Design And Construct High Efficiency Organic Solid Luminescent Materials By Twisted Molecular Configuration

Organic luminescent materials are widely used in the fields of organic light-emitting diodes,security anti-counterfeiting,biological imaging and optical storage,and are a research hotspot of luminescent materials.Compared with inorganic and metal luminescent materials,organic luminescent materials have advantages of lower cost,easy regulation and control of structure,wide variety and the like.However,the intrinsic aggregation caused quenching(ACQ)effect of most conventional organic solid-state luminescent materials leads to weak or even no luminescence in concentrated solution and aggregation state,which limits the practical application of organic luminescent materials in many fields,such as OLED.The distorted molecular configuration can avoid the quenching effect caused by π-π interaction between molecules in the aggregation state,and obtain the solid efficient luminescence of organic compounds.The specific work of this paper is as follows:(1)A novel luminescent material BP2 TPAN with highly twisted molecular configuration was prepared by Buchwald-hartwig C-N coupling reaction of bromotriphenyl acrylonitrile and N,N’-diphenyl-1,4-phenylenediamine.The results show that the compound has typical aggregation-induced emission(AIE)characteristics,and the photoluminescence quantum yield can reach 74.3 %;The fluorescence emission wavelength of the solid sample shifted from 540 nm to 580 nm under the action of force stimulus,which showed the effect of mechanochromic.The thermal decomposition temperature and glass transition temperature of BP2 TPAN are 414 ℃ and 96 ℃,respectively,which showed good thermal stability.The light emission wavelengths of the doped and undoped OLED devices prepared by the compound are 570 nm and 530 nm respectively,and the external quantum efficiency of the device is 1.1% and 3.1% respectively.The dual-color light emission of the device is realized by adjusting the device process.(2)D-π-A compounds BTPAAN and BTMPAAN were synthesized by knoevenagel reaction of benzothiazole-2-acetonitrile with triphenylamine and its derivatives with aldehyde group.The results shows that the two compounds with twisted configuration have aggregation-induced emission enhancement(AIEE)properties,and the photoluminescence quantum yields of the crystals are 24.53 % and 25.04 %.With the increase of the polarity of solvent,their emission spectra are red shifted gradually,and the photoluminescence quantum yield is decreased gradually,showing the effect of discolouration common to D-π-A compounds.The thermal analysis shows that the thermal decomposition temperature/glass transition temperature of BTPAAN is 135℃ and 353℃,respectively,showing good thermal stability.The crystal samples of the two compounds have unusual blue shift phenomenon under the action of force,especially BTMPAAN molecule,which changes from red light emission to orange light emission under the action of force,and the emission peak position is blue shifted by 62 nm.(3)The design and construction of organic room temperature phosphorescent materials can not only improve the efficiency of OLED devices,but also greatly reduce the cost of OLED devices.The optical properties of 9,9-diphenylfluorene(DPF)and its brominated compounds(BDPF,DBDPF)with distorted spatial configuration were studied.The results shows that they hardly emit light in solution and the photoluminescence quantum yield is as low as 0.54 %,but photoluminescence quantum yield in crystal state can reach 59.66 %(BDPF).In the crystalline state,it has room temperature phosphorescence emission in addition to fluorescence emission,and the phosphorescence lifetime is 29ms(BDPF),showing crystallization induced fluorescence/phosphorescence double emission(CIDE)characteristics;The photoluminescence quantum yield and lifetime can be regulated by the content of halogen bromine atoms;Their polymethylmethacrylate(PMMA)doped films can also emit room temperature phosphorescence effectively,which indicates that these compounds also have the ability of phosphorescence emission in amorphous state,which provides a certain reference value for the design and construction of OLED organic room temperature phosphorescence materials with high efficiency and low cost.