Preparation And Luminescent Properties Of Sulfides And Selenides Multinary Quantum Dots

Quantum dots are nanocrystallines that their radius are smaller than the exciton Bohr radius,the particle size is generally between 1 to 10 nm.Quantum dots are new type of functional materials in recent years.They have unique quantum confined effect and light-emitting adjustable which make them have been widely used in a variety of fields such as LED,bioimaging,solar cell and laser.Compared to current research of II-VI and IV-VI semiconductor quantum dots,I-III-VI semiconductor quantum dots have attracted much attention because they contain no toxic heavy metals such as cadmium and lead.And their emission wavelength ranges cover the visible light area and can be extended to near infrared region at the same time.In our paper,thermal injection method is used to prepare a series of ZnCuInS/ZnS and CuInSe/ZnS and Mn doped ZnCuInS quantum dots.We investigated the luminescence properties and thermal stability through PL spectra at room temperature and temperature-dependent PL spectra at low temperature.The main research contents of this paper are as follows:ZnCuInS core and ZnCuInS/ZnS(ZCIS/ZnS)core/shell quantum dots(QDs)were prepared by thermal injection method.Both emission spectra and absorption spectra shift to the direction of short wavelength that ZnCuInS core becoming small because of forming ZnCuInS/ZnS core/shell structure.The luminescence lifetime and temperature-dependent photoluminescence(PL)spectroscopy of ZnCuInS core and ZnCuInS/ZnS core/shell quantum dots(QDs)were investigated to understand the influence of ZnS shell on the PL mechanism.The emission peak position,the full width at half maximum(FWHM)of the PL peak and PL intensity of quantum dots as a function of temperature with different diameters were investigated.The values of Huang-Rhys factor are decreased because of ZnS component incorporating into QDs that change the structure and luminous mechanism of QDs.The main emission mechanism of the donor-acceptor pair recombination is decreased,and the recombination of surface state and conduction band to a localized energy are increased.Different number of ZnS shell for CuInSe/ZnS quantum dots were prepared by thermal injection method.We investigated their photoluminescence properties and by tuning the number of ZnS shell to tune different particle size of the quantum dots.With increasing the number of ZnS shell,the phenomenon of the spectral blue shift is more obvious.The PL lifetime and temperature-dependent photoluminescence spectroscopy of CuInSe/ZnS quantum dots were investigated to understand the internal luminescence mechanism.The emission peak position,FWHM of the PLpeak and PL Intensity of quantum dots with different diameters were investigated as a function of temperature.The values of Huang-Rhys factor are decreased because of ZnS component incorporating into QDs that change the structure of QDs.Different particle sizes of Mn doped ZnCuInS quantum dots were prepared with different reaction time by thermal injection method.Different test methods were used to reveal the successful incorporation of Mn2+ ion into ZnCuInS quantum dots for obtaining the Mn d-state emission.We investigated the temperature-dependent PL spectra of Mn doped ZnCuInS quantum dots that shown a redshift with decreasing intensity at low temperature.The emission peak position,the FWHM of the PL peak and PL Intensity of quantum dots with different diameters were investigated as a function of temperature.The fitting values of Huang-Rhys factor are much smaller shown the weak coupling regime which resulting from Mn2+(4T1?6A1)emission.