Synthesis Of Organic Electroluminescent Materials And Investigation Of The OLEDs Based On Delay Fluorescence Mechanism

Thermally activated delayed fluorescence?TADF?materials have developed quickly these years due to its unique advantages in the field of organic light-emitting devices?OLEDs?.It has been considered as the next generation of organic electroluminescent materials after phosphorescent materials.In order to further promote such new fluorescent materials research progress in the field of OLEDs,and develop excellent TADF based light-emitting devices.We designed and synthesized a series of efficient TADF materials and discussed their physical,chemical and electroluminescent properties.In addition,these materials are studied of spectrum,space steric effect and devices,achieveing some results:1.We designed and synthesized six kinds of TADF materials:oPTBC,oATBC,oSTBC,mPTBC,mATBC,mSTBC and tesed their physical and chemical properties.Six kinds of materials all have small electronic exchange to inverse system crossing for the triplet excitons.The charge transfer absorption peak is all about 420 nm,and photoluminescence peak are located at 561 nm,509 nm,497 nm,518 nm,480 nm,474nm respectively;The decomposition temperature of the materials are high enough which can guarantee good form in the process of fabricating devices.2.We further studied the electroluminescent device of both isomers oPTBC and mPTBC,and put forward a simple method to adjust the spectrum of their devices.Both electroluminescent devices exhibited excellent EQEs of 18.1%and 17.8%for mPTBC and oPTBC respectively,and the brightness was more than 10000 cd m^-2.The electroluminescent peak of oPTBC was 540 nm,and mPTBC electroluminescent peak was 518 nm.The roll-off of the two kinds of devices were better than that of most TADF devices.Our work successfully demonstrated that the simple changing position of electron-withdrawing groups can regulate device spectrum,and does not affect the other key performances of the devices.3.We further studied the electroluminescent devices based on oATBC,oSTBC,mATBC,mSTBC,and researched the influence of the space steric hindrance to materials and devices.The stokes shifts of these compounds gradually decreased with the increase of the space steric hindrance:129 nm,92 nm,54 nm and 36 nm;The color purity of four devices also gradually improved,the full width at half maximum?FWHM?were 90 nm,89 nm,80 nm and 89 nm respectively.All devices were showed high external quantum efficiencies?EQEs?.the green device based on oSTBC exhibited EQE of 21.4%,and the blue devices based on mSTBC is as high as 20%.Our work not only get a series of efficient TADF devices,but also give some ideas for the follow-up study to design high performance TADF emitters.The work of this paper enriched TADF material types,and got a series of efficient OLED devices,and promoted this kind of new fluorescent materials research progress in the field of OLEDs,providing the basis for the follow-up study of TADF materials.