Preparations Of Narrow-band Red Fluorescence Carbon Dots And Their Application In LEDs

Carbon dots(CDs)has been successfully applied in light emitting devices,solar cells,biological imaging,nanomedicine,photocatalysis and other fields due to its excellent physicochemical properties and biocompatibility.After years of development,significant progress has been made in many aspects:preparation methods,characterization of properties,application researches and other aspects of CDs.At present,there are various methods to prepare CDs,but most of them prepared,the absorption spectra are in the ultraviolet band and the fluorescence spectrum is located in the blue and green spectral regions.There are few successful attempts of strong fluorescence near-infrared CDs,and even fewer successful attempts of near-infrared CDs with narrow bandwidth.However,the application of CDs in display technology and fluorescence imaging requires a narrow band of fluorescent carbon point to improve the imaging quality.Therefore,this thesis is devoted to the study of narrow band red CDs and electroluminescent devices,which were made of hydrophobic CDs(or light emitting diode,LED)and their photoelectric characteristics.The main work with innovative significances are as follows:(1)The narrow red band CDs can be prepared by using phthalocyanine oxide titanium as carbon source and ethanol as solvent.It has unexcited dependent photoinduced red emission,with a peak wavelength of 674 nm and a half-peak width of23.2 nm.The excellent fluorescence characteristics of the narrow-band red CDs were caused by the action of impurities N and Ti in the CDs and the passivation of groups such as-OH and-COOH on the surface and at the edges.(2)The study on the effects of different reaction times on the synthesized red narrow band CDs were investigated by using phthalocyanine oxide titanium as the carbon source and ethanol as the solvent.The results showed that,with different reaction times,the carbonization degree and oxidation degree of these narrow-band red CDs are different,and the lattice defects of impurity N in the carbon cores were different,thus affecting their fluorescence quantum efficiency.(3)Using phthalocyanine oxide titanium as the carbon source and were solvent with ethanol,DMF and DMSO to make CDs,respectively.The researches showed that the solvents had a great influence on the red CDs with narrow band,and the oxidation degree of the CDs was higher in polar solvents,which were conducive to the red shift of the fluorescence wavelength of the CDs.(4)Blue and green hydrophobic CDs were synthesized by pyrolysis with citric acid as reaction precursor and cetylamine as passivation agent.The results showed that the fluorescence intensity of CDs was different with the reaction time.The reason was that the relative number and oxidation degree of C-O,C=O and Ti-O groups changed significantly with the reaction time.(5)The light-emitting diodes(LEDs)with CDs as emitting layer were prepared by ITO/PEDOT:PSS/poly-tpd/PVK:CDs/TPBi/LiF/Al devices structures,and the effects of different doping concentrations on electroluminescence were studied.The results showed that the devices have good photoelectric characteristics and the maximum brightness reached 450 cd/m~2,which was closely related to the exciton transport between PVK:CDs subject and object.