Synthesis, Characterization And Properties Of Monodisperse Multi-armed Conjugated Macromolecules With Electron-withdrawing Functional Groups For Organic Electroluminescence And Lasing Applications

Development of new structure, excellent performance organic optoelectronic materials is one ofthe important ways to solve the bottleneck of the organic electroluminescent and organic laser field,which is of great scientific and practical significance. Multi-armed structure of organicphotoelectrical materials designed by our group in previous studies achieved good deviceperformance. In addition, a large number of studies have shown that the benzene cyano end groupsgreatly facilitate electron injection/transport capability.In order to improve the efficiency of the device, we put forward the design thought that usingthe benzene cyano as an end group to modify the multi-armed structural materials. So wesynthesized a series of star-shaped molecules, four-armed monodisperse fluorene-pyrene derivatives,six-armed monodisperse fluorene-truxene derivatives and three-armed monodispersefluorene-triazatruxene.The four-armed monodisperse macromolecules had shown good thermal stability andamorphous morphology. This series of molecules as emitting layer electroluminescent devices wereprepared to obtain the relevant parameters of luminescent properties, and compare the relationshipbetween them. The double-layer devices were fabricated with the configuration of ITO/PEDOT:PSS (40nm)/T1-T3(80nm)/1,3,5-tris (N-phenylbenzimidazol-2-yl)-benzene (TPBI)(40nm)/LiF(0.5nm)/Al (100nm). The best EL performance is achieved by T1with a maximum currentefficiency ηc, maxof3.52cd A-1, and a maximum brightness (Lmax) of9194cd m-2. Due to its bettermorphology stability, T1-T3were studied for optically pumped laser emission.the ASE threshold(Eth) was30nJ pulse-1,36nJ pulse-1and34nJ pulse-1at25oC, respectively.The six-armed monodisperse macromolecules also had shown good thermal stability andamorphous morphology. This series of molecules as emitting layer electroluminescent devices wereprepared, but the performance was not satisfactory. Howere, it is excited that the ASE threshold (Eth)was very low,26nJ pulse-1and30nJ pulse-1at25oC, respectively.The three-armed monodisperse macromolecules also had shown good thermal stability and lowLUMO energy level, which was advantageous to the electronic injection and transmission, thusimprove the organic electroluminescent device performance.