Synthesis And Properties Of Phosphorescnet Host Materials And Thermally Activated Delayed Fluorescence Materials

Since the development of organic light-emitting diodes?OLEDs?,phosphorescence and thermally activated delayed fluorescence devices have attracted much attention due to their theoretical ability to make the most of exciton luminescence.Therefore,in this thesis,we have designed and synthesized one phosphorescence host material and four thermally activated delayed fluorescence materials,all of which are D-A type organic small molecular luminescent materials based on sulfone group.In the first system,we synthesized the compound 2-?10H-phenoxazinyl?thionazol-9-one-10,10-dioxide?TXOPXZ?by using the phenoxazine?PXZ?as the electron acceptor unit?A?.The UV absorption peak was measured at 232 and285 nm in 10^-55 mol L^-11 DCM dilute solution,and its optical band gap?Eg?was 3.33eV.At room temperature,the fluorescence emission peak in DCM diluted solution was measured at 443 nm,which belongs to dark blue fluorescence,and the fluorescence quantum yield was 25.5%.At 77 K,the first phosphorescent emission peak was measured at 460 nm,and the triplet level?E_T?was calculated to be 2.70eV,which was larger than that of the guest material FIrpic?2.62 eV?.Through the CV curve of TXOPXZ,we calculated its HOMO energy level as-5.28 eV,matched with the work function of ITO?-4.5^-5.0 eV?,the LUMO energy level was-1.95eV,matched with TAZ?-2.30 eV?of common electron input material,which showed well bipolar transmission performance.The decomposition temperature?T_d?was 327?,and the DSC chart analysis showed that the TXOPXZ had a high glass transition temperature?T_g?of 191?.It shows that it has amorphous form,film-forming property and film stability.Therefore,it can be seen that the TXOPXZ has excellent heat stability,and was a blue phosphorescent host material with good bipolar transmission performance.In the second system,diphenyl sulfone was used as the electron acceptor unit?A?,and phenoxazine and acridine were used as electron donor units?D?to connect to the ipsilateral side of diphenyl sulfone.We designed and synthesized two kinds of TADF materials:10,10'-?5-?benzenesulfonyl?-1,3-benzal?bis?9,9-dimethyl-10-Phenoxazine??2PXZDPS?and 10,10'-?5-?benzenesulfonyl?-1,3-benzal?bis?9,9-dimethyl-9,10-Dihydroacridine??2DMACDPS?.In 10^-5mol L^-1DCM dilute solution,The UV absorption peak of 2PXZDPS was measured at 238 and 317 nm,The UV absorption peak of 2DMACDPS was measured at 228,280 and 364 nm,and their optical band gap?Eg?was 2.99 and 3.07 eV,respectively;At room temperature,in the DCM dilute solution of 2PXZDPS and 2DMACDPS,the fluorescence emission peaks measured with the excitation wavelength of 360 nm are located at 590 and 531 nm,respectively,which belong to yellow light and green light,respectively.The calculated fluorescence quantum yields???were 53.5%and 77.6%,respectively.The fluorescence quantum yields increased by 6.6%and 8.2%after oxygen removal,respectively,which indicated that both 2PXZDPS and 2DMACDPS had delayed fluorescence phenomenon,and from their transient spectra,it was found that both compounds exhibited double exponential decay,representing transient fluorescence and delayed fluorescence processes.It is proved that both products have delayed fluorescence phenomenon,and the delayed fluorescence lifetime of2PXZDPS and 2DMACDPS were 0.21 and 0.40?s,respectively.Through the CV curves,we calculated the HOMO energy level of 2PXZDPS and 2DMACDPS were-5.28 and-5.16 eV,respectively,and the LUMO energy level were-2.29 and-2.09 eV;From the TGA curves,The decomposition temperature?T_d?of 2PXZDPS and2DMACDPS were 408 and 388?,respectively,which show excellent thermal stability.;To sum up,both 2PXZDPS and 2DMACDPS are expected to produce good luminescent devices.In the third system,we designed a novel receptor unit with pyridine ring and linked two excellent donor units phenoxazine and carbazole.Two kinds of TADF materials,4-?pyridine-3-sulfonyl?phenyl-10-phenoxazine?BDPXZ?and4-?pyridine-3-sulfonyl?phenyl-9-carbazolium?BDCZ?,were obtained.With the excitation wavelength of 500 nm,BDPXZ has a fluorescence emission peak at 579nm,which belongs to yellow-green fluorescence emission,and BDCZ has a fluorescence emission peak at 446nm,which belongs to sky blue fluorescence emission.The fluorescence quantum yields of the two compounds were calculated to be 38.6%and 72.8%,respectively,and the fluorescence quantum yields of BDCZ increased by 12.7%after oxygen removal,which indicated that compound BDCZ probably had delayed fluorescence phenomenon.It was found that the two compounds exhibit double exponential decay from their transient spectra,which are transient fluorescence and delayed fluorescence,respectively.It is proved that both products have delayed fluorescence emission.The delayed fluorescence lifetime of BDPXZ and BDCZ were 0.13 and 0.33?s,respectively;Through the CV curves,We calculated the HOMO energy level of BDPXZ and BDCZ were 5.21 and 5.18 eV,respectively,the LUMO energy level were 2.28 and 2.07 eV,respectively;From the TGA datagram,the decomposition temperatures of BDPXZ and BDCZ were 272 and338?,respectively,which showed excellent thermal stability.In conclusion,the combination of pyridine sulfone group can be used as an excellent receptor material in the design of TADF materials.