multiple steric hindrance,which can effectively reduce intramolecular rotation and suppress intermolecular interactions;Secondly,Gridarene have numerous chemical reaction sites and can be constructed into various cyclic structures through molecular design and different reaction modes,such as Angular Grid,Mouth-shape Grid,Rhombic Grid,heliograms Grid,and A-shaped Grid;Finally,the Gridarene usually has a large molecular weight,which helps to align the molecules after film formation,so that it has a high Transition dipole moment,thereby improving the luminous efficiency of the device.Organic boron acceptors have advantages such as structural stability,ability to exhibit deep blue light emission,good color purity,and narrow FWHM,and are often used as receptors for D-A type TADF materials.At present,there are few reports on circular TADF materials both domestically and internationally.In this paper,a series of A-shaped Grid TADF materials based on fully bridged boron-type acceptor and with blue/green light emission were synthesized through efficient one-pot Friedel-Crafts reaction,and their undoped solution processing OLED devices were prepared,effectively improving the device performance and luminescence efficiency of TADF small molecule after cyclization.Firstly,D-A type small molecule DMAC-TDBA was synthesized by Buchwald-Hartwig coupling reaction,and small molecule DMAC-TDBA was modified by using arylfluorene functionalization and Gridization strategy.Two kinds of D-A type blue thermally activated delayed fluorescent materials DPFDMAC-TDBA and A-shaped Grid ACAG-TDBA were obtained respectively.It was found that the modified two materials had excellent thermoelectric chemical stability and good film forming properties.By systematically studying the UV-PL spectra of the three,it was found that they all have significant ICT effects,which are conducive to achieving the emission of TADF,and their FWHM is around 50 nm.We also prepared non doped devices of the three through solution processing,with DPFDMAC-TDBA having a maximum brightness of 6500cd m-2 and an external quantum efficiency of 9.05%.Secondly,by changing the strategy of electron-donating groups and effective conjugation length,small molecule PXZ-TDBA was synthesized first.Similarly,three Thermally Activated Delayed Fluorescence materials with blue green/green light emission were successfully synthesized through a simple and efficient Friedel-Crafts reaction,namely DPFPXZ-TDBA modified with aryl fluorene and two A-shape Grid PXZAG-TDBA and m-PXZAG-TDBA.Through further research,it was observed that they all had excellent thermal stability,electrochemical stability and film forming property.By comparing the arylfluorene modified DPFPXZ-TDBA with the A-shaped Grid material m-PXZAG-TDBA,we found that m-PXZAG-TDBA had a higher photoluminescence quantum yield（90.42%）and exhibited blue-green light emission.By preparing their undoped solution processing devices,it was observed that the maximum brightness of A-shaped Grid m-PXZAG-TDBA was 6600 cd m-2,and the maximum external quantum efficiency reached 9.66%.Therefore,it has been proven that the Gridization strategy is an effective way to improve the performance of TADF materials.Finally,in Chapter 4,when synthesising the A-shaped Grid material m-PXZAG-TDBA,we synthesized containing A-shaped Grid and long linear material m-LPXZ-TDBA and Binary-Grid m-DPXZAG-TDBA simultaneously using a one-pot strategy by controlling reaction conditions.We successfully separated these three compounds through column chromatography.Through later tests,it is found that all three have excellent thermoelectric chemical stability.By comparing their photophysical properties,it is found that A-Grid and binary-Grid have higher photoluminescence quantum yield（90.42%,92.10%）than long linear materials.By preparing undoped solution processing devices of the three,it was observed that they all exhibit excellent device performance,exhibiting blue-green/green light emission,with a threshold voltage of around 4 V.The maximum external quantum efficiency of A-shaped Grid m-PXZAG-TDBA and Binary-Grid m-DPXZAG-TDBA reached 9.66%and 9.89%,respectively. |
