Synthesis And Optoelectronic Properties Of Bipolar Deep-Blue Emitters Based On Fluorinated Bianthracene Derivatives

White organic light-emitting devices(WOLEDs)have received considerable interest because of their various advantages such as excellent image quality,light weight,easy manufacturability,low cost,large-area,and flexibility in full color displays and solid-state lighting.However,the highly stable and efficient blue materials always keep as one of the most challenging targets of WOLEDs research compared to red and green materials,and it is difficult to satisfy the required Commission International de L'Eclairge(CIE)coordinates(x,y)=(0.14,0.08),defi ned by the National Television System Committee(NTSC).Therefore it has practical significance for the development of excellent comprehensive performance of blue fluorescent materials.This dissertation proposes to combine the specific features of fluorinated compounds and the outstanding properties of anthracene derivatives,to discuss the electronic effects and space effects resulting from effects of substitute groups,and to design and synthesize a novel class of excellent bipolar deep-blue emitters with a non-donor-acceptor structure based on fluorinated bianthracene derivatives,and to study systematically the effect of different fluorine groups on the thermal stability as well as the charge transporting and luminescent ability of the materials in experiment and theory,and finally to achieve substantial increase of colour purity and thermal stability of ideal efficient WOLEDs.In the dissertation,we performed the researches on this topic and the main results obtained are summarized as follows:(1)We synthesized three bianthracene derivatives by using certain size substituent anthraquinone(BA,MBA,TBBA),With the different substitution patterns of the electron-donating groups,such as CH3 and t Bu,the photophysical properties,the energy levels and thermal stability of these BAs are tuned,which are supported by a density functional study of their geometry and electronic structure.Methyl group and tert-butyl group has been introduced to the bianthracene core to suppress the molecular aggregation and tune blue emission more effectively.Multilayered OLEDs were fabricated by using BAs blue materials as the emitting layer(non-doped OLEDs)and the host for1-4-di-[4-(N,N-diphenyl)amino]styryl-benzene(DSAph-doped OLEDs).Non-doped deep blue OLED using TBBA as the emitter gets excellent CIE coordinates of(0.15,0.06)with EQE 3.18%.Moreover,the use of MBA as the host of the blue-emitting dopant DSAph resulted in high-performance OLEDs with a high external quantum efficiency of 9.30%,a high current efficiency of 16.54 cd /A and a high power efficiency of 16.57 lm/W and the pure blue emission with a maximum luminance of over 13800 cd/m.These compounds are a very efficient blue host material because these have quite an effective spectral overlap with the blue dopant such as DSAph.(2)A series of efficient blue host materials of fluorinated 3,3?-dimethyl-9,9?-bianthracene derivatives(MBAnFs)have been successfully prepared by Suzuki coupling reactions.We have demonstrated that the absorption,emission,electrochemical properties,and OLED performances are significantly affected by the introduction of electron-withdrawing substituents such as F and CF3 into the 3,3?-dimethyl-9,9?-bianthracene core,which were supported by theoretical calculations employing the B3 LYP functional.The no-doped EL device with TBBAn-4-F as the emitter achieved an maximum external quantum efficiency(EQE)of 6.11% in the deep-blue visible region with excellent CIE chromaticity coordinates(0.15,0.05)that meet the NTSC standard blue coordinates.Moreover,the use of CBP as the host of the blue-emitting dopant MBAnFs resulted in high-performance OLEDs with the high EQE of 4.57%,4.11%,6.65% and 6.25% in the deep-blue visible region with excellent CIE chromaticity coordinates(0.15,0.05-0.07).Especially,The doped EL device with MBAnFs as the host and DSAph as the dopant achieved an maximum EQE of 8.69%,8.42%,11.76% and7.90%,high CE of 18.63-25.19 cd/A and a high PE of 12.42-25.52 lm/W and the pure blueemission with a maximum luminance of over 20920-23670 cd/m2,respectively,which shows a potential application as an emitter for pure blue devices.(3)A series of efficient blue host materials of fluorinated 3,3?-dimethyl-9,9?-bianthracene derivatives(TBBAnFs)have been successfully prepared by Suzuki coupling reactions.We have demonstrated the photophysical properties and electrochemical properties by theoretical calculations and experiment.The no-doped EL device with TBBAn-4-F as the emitter achieved an maximum external quantum efficiency(EQE)of 3.16% in the deep-blue visible region with excellent CIE chromaticity coordinates(0.15,0.06)that meet the NTSC standard blue coordinates.Especially,The doped EL device with TBBAn-2-F as the host and DSAph as the dopant achieved an maximum EQE of 6.89%,a high CE of 11.20 cd/A and a high PE of 8.72 lm/W and the pure blue emission with a maximum luminance of over 21250 cd/m2,which shows a potential application as an emitter for pure blue devices.Our research show that introduction of a C–F bond or CF3 group may alter the molecular packing and minimize the self-quenching behaviour;HOMO and LUMO levels may be modified by fluorination and the LUMO levels decreased more obviously than the HOMO levels with increasing the highly electronegative fluorine substituents,thus allowing the optimization of the carrier injection and the tuning of the electroluminescent colour.