Preparation And Luminescent Properties Of ZnAgInSe Quaternary Quantum Dots

Quantum dots have aroused public attention owning to particular photometric characteristics which drawn applications for light-emitting diodes,bio-labeling,photovoltaic,photocatalytic,temperature sensor and QD lasers.Many efficient approaches have been developed to tune the luminescence spectrum of QDs recently.In this paper,ZnAgInSe quantum dots with different particle size,Znx Ag InSe quantum dots and ZnAgInSe/ZnSe quantum dots have been synthesized.The fluorescence decay lifetime and temperature dependent PL spectra have been studied to investigate the internal luminescence mechanism.The research contents are as follows:ZnAgInSe QDs with different particle size were successfully synthesised.Through changing the particle size,we have successfully tuned the optical properties of ZnAgInSe QDs.The photoluminescence was red shift with particle size increasing,which depended on quantum confinement effect.The luminescence mechanism of ZnAgInSe QDs were contributed by the three process including the conduction-band level to a localized intragap level,the surface related recombination,and the donor to acceptor recombination from the time-resolved PL study.The peak energy and PL intensity,full width as half maximum(FWHM)are also studied by measuring the temperature dependent PL spectra.Moreover,the activation energy,the average phonon energy and the Huang-Rhys factor were obtained.And the temperature-dependent nonradiative recombination was also discussed.We synthesized the quaternary ZnxAgInSe QDs with different composition ratios via a facile route.The emission peak of ZnxAgInSe QDs blueshifts at room temperature as the Zn/Ag precursor ratio increases.Meanwhile,the PL intensity increases as the Zn content of ZnxAgInSe QDs.This phenomenon reveals that,the relative change in the different recombinations was caused by the change in VZn and VAg,the increment of Zn composition induces the decrement in VAg,consequently,increment in VZn.Through the temperature dependent PL spectra,we analyze the luminescent mechanism of Znx Ag InSe QDs with different Zn/Ag ratios.We also investigate the relationship of the full width of half maximum(FWHM),energy level and fluorescence intensity in the temperature range of 10K-300 K.The decrease in the Huang-Rhys factor may be due to the thermal expansion of the crystalline network result the change in the bandgap energy.To understand the photoluminescence mechanism in ZnxAgInSe QDs,the fluorescence decay lifetime was also investigated.These findings suggest that the photoluminescence was attributed to three patterns,including conduction band-VAg recombination,surface related radiative recombination,and donor-acceptor pair(DAP)recombination.Meanwhile,it also can be used as a temperature sensor with high temperature sensitivity.We synthesized Zn AgInSe/ZnSe QDs with different number of Zn Se shell.The Photoluminescence spectrum was blue shift with increasing the number of ZnSe shell.The luminescence mechanism of ZnAgInSe/ZnSe QDs was studied from the fluorescence decay lifetime.Through temperature dependent photoluminescence spectroscopy of Zn AgInSe/ZnSe QDs,the peak energy,fluorescence intensity,full width as half maximum(FWHM)with different number of ZnSe shell in the temperature range 10-300 K were investigated.The values of Huang-Rhys factor are decreased with the increase of the number of ZnSe layers,indicating that the exciton-phonon coupling decreases.