Synthesis And Characterization Of Coumarin Photoelectric Materials And Application In OLED

Organic light-emitting diodes(OLEDs)have many advantages,such as self-luminous,wide viewing angle,thin thickness,high contrast,fast response,low power consumption,large usable temperature range,low cost,flexible panels and so on,applied to displays,light sources and other areas.In recent years,organic/polymer luminescent materials and device fabrication have attracted the attention of scientists due to their advantages of light weight,simple preparation process,and the ability to fabricate flexible devices.Currently,the performance of the red and green materials of OLEDs is relatively good,such as the life expectancy of the OLEDs,which basically meets the requirements of industrial mass production,while the Blue-ray materials are lagging behind.Therefore,it is very urgent to develop blue light emitting materials.Based on the above reasons,this paper is devoted to synthesis small molecule organic blue luminescent materials with low cost,high luminous efficiency,and good thermal stability,improving the properties of the materials and improving the efficiency of OLEDs.The specific research content can be divided into the following three parts:In the first part,three novel luminescent materials,1-(p-(7-diethylamino-coumarin-3-yl)phenyl)pyrene(NCP),1,6-di-p-(7-diethylamino-coumarin-3-yl)phenyl)pyrene(NCPC)and 9,10-di-p-(7-diethylamino-coumarin-3-yl)phenyl)anthracene(NCAC)were synthesized with N-coumarin as the core and N-coumarin as the luminescence group.Because germanium or antimony has good conjugate and rigid structure and is a typical blue light material,N-coumarin has high fluorescence quantum yield,large Stokes displacement,and good light stability,so the three materials have good fluorescence quantum yield,excellent thermal stability.The UV-vis absorption,cyclic voltammetry,lifetime,thermal stability,molar extinction coefficient and electroluminescence of the target compounds NCP,NCPC and NCAC were studied.The devices were fabricated by evaporation.The device structure was: ITO / TAPC(20 nm)/TBADN: compound NCP(x wt%,30 nm)/TPBI(50 nm)/Liq//Al(100 nm),where NCP is doped in TBADN material,TAPC is hole transport material,TPBI is electron transmission material.When the doping concentration ratio was 4%,7%,10% and 13%,the device's luminous intensity,current efficiency,external quantum efficiency,and electroluminescence spectra were studied.It was found that when the doping concentration was 10%,the maximum brightness of 8165 cd/m2 was reached,the current efficiency was up to 6.13 cd/A,the external quantum efficiency was up to 2.75%,and the photoluminescence spectra and the electroluminescence spectra were consistent,emitting blue light.In the second part,three luminescent materials,7-(N,N'-diethylamino)3-4,4'-biphenyl)-coumarin(b1),7-(N,N'-diethylamino)-3-4,4'-di(coumarin-3-yl)-biphenyl(b2)and 4,4'-di(cou-marin-3-yl)-biphenyl(b3),with N-coumarin as luminophore and biphenyl as bridge were designed.Studies have shown that the diethylamino electron-donating group has a great influence on the luminous efficiency,thermal stability and solubility of the luminescent material.The three compounds have poor fluorescence and quantum yield and despite poor solubility,but have good stability.The fluorescence emission spectra of b1,b2 and b3 are at 484,478 and 430 nm,respectively.And all belong to blue light emission.In addition,the LUMO levels of the three compounds b1,b2 and b3 were-2.48,-2.40 and-2.04 e V,respectively.And the HOMO levels were-5.11,-5.07 and-5.05 e V,respectively.An OLED device was fabricated with b2 and b3 as doping materials.The device structure was: ITO / TAPC(20nm)/ TBADN: compound b1 or b2(xwt%,30nm)/TPBI(50nm)/Liq/Al(100 nm).The device performance test results show that when the doping concentration of b2 is 10%,the device has a maximum brightness of 5135 cd/m2,power efficiency up to 2.1 lm/W,external quantum efficiency up to 2.3%,electroluminescence spectra display as blue light emission.From the device performance point of view,b2 has better performance than b1.In the third part,thiophenes are widely used in electroluminescent and dye-sensitized solar cells.The thiophene-substituted N-coumarins are used as the luminophores,and thorium as the core and benzene as the bridge,respectively.1-(p-(7-diethylamino-coumarin-3-yl)thiopheneyl)pyrene(DZSFB),7-(diethylamino)-3-(5-(4-(7-(diethylamino)-coumarin-3-yl)phenyl)thiophen-2-yl)-coumarin(SBS),7-(diethylamino)-3-(5-(4-(coumarin-3-yl)phenyl)thioph en-2-yl)-coumarin(DZSBS)Three coumarin derivative luminescence materials with thiophene groups,because thiophene can broaden the absorption range,enabling both UV absorpti-on and fluorescence emission to be red-shifted,thereby adjusting light color and increasing electron transmission performance.The UV-vis absorption,cyclic voltammetry,lifetime,thermal stability of the target compounds SBS,DZSBS and DZSFB were studied and their density functional calculations were performed.The results are similar to Chapters 2 and 3.The spectrum of these compounds are red-shifted,the thermal stability is reduced,and the luminous efficiency is also reduced(the hetero atom effect of the S atom on the thiophene ring).The conclusions are as follows:1.When the benzene ring is replaced by the thiophene ring,the introduction of the thiophene ring reduces the HOMO energy level of the molecule;2.The introduction of the thiophene ring makes the emission spectrum red-shift and increases or decreases the number of thiophene rings.Adjusting light color can use thiophene ring design to adjust light color molecules;3.the introduction of thiophene rings reduces the melting point,thermal decomposition temperature,increased solubility.