Design,synthesis And Photoelectric Properties Study Of D-A Electroluminescent Materials Based On Phenothiazine As Electron Donor

In recent years,organic light-emitting devices(OLED)have become the most popular flat panel display industry in the world.Because of its advantages of self-luminescence,wide viewing angle,fast response time,high luminous efficiency and wide range of material selection,it is regarded as the next generation of “Star” flat panel display technology.For the development of OLED,the exploitation of new materials is very important.So,now international puts forward the design and development of organic donor acceptor(D-A)fluorescent molecules,in order to obtain cheap and efficient light emitting materials and devices.D-A type fluorescent molecule can make the carrier transport balance of electron and hole in emitting layer with high composite efficiency,and high luminous efficiency due to it has both electron transporting group and hole transporting group,as the emitting layer material.The electron donor and acceptor group selection is very important for the design and development of D-A type materials.Therefore,based on the selection of phenothiazine as electron donor groups,choose different acceptor groups,by changing the structure of the acceptor group,and the bonding relationship(meta-,para-)between the donor and acceptor,exploring photophysical properties,fluorescence excited state properties and effects of electroluminescent properties,and studying the relationship between structure and properties,and for the design of high efficiency and practical application of the molecular.This is very meaningful.The main contents are as follows:1.We selected 10-Butyl-phenothiazine as the donor and 2-phenyl-1,3,4-oxadiazole as the acceptor to construct novel D–A molecules.Two novel D–A molecules(PO and PPO)were designed and synthesized,and the effects of molecular structure(the torsion angle and distance between donor and acceptor)on the properties of organic light-emitting diodes(OLED)were studied.The experimental results demonstrated that only one phenyl ring was inserted into the D–A molecule,which increases the torsion angle and the distance of the D–A,and improves the charge-transfer(CT)state characteristics of PPO.The dipole moments(?e)of the excited state and time-resolved PL decay with one lifetime indicate the PPO forming a special exciton state(hybrided local charge transfer),which is possibly beneficial for achieving good device performance.Using PPO as emitting layer,the doped OLED has luminous efficiency of 15.2 cd A-1,maximum brightness of 25000 cd m-2 and external quantum efficiency of 5.4%,which are higher than PO-based doped OLED(luminous efficiency of 7.4 cd A-1,maximum brightness of 16000 cd m-2,external quantum efficiency of 2.9%).2.10-Ethyl-phenothiazine is selected as the donor and imidazole derivatives are used as the acceptor to construct four novel D–A molecules.We systematically studied the influence of the change of the electron acceptor group structure and the bonding relationship(meta-,para-)between the donor and acceptor on the photophysical and electroluminescent properties of fluorescent molecules.Among them,compound PBI with 1,4,5-triphenyl-1H-imidazole as electron acceptor group,due to the distorted structure and smaller conjugated degree of this group,makes the PBI-based undoped device emits blue light(?EL = 460 nm),but the luminous efficiency is low(3.4 cd A-1).For compound PTHPPI with phenanthro[9,10-d]imidazole as electron acceptor group,between the electron donor and acceptor groups embedded in benzene conjugated bridge,and donor and acceptor by para-bonding.Compound PHPPI has good conjugate and high conjugation degree,and on the basis of the existence of a localized(LE)excited state,the electron excited state has a charge transfer(CT)excited state,the emission wavelength of the undope device is 496 nm,and the luminous efficiency(11.1 cd A-1)is the highest among four compounds.