Design,Synthesis And Properties Of Aromatic-Ketone-Based Thermally Activated Delayed Fluoresecent Material

The thermally activated dalayed fluorescence(TADF)material has been considered as the third-generation organic light-emitting device(OLED)emitter,a theoretic maximum exciton utilization of 100%can be realized since triplets can be harvested as delayed fluorescence through their up-conversion from a lowest triplet state to a lowest singlet state by inducing efficient reverse intersystem crossing,which becomes the first choice for the fabrication of high performance devices in theory.In recent years,new high performance TADF materials has become a research focus,and the design of new groups and molecular structures to improve the performance of TADF materials has been the goal of researchers.In this paper,we designed a series of TADF materials based on anthrone as the acceptor group.The main research work is as follows:(1)A novel yellow TADF compound(4-(10H-phenoxazin-10-yl)phenyl)(anthracen-9-yl)methanone(AnMPXZ)was designed and synthesized using anthrone as electron acceptor and phenoxazine as electron donor.The molecular orbital calculation shows that the highest occupied molecular orbital(HOMO)and lowest unoccupied orbital(LUMO)of the molecule were mainly distributed on the phenoxazine donor group and the anthrone acceptor group,and only some overlapped on the benzene ring.Thermodynamic study shows that AnMPXZ has better thermal stabilities with the decomposition temperatures of 358°C.Photophysical tests show that its singlet-triplet energy gap was 0.18 eV.An organic light-emitting device using AnMPXZ as doping object light-emitting layer displayed emission peak at around 554 nm with CIE coordinates of(0.45,0.53),which maximum luminance,maximum current efficiency,power efficiency and external quantum efficiency were 23900 cd/m~2,37.0 cd/A,33.3 lm/W,11.9%,respectively.The efficiency roll-off is very small with the increase of brightness.(2)A series of white light TADF molecules(4-(9H-carbazol-9-yl)phenyl)(anthracen-9-yl)methanone(AnMCz),anthracen-9-yl(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)methanone(AnMtCz)and anthracen-9-yl(4-(diphenylamino)phenyl)methanone(AnM-DPA)were synthesized using anthrone as electron acceptor,carbazole,tert butyl carbazole and diphenylamine as electron donor.Compounds:AnMCz,AnMtCz and AnMDPA have very small singlet-triplet energy gap of 0.11 eV,0.05 eV and 0.08 eV,respectively.Fluorescence spectrum has the dual emission properties of blue and yellow,and the blue light comes from the localized anthracene group,while the yellow light comes from the intramolecular donor-acceptor charge transfer state.The warm white organic light-emitting devices using these materials as doping object light-emitting layer covered the whole visible light range from 400 to 700 nm.Especially,the AnMtCz-based device achieved a maximum external quantum efficiency of 3.37%with CIE coordinates of(0.40,0.35).These results show that by selecting the appropriate donor and acceptor unit,we can design the white light material with TADF characteristics and fabricate the high efficiency single molecule light-emitting layer WOLED.In summary,novel yellow and monomolecular white light TADF materials were synthesized by using aromatic ketone as electron acceptor and different electron donor groups,which providing a reference for the design of TADF molecular and the study of single molecular white light materials.