Study On Spectral Properties Of All-inorganic Perovskite Nano-spheres

Perovskite materials generally refer to substances having a face-centered cubic structure similar to ABX₃,the material of this type of crystal structure was proposed by the Russian mineralogist Lev Perovski in 1939 to study perovskite,because of their excellent physical and chemical properties,such as high carrier mobility,high absorption coefficient,high quantum yield and low trap state density,they are used in solar cells,luminescent materials,lasers and photovoltaics.In the study of this paper,we have synthesized the inorganic inorganic perovskite CsPbBr₃ nanospheres and CsPbI₃ nanospheres by chemical vapor deposition?CVD?,and analyzed the optical properties of this material.There are two main parts:1.Obvious fluorescence scintillation was observed on CsPbBr₃ NSs.This phenomenon is totally different from the previous phenomena observed on quantum dots.The scintillation frequency is several orders of magnitude faster than the scintillation frequency observed on quantum dots,and its duration of bright and dark states is 0.1s⁰.7s,which is much lower than the quantums dots bright/dark state for a few seconds to tens of seconds.which may indicate a different scintillation mechanism from quantum dots.We find that the scintillation of nanospheres with different sizes is obviously different,and the scintillation is obviously suppressed with the increase of sample size,which is attributed to the average fluorescence effect by the different size of nanospheres from that of quantum dots.We believe that surface defects of nanospheres cause fluorescence scintillation by trapping electrons,which is explained in detail by the schematic diagram.This defect originates from the chemical or structural defects of the sample itself and is closely related to the ambient atmosphe-re around the sample.This metastable defect causes fluorescence intensity fluctuation of large-scale samples at the scale of 100 milliseconds.The delayed fluorescence in the scintillation state is in good agreement with the schematic diagram proposed by us.We further passivated the sample surface to achieve the purpose of suppressing scintillation.2.We synthesized high-quality inorganic CSPbBr₃ NSs and CsPbI₃ NSs by chemical vapor deposition.By virtue of the nearly perfect spherical structure formed by material morphology,we obtained an echo-wall optical microcavity?WGM?,which can confine the light length to a very small volume for a long time,and make the light and matter interact strongly,so as to control the electromagnetic field.Local density of states enhances or suppresses the spontaneous emission of atoms.So we have obtained a single-mode laser with high quality factor on this optical microcavity.For CsPbBr₃ NSs and CsPbI₃ NSs,they have low thresholds(⁴.77 Jcm^-2 and⁹3.84Jcm^-2),narrow half-peak width?⁰.14 and⁰.21 nm?and high Q factors?³800 and³400?.Then we simulate the light field distribution in nanospheres by finite difference time domain?FDTD?.The simulation results show that the perfect Echo Wall mode is formed by the full emission of light in the cavity,and high quality single-mode laser is obtained.Finally,we explored the obvious spectral broadening and blue shift of CsPbBr₃ NSs and CsPbI₃ NSs under high power excitation.It is found that the spectral broadening and blue shifting properties of CsPbBr₃ NSs and CsPbI₃ NSs are significantly different.The broadening and blue shift are mainly due to Different pump powers cause a sharp change in the carrier density in the sample,and a change in the carrier density causes a change in the relative refractive index of the sample.