Synthesis And Luminescence Properties Of Coumarin Fluorescent Materials

Light-emitting diodes(LED)look promising as a new type of low-carbon display devices and lighting sources.They have the advantages of low energy consumption,high luminous intensity,light weight,high contrast and environmental protection.And with the maturity of UV-LED technology,the exploration of fluorescent materials with good luminous performance plays an important role in their applications.Coumarin fluorescent materials,as an important organic fluorescent materials,that could regulate their luminous color and brightness by introducing different substituents,which has a very wide range of applications.In this paper,a series of coumarin derivatives with strong fluorescence both in solid and liquid state were designed and synthesized by introducing different substituents into the 3-position and 7-position and so on of coumarin skeleton.And their applications in LED lighting devices were studied.The main research contents are as follows:1.The LED solid-state lighting diodes are obtained by placing the coumarin fluorescent materials of hexyloxy at the 3-position and 1-naphthalene(NCM1)and 2-naphthalene(NCM2)at the 7-position in the ultraviolet chip,respectively.Through their luminescence-voltage curves,we found that all thedevices had a low turn-on voltage(2.8V).The device NCM2 had a higher luminance than the device NCM1.Compared with the device NCM1,the photoluminescence peak of device NCM2 had a red shift of 80 nm,and the devices NCM1 and NCM2 emitted blue and cyan light with CIE coordinates of(0.231,0.231)and(0.198,0.368),respectively.2.Based on the above research process,four coumarin fluorescent materials with twisted conformations were synthesized by introducing diethylamino(NCM3 and NCM4)and 4-trifluoromethyl phenyl(NCM5 and NCM6)at the 7-position.We found that coumarin derivatives with diethylamino group had a larger intramolecular charge transfer process(ICT).The powder of2-naphthyl substituent compound NCM4 showed yellow fluorescence under the ultraviolet lamp.Using the UV chip to excite compounds NCM3-NCM6,successfully made into LED lighting devices,respectively.The luminescent brightness of devices NCM4 and NCM6 were higher than that of NCM3 and NCM5,and the brightness of device NCM4 is the highest.From their PL spectra,we found that the peak of the devices based on 2-naphthyl coumarin derivatives had a red-shifted compared with that of the devices based on1-naphthyl group.The devices NCM3 and NCM4 emitted cyan and green light,CIE coordinates were(0.288,0.415)and(0.22,0.483),the devices NCM5 and NCM6 emitted blue and cyan light,and CIE coordinates were(0.226,0.235)and(0.192,0.268),respectively.3.Two coumarin fluorescent materials were synthesized by introducingbenzo at the 5,6-position of coumarin and 1-naphthalene(NCM7)and2-naphthalene(NCM8)at the 3-position.Their luminescence properties both in solid and liquid state were studied.It was found that the fluorescence quantum yield of NCM8 was higher than that of NCM7,and the emission peak was red shifted.Through their theoretical calculations,we also found that the configuration of NCM8 was better and had a larger ICT process.And the LED was successfully fabricated by encapsulated NCM8 with better luminescence in ultraviolet LED chip.The LED emitted green light with CIE coordinates of(0.369,0.512).