Synthesis Of Deep-Blue Materials Based On Tert-Butylanthracene And Their Applications In Organic Light-Emitting Diodes

Organic light-emitting diodes(OLEDs)have become a hot research topic because of their unique advantages such as flexible display,wide viewing angle,fast response,high efficiency,ultra-thin,and low power consumption.In recent years,it is critical to prepare efficient and stable OLED devices due to the acceleration of commercialization in the display and lighting fields.Scientists have made considerable progress in the commercial development of red and green emitters in the three primary colors,while the development of blue emitters,especially deep-blue emitters,remains challenging due to their characteristics of wide band gap and high energy.Therefore,the development of efficient and stable deep-blue emitters is of high importance.Anthracene has a suitable wide band gap and good electroluminescence property,which has been regarded as an excellent building block for blue emitters.Based on this,we have carefully designed and synthesized a series of deep-blue materials,which have excellent fluorescence efficiencies in both aggregate and solution state.In addition,we also designed and synthesized a series of novel room temperature phosphorescent molecules.Through systematic characterization and analysis of these molecules,we have thoroughly discussed the structure-activity relationship of these materials and applied these materials to OLED devices.The detailed studies are as follows:In chapter 2,we designed and synthesized a series of new deep-blue molecules DMAC-TAn-BI,DPAC-TAn-BI,DMAC-TAn-PI and DPAC-TAn-PI based on tert-butylanthracene which modified with acridine and imidazole derivatives,respectively.Through comprehensive characterization of these molecules,we found that they have high solid-state photoluminescence quantum yield(?_F),outstanding thermal stability and excellent bipolar carrier transport ability.The nondoped OLED based on DPAC-TAn-BI has stable deep blue emission,CIE_x,y(0.15,0.15),and its external quantum efficiency(EQE)is up to 5.81%due to the triplet-triplet annihilation(TTA)mechanism.The hybrid white OLED based on DPAC-TAn-BI and Ir(tptpy)₂acac also exhibits a high EQE of 27.6%,and the efficiency roll-off at1000 cd m^-2 luminance is only 2.9%.These results indicate that these novel deep-blue molecules have practical application prospects in flat panel display and illumination.In Chapter 3,we designed and synthesized a series of novel deep-blue molecules TPE-TAn-CN,m Cz-TAn-CN and m2Cz-TAn-CN based on tert-butylanthracene which modified with twisted tetraphenylethene groups,carbazole derivatives and benzocyano groups,respectively.Through comprehensive characterization of these molecules,it is found that they have high?_F values and outstanding thermal stability.Moreover,these novel deep-blue molecules could be used as emitting layers to afford excellent performance in both nondoped and doped blue OLED devices,and the experiment proved that the high efficiency was mainly caused by the TTA mechanism.Nondoped OLED devices based on m Cz-TAn-CN have stable deep blue emission CIE_x,y(0.14,0.12)and high EQE of 7.03%.The EQE of the doped OLED device based on m2Cz-TAn-CN is increased to 7.28%,and the value of its CIE_y is as low as0.09,showing excellent deep-blue emission.These deep-blue emitters designed not only achieve high-efficiency deep blue emission,but also show excellent application potential in both nondoped and doped devices.In Chapter 4,we studied and synthesized two molecules(DPAC-BO and DMAC-BO)with room temperature phosphorescent property.Both of them exhibit deep blue fluorescence and green phosphorescence emission.We analyzed the crystal structure and packing of these two molecules,and tested their photophysical characteristics and stability.In order to further explore their phosphorescence mechanism,we carried out theoretical calculations with QM/MM method,and verified the intersystem crossing process between S₁ and T_1-2through the energy gap and efficient spin-orbit coupling between T₁ and S₀.Due to the excellent photophysical properties of these two molecules,we applied them to doped OLED devices and achieved high EQEs of 1.08%and 1.11%,respectively.Subsequently,the transient electroluminescence spectrum of the device demonstrated that the electroluminescence emission is the combination of fluorescence and phosphorescence.