Improved Photoluminescence Stability Of Mn²⁺ Doped CsPbCl₃ Nanocrystals Via Pb-site Sn Doping

All inorganic perovskite nanocrystals（NCs）have attracted wide attention due to their excellent optical properties and high carrier mobility,and show great potential in solar cells,light-emitting diodes（LEDs）and lasers.Among them,the new Mn²⁺doped all inorganic perovskite NCs can be used in white light devices（WLEDs）because of the larger Stokes shifts and the avoidance of self-absorption.However,it has been found that the surface ligands of Mn²⁺:CsPbCl₃ NC_S are easy to fall off,which leads to the formation of defects in NC_S and seriously reduces the optoelectronic properties of perovskite NC_S and the corresponding devices.Therefore,it is necessary to improve the thermal stability and UV radiation resistance of Mn²⁺doped all inorganic perovskite NC_S in order to promote its practical application.In this paper,a B-Sn²⁺doping strategy is used to synthesize Mn²⁺doped cesium lead chloride(Mn²⁺:CsPbCl₃)perovskite NCs.A series of Mn²⁺:CsPbCl₃ NC_S were prepared by changing the amount of Sn Cl₂ added during the growth of NC_S and adjusting the molar ratio of Sn/Mn/Pb.The structure and morphology of NC_S were characterized by X-ray diffraction（XRD）and transmission electron microscopy（TEM）.The thermal stability of NC_S thin films was studied by variable temperature photoluminescence spectroscopy.The stability of NC_S under UV irradiation was studied by UV irradiation,including absorption,photoluminescence,and time-resolved fluorescence spectroscopy.In this thesis,I first studied the improved luminescent efficiency and thermal stability of Mn²⁺:CsPbCl₃ NCs by doping Sn²⁺in B position.The analysis of elements and microstructure shows that Sn ions are successfully doped into NC_S lattice and are in a positive bivalent state.With the increase of Sn²⁺doping amount,the doping efficiency of Mn²⁺is improved,and the luminous intensity of NC_S is enhanced.When the molar ratio of Sn/Mn/Pb is 1/1/1,the best synthesis process of Mn²⁺:CsPbCl₃ NC_S is obtained,and its photoluminescence quantum efficiency（PL QY）is 43%.When the temperature is higher than 20°C,the incorporation of Sn²⁺can obviously slow down the luminescent quenching of Mn²⁺ions,the thermal quenching temperature of NCs reaches 80°C.The PL spectra and fluorescence lifetimes of Mn²⁺:CsPbCl₃ NCs under different UV irradiation time were measured.On increasing the ultraviolet illumination time,almost unchanged single exponential decay times of the Mn²⁺emissions and slow reduction in the PL intensities of Mn²⁺:CsPbCl₃ NCs after Sn doping were found,indicating that Sn doping could significantly improve the ultraviolet irradiation stability of Mn²⁺:CsPbCl₃ NCs.