The Research On Preparation And Longer Deep Red Luminescent Properties Of CuInS_2-xSe_x@CuGaS₂ Core-shell Quantum Dots

Among the ?-?-? group quantum dots,especially copper-based quantum dots,not only are green and environmentally friendly and non-toxic,they also have the advantages of simple preparation process,low cost,excellent fluorescence performance,and long luminescence life.It has broad prospects in many application fields such as light-emitting diodes,solar cells,and biological imaging,but its red fluorescence performance needs to be further improved to be suitable for practical applications.In this paper,the CuInS₂system is doped with Se^2-and the reaction conditions are controlled to obtain CuInS_2-xSe_xquaternary quantum dots.The other achieved CuInS_2-xSe_xquaternary quantum dots through S^2-and Se^2-anion exchange,and studied the ion exchange process during the reaction.Finally,through the coating process,the surface defects of the nuclear quantum dots were passivated,the fluorescence performance was improved,and the deep red CuInSSe@Cu Ga S₂core-shell quantum dots were obtained.The main work is as follows:(1)Using the one-pot method,CuInS_2-xSe_xquantum dots were synthesized with different Se^2-doping at 210?,and their lattice structure,morphology,fluorescence and absorption spectra were analyzed.Studies have shown that the samples doped with different Se^2-elements present a regular tetrahedral chalcopyrite structure and have good crystal grain dispersion and uniform size distribution.Under 450 nm excitation light,with the increase of Se^2-doping content,the fluorescence emission wavelength gradually red shifts and the luminous intensity decreases.(2)In order to explore the influence of different methods on the synthesis,we used high temperature injection method to inject Se precursors with different contents into CuInS₂to synthesize CuInSSe quantum dots.With the increase of Se^2-injection content,the morphology and crystal structure of CuInSSe quantum dots did not change.When Se^2-and S^2-are introduced for ion exchange,the fluorescence spectrum is obviously red-shifted.Analysis shows that a copper-deficient and indium-rich element distribution is formed in the CuInSSe quantum dots,and the exchange of Se^2-and S^2-is not complete.Even an excessive Se^2-concentration cannot promote the complete exchange of Se^2-.Maintaining the injection concentration of Se precursor at 1 mmol,the effect of reaction time on CuInSSe quantum dots was analyzed.Studies have shown that as the reaction time increases,the grain size of CuInSSe quantum dots remains almost unchanged,the crystal structure is a regular tetrahedral chalcopyrite structure,the fluorescence emission peak is red-shifted,and the intensity of the secondary peak at 825 nm gradually increases.In the process of Se^2-and S^2-anion exchange,the Se^2-content in CuInSSe quantum dots initially increased and then remained unchanged.The ligand component in the two components of the S component increases,indicating that the Se^2-and S^2-anion exchange maintained a dynamic balance at this time.(3)The CuInSSe@CuGaS₂core-shell quantum dots were synthesized.On the basis of the above work,the synthesized CuInSSe quantum dots were used as the core and injected into a certain concentration of Cu Ga S₂precursor solution,and the thickness of the epitaxial shell was adjusted by adjusting the injection content of the CuInSSe core.As the injected core content decreases,the thickness of the Cu Ga S₂epitaxial shell grown on the core surface will gradually increase.Studies have shown that CuInSSe core and Cu Ga S₂shell are both chalcopyrite structures,and CuInSSe@Cu Ga S₂core-shell quantum dots have good dispersibility,maintain the morphology of regular tetrahedrons,and have relatively uniform particle size distribution.With the decrease of nuclear injection content,the PL peak of CuInSSe@Cu Ga S₂core-shell quantum dots blue shifts,and the fluorescence intensity increases.The time-resolved spectroscopy test shows that the coating can passivate defects on the nuclear surface,reduce non-radiative relaxation,enhance radiation relaxation,and improve the luminescence performance of quantum dots.