Design,Synthesis And Properties Of Luminescent Materials Based On Sulfonyldibenzene Group

After the development of traditional fluorescent materials and phosphorescent materials,organic electroluminescent materials have exceeded 25%of singlet exci-tons and achieved theoretical 100%internal quantum efficiency.In recent years,thermally activated delayed fluorescence?TADF?materials with donor-acceptor?D-A?framework,regarding as the third generation of organic electroluminescent materials,have been attracted much attention by researchers due to the free of metal atom and their ability for harvesting both singlet and triplet excitions.Diphenyl sulfone unit has weak electron-withdrawing properties,ease modifica-tion and twist structure,which is usually used as the fragments in blue TADF mole-cules.However,little diphenyl sulfone-based TADF and phosphorescent materials bearing dual emissions have been reported.To this end,in this thesis,a series of di-phenyl sulfone based novel emissive materials were designed and synthesized to fur-ther explore the intramolecular energy transfer.¹H NMR,¹³C NMR,MALDI-TOF mass were carried out to confirm the molecular structures.The frontier molecular or-bital density distribution of these molecules was calculated via density functional the-ory.Their photophysical properties were systematically investigated by steady-transient fluorescence spectrometer,cyclic voltammetry?CV?and thermo-gravimetic analysis?TGA?.Using these novel emissive materials as the emitter,or-ganic light-emitting diodes were?OLEDs?fabricated via solution processable.Then the relationship between the molecular structure and device performance was further explored.The main research contents of the thesis are as follows:?1?Employing the carbazole-diphenyl sulfone as a blue emissive fragment and the triphenylamine-anthraquinone as a red emissive moiety,a series of novel TADF mate-rials bearing two chromophores were constructed via non-conjugated oxygen at-om/alkoxy chain.All these TADF materials possessed good thermal stablility with a decomposed temperature of>350?at 5%weight loss.Dual emissions both at short wavelength and long wavelength were detected in solution for these TADF materials,implying that introduction of the non-conjugated linker into molecule plays a key role on suppressing the intramolecular energy transfer.Long lifetime in the range of mi-crosecond were demonstrated by transient fluorescence spectrometer,which suggests that these molecules could have TADF characters.Using these dual emissive materi-als as the emitter,the solution processable OLEDs achieved a maximum external quantum efficiency?EQE?of 3.74%.?2?Two platinum complexes,named?2Fppy-DPS-Cz?Pt?acac?and?2Fppy-O-DPS-Cz?Pt?acac?,containing the TADF moiety of carbazole-diphenyl sul-fone and cyclometalating ligand of 2,4-difluorophenylpyridine were designed and prepared.The structures of both platinum complexes were confirmed by NMR,MS and single crystal X-ray diffraction.Both platinum complexes showed strong emis-sion in toluene.Their thermal statbilities,electrochemical properties and photophysi-cal properties were studied via TGA,CV and photoluminescence.Notably,complex?2Fppy-O-DPS-Cz?Pt?acac?exhibited a blue shifed emission?ca.36 nm?than that of?2Fppy-DPS-Cz?Pt?acac?in solution,which is attributed to the oxygen atom in com-plex?2Fppy-O-DPS-Cz?Pt?acac?destroyed the conjugation degree.The solution pro-cessable OLEDs employing both platinum complexes as the emitter presented the EQE of 7.57%and 7.10%for?2Fppy-DPS-Cz?Pt?acac?and?2Fppy-O-DPS-Cz?Pt?acac?,respectively.