Syntheses And Characterization Of Fluorenone And Nitrogen-bearing Heterocyclic Thermally Activated Delayed Fluorescent Materials

Pure organic emissive materials with thermally activated delayed fluorescence (TADF) have drawn much attention in the fabrication of OLEDs over the last few years, for their high efficiency, low cost, readily color-tunability, and abundant variety. Thus, the design and synthesis of higly stable blue materials with good color-purity are very demanding and challenging. In this thesis, a series of TADF compounds have been designed and synthesized. Their UV-vis, NMR, photoluminescence and electroluminescence properties have been studied.Four novel fluorenone organic compounds are reported in chapter one. These compounds exhibit yellow to red emissions. The emissions of these compounds in various solvents reveal that thes compounds have strong solvent effect. The observation could be explained as radiation relaxation in a low energy of localized excited state excition radioluminescence in non-polar solvent and intramolecular charge transfer radioluminescence in polar solvent. These compounds show thermally activated delayed fluorescent property according to the analysis of time-dependent emission spectra in air-equilibrated and degassed toluene.Three novel push-pull type TADF compounds with nitrogen-rich 3,7,11-triphenyltris([1,2,4]triazolo)[4,3-a:4',3'-c:4",3"-e][1,3,5]triazine as electron acceptor and carbazole,3,6-di-tert-butylcarbazole or 9,9-Dimethyl-9,10-dihydro-acridine as electron donor are reported in chapter two. Theoretical calculation showed that these compounds have high triplet level and exhibit purple to blue emissions. Superior thermostability and film-forming property of N9ocz and N9otbucz can be used as efficient TADF materials. Solution-processed OLEDs containing N9pyd in the emissive layer demonstrated excellent device performances and achieve a maximum brightness of 3226cd/m2, a peak external quantum efficiency of 6.87% and a turn-on voltage of 5.7V.Two novel TADF compounds of TAZocz and TAZotbucz are presented in chapter three. The energy gap between singlet and triplet in these compounds is 0.16 eV and 0.15eV, respectively. These compounds exhibit high photoluminescent quantum yields (PLQY) near 100% with a doping concentration of 5wt% in PMMA. Compound of TAZotbucz exhibits high PLQY in nitrogen-saturated toluene (100%). Solution-processed OLEDs containing TAZocz in the emissive layer demonstrated excellent device performances, using DPEPO as hole-blocking layer and TPBI as electron-transporting layer. OLED (Device F) achieve a peak external quantum efficiency of 9.02%, a maximum brightness of 5754cd/m2, a turn-on voltage of 6.1V and wavelength peak at 471nm. It's a purity blue TADF device.