Design,Synthesis And Electroluminescent Properties Of Novel Anthracene-Based Organic Electroluminescent Materials

Since Tang et al.first realized the electroluminescence of conjugated organic light-emitting materials by evaporation process in 1987,arduous efforts have been made by researchers for the development and growth of organic light-emitting materials.The first generation of organic light-emitting devices?OLEDs?are fluorescent molecules based devices,which can only utilize the singlet excitons,so the device efficiency is generally low.The second generation OLEDs are phosphorescent OLEDs?PhOLEDs?which based on heavy metal complexes.Due to the spin-orbit coupling effect of heavy metal complexes,these devices can realize high efficiency by utilize the 75%triplet excitons.The device efficiency of green and red phosphorescent improved very rapidly which is valuable in the practical application,but,the efficiency roll-off of blue PhOLEDs is very serious and simultaneously the lifetime stability have not been solved.The third generation OLEDs are thermally active delayed fluorescence?TADF?devices.Through reverse intersystem crossing?RISC?process from the triplet excited states to the singlet excited states,a 100%exciton utilization rate can be realized.High efficiency green,yellow and orange TADF materials have been developed,but the efficiency roll-off is generally serious,especially in the case of blue and deep-bule TADF materials.What's more,for highly efficient PhOLED devices and TADF devices always need a complicated device fabrication process to weak the quenching effect which will increase the cost of practical application and greatly limits the practical application of PhOLED devices and TADF devices.Therefore,it is urgent to design a kind of nondoped organic electroluminescent materials with simple fabrication process,high device efficiency and low efficiency roll-off.In this thesis,a series of efficient organic electroluminescent materials are designed which use anthracene unit as the core and different electron donor and electron acceptor groups bonded at 9 and 10 position of anthracene.The details are as follows:1.Two organic electroluminescent materials with anthracene as the central group and electron donor?triphenylamine and diphenylamine?and electron acceptor?4,6-diphenyltriazine?groups bonded at 9 and 10 positions of anthracene are designed and synthesized.TPAAnTrz and DPAAnTrz both have good thermal stability.In the film states the fluorescence quantum efficiencies are 56%and 65%,respectively.Two nondoped OLEDs are fabricated.The maximum current efficiencies of the two devices are 13.21 cd A^-1and 10.31 cd A^-1,respectively,and they can still maintain high efficiency at high brightness(10000 cd m^-2)which exhibit negligible efficiency roll-off.2.Three bluish-green organic electroluminescent materials 3CzAnTrz,pCzAnTrz and mCzAnTrz are synthesized by introducing phenylcarbazole and changing the bonding positions of phenylcarbazole.These compounds all have good thermal stability and high quantum efficiency in thin film states,which enable them to fabricate nondoped OLEDs.The maximum current efficiency of the three devices are 13.34 cd A^-1,11.19 cd A^-1 and 8.74 cd A^-1,respectively.The maximum power efficiency are 11.59 lm W^-1,9.25 lm W^-1 and 6.44 lm W^-1,and the maximum external quantum efficiency are 5.44%,5.54%and 4.71%,respectively.The devices can still maintain high efficiency at high brightness which can exhibit negligible efficiency roll-off at high brightness.The emission peak of electroluminescence spectra of the three devices are 488 nm,479 nm and 475 nm,respectively.3.Two skyblue organic electroluminescent materials are designed and synthesized.These two compounds 3CzAnPyCN and pCzAnPyCN both have good thermal stability.The fluorescence quantum efficiency are 65%and 61%,respectively in the film states.Nondoped OLEDs are fabricated by using these two materials.The maximum current efficiency of the two devices are 17.73 cd A^-1 and 14.18 cd A^-1,the maximum power efficiency are 15.40 lm W^-1 and 13.12 lm W^-1,and the maximum external quantum efficiency are 8.07%and 8.13%,respectively.The efficiency roll-off of the two nondoped devices was relatively small at high brightness.4.Two blue organic electroluminescent materials are designed and synthesized by introducing p-cyanobenzene,which has weak electron absorption ability.Two compounds3CzAnBzt and pCzAnBzt both have good thermal stability.The fluorescence quantum efficiencies are 52%and 59%,respectively in the film states.Nondoped OLEDs are fabricated used these two materials which exhibit excellent device performance.The maximum external quantum efficiency of the two devices are 10.06%and 9.23%,respectively,and the device efficiency of the two nondoped devices can still maintained higher when the brightness is 1000 cd m^-2.The color coordinates of the two devices are?0.14,0.14?and?0.14,0.10?,respectively.5.Two deep blue materials m CzAnBzt and m2CzAnBzt are designed and easily synthesized by Suzuki coupling reaction.Due to the introduction of one or two carbazole units at the meta-position of 4-?10-phenylanthracen-9-yl?benzonitrile,these two compounds both have twisted spatial structure and weak intermolecular interactions.And excellent deep blue electroluminescence performances are realized when used mCzAnBzt and m2CzAnBzt as emitters in the nondoped devices.The maximum current efficiency of the two devices are|5.71 cd A^-1 and 6.20 cd A^-1,the maximum power efficiency are 4.91 lm W^-1 and 5.40 lm W^-1,and the maximum external quantum efficiency are 7.95%and 7.36%,respectively.The color coordinates of the two devices are?0.15,0.07?and?0.15,0.09?.6.Two deep blue organic electroluminescent materials are synthesized by introducing p-dimethylbenzene to increase the twist between molecules and reduce the charge transfer.The two compounds 2M-ph-pCzAnBzt and 2M-p CzAnBzt both have good thermal stability.The fluorescence quantum efficiency are 65%and 60%,respectively in the film states.Nondoped OLEDs are fabricated and exhibit excellent performance.The maximum current efficiency of the two devices are 5.95 cd A^-1 and 4.95 cd A^-1,the maximum power efficiency are 5.43 lm W^-1 and 4.57 lm W^-1,and the maximum external quantum efficiency are 10.44%and 8.08%,respectively.The color coordinates of the two devices are?0.151,0.057?and?0.151,0.061?,respectively.