| Currently,The market of electronic products using Light-emitting diode(LED),Liquid crystal display(LCD),Cathode-ray tube(CRT)and Organic light-emitting diodes(OLEDs)which rising up in recent years as the main material of displayer.OLEDs had attracted large numbers of scientists' attention because of its low cost,high brightness,wide angle,fast response,low work voltage,full-color light-emitting,wide working temperature range,high luminous efficiency and useful for produce of large size and flexible panel features.The luminescence performance of OLEDs not only determined by the synergy between the functional layers,but also by the structure and properties of the emitting layer.Anthraquinone and its derivatives with polycyclic structure were widely used in natural world and the production field of technology.Anthraquinone compounds had applied to the organic photoelectric functional material and optical sensors.Anthraquinone contains two carbonyl structure,so that has ability to accept electronic preferably.Simultaneously,the coupling constant between the lowest triplet and the ground state was 54cm-1.As shown in the result of the experiment,the room temperature phosphorescence peak of anthraquinone is 540 nm and 580 nm.Anthraquinone group has a wealth of chemical reaction sites,all sites on the benzene ring can be chemically modified by electrophilic substitution reaction.Theoretical simulation geometry indicated that the material system introduce anthraquinone with planar rigid structure will suppress the molecular vibration in a certain extent,in order that reduce the proportion of the nonradiative transition up to Improve the luminous efficiency.All of this indicates the importance of anthraquinone group in organic photoelectric functional material.In this paper,we use anthraquinone as the acceptor group and the donor group we choose carbazole group and triphenylamine whose energy level of molecular frontier orbital HOMO is higher.We obtained 6 twisted molecules with charge transfer state by changing the number of donor?the electron donating ability and connection ways between the donor and acceptor.And then we explore the relationship among molecular structure?photophysical properties and the characteristics of excited state.We get the molecule with donor-acceptor conformation of twisted charge transfer state.The weak binding energy of this molecule can help to adjust the separation degree between the molecular frontier orbital HOMO and LUMO.Thus the material will give out light by means of molecular relaxation under conjugated condition to form intramoleculear charge transfer state.We make further efforts to design bilateral D-AD type molecule to disperse the center of charge,which can help break the exciton statistics limit.Combined with theoretical calculation we know that the larger distortion angle and lose range between donor acceptor and carboxide of 1,5Anthraquinone molecular system will lead to intermolecular charge transfer interaction so that the fluorescent emission will be quenched to form a dark state with no radiation.So it can be seen that we should consider to modify the 2,6Anthraquinone whose conjugated degree is larger.The 2,6Anthraquinone molecule is benefit for adjusting the separation degree between the molecular frontier orbital HOMO and LUMO to balance the electricity exciton utilization rate and the luminous efficiency.Lastly,we exchange the carbazole group to triphenylamine group for its lower energy gap to anthraquinone.By adjusting the energy level matching degree between the donor and acceptor,we can get a molecule with large conjugated structure which can help to the ratio of intramolecular charge transfer degree.Then the large intramolecular charge transfer degree of the material can not only make the color red shift but also decrease the energy level of T1-S1,which will help to reverse intersystem crossing from T1 to S1 and then form a thermally activated delayed fluorescent material to break the exciton statistics limit. |
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