Synthesis And Characterization Of Solution Processed Hyper-structured Thermally Activated Delayed Fluorescence Materials-Thioxanthone Based On Derivatives

Thermally activated delayed fluorescence?TADF?materials are capable of efficient reverse intersystem crossing?RISC?from the triplet excited state?T₁?to the singlet excited state?S₁?to use triplet excitons for photoluminescence with theoretically 100%exciton harvesting in emission.Hyper-sructured TADF molecules were the molecules with asymmetrical complex structure that binds the desired functional groups to a three-dimensional core body.In this paper,we first designed and synthesized two kinds of azide-containing functional compounds TXO-PhCz-O-N₃ and TXO-TPA-O-N₃ with delayed fluorescent effect,and a host component mCP-O-N₃ with hole transporting ability.Then,the azide-alkyne"click chemistry"reaction was performed between azide-containing functional coumpounds and alkyne-containing calix4-resorcinarene?CRA?derivative CRA-Alkyne to obtain four hyper-sructured TADF materials CRA-TXO-PhCz _X-mCP_?100-X??X=100,50,12.5?and CRA-TXO-TPA₁₀₀.The chemical structures and properties of objective coumpounds and intermediates were characterized by proton nuclear magnetic resonance?¹H NMR?,fourier transform infrared spectra?FT-IR?,elemental analyzer?EA?,high-resolution mass spectrum?HR MS?,matrix-assisted laser desorption ionization time-of-fight mass spectrum?MALDI-TOF MS?,X-ray diffraction analysis?XRD?,thermogravimetric analysis?TGA?,differential scanning calorimeter?DSC?,UV-Visibleabsorption spectrum?UV-Vis?,photoluminescence spectrum?PL?,cyclic voltammetry,etc.Spin-coating as-parepared materials doped into mCP as the emitting layer?EML?,OLED were fabricated and measured.Part one,model luminescent molecule TXO-PhCz,azide-containing functional compound TXO-PhCz-O-N3 and the hyper-structured TADF materials CRA-TXO-PhCz_X-mCP_?100-X??X=100,50,12.5?were synthesized and characterized.First,the functional compounds TXO-PhCz-O-N₃ and mCP-O-N₃with azide groups as the end group,and CRA derivative?CRA-Alkyne?with eight alkynyl groups as the end groups were synthesized.Then,through"click chemisty"reaction,TXO-PhCz-O-N₃ and mCP-O-N₃ with different molar ratios were reacted with CRA-Alkyne to form different hyper-structured TADF molecules CRA-TXO-PhCz_X-mCP_?100-X??X=100,50,12.5?,which has a triazole ring bridge between the chromophores and CRA core.EA and MALDI-TOF-MS results confirmed that the introduction rate of functional components were nearly 100%.All the polydispersity index?PDI?of three hyper-structured molecules measured by GPC were below 1.24.The glass transition temperature?T_g?determined by DSC of CRA-TXO-PhCz_X-mCP_?100-X??X=100,50,12.5?were 153.9,142.0 and 71.8°C,respectively,indicating good thermal stability.Spin-coating as-prepared three TADF materials doped into mCP as the emitting layer?EML?,repectively,OLED devices were fabricated and measured.All the OLED devices emitted green light.Among them,the CRA-TXO-PhCz₁₀₀-mCP₀-based device showed best compresive performancewith the turn-on voltage of 4.0 V and the maximum brightness of 678.9cd/m².Part two,model luminescent molecule TXO-TPA,azide-containing functional compound TXO-TPA-O-N3 and hypered structured molecule CRA-TXO-TPA₁₀₀ were synthesized and characterized.First,the functional compound TXO-TPA-O-N₃ with an azide end group and core body CRA-Alkyne with eight alkyne end groups were synthesized through the reaction of Ullmann and Suzuki.Then,TXO-TPA-O-N₃ was reacted with CRA-Alkyne via azide-alkyne"click chemistry"reaction to form a hyper-structured TADF molecule CRA-TXO-TPA₁₀₀.HR MS result indicated that the small molecular chromophore TXO-TPA-O-N₃ had been successfully synthesized.EA and MALDI-TOF-MS results of CRA-TXO--TPA₁₀₀ proved that the introduction rate of functional luminescent component was nearly 100%.The PDI of CRA-TXO-TPA₁₀₀measured by GPC was 1.22.The T_g of CRA-TXO-TPA₁₀₀ determined by DSC was136.3°C,exhibiting good thermal stability.Spin-coating CRA-TXO-TPA₁₀₀ doped into mCP as EML,the OLED device was fabricated and measured.The device emited orange light.Its turn-on-light voltage was 4.0 V,and maximum brightness was 841.8cd/m².